1.
German language
–
German is a West Germanic language that is mainly spoken in Central Europe. It is the most widely spoken and official language in Germany, Austria, Switzerland, South Tyrol, the German-speaking Community of Belgium and it is also one of the three official languages of Luxembourg. Major languages which are most similar to German include other members of the West Germanic language branch, such as Afrikaans, Dutch, English, Luxembourgish and it is the second most widely spoken Germanic language, after English. One of the languages of the world, German is the first language of about 95 million people worldwide. The German speaking countries are ranked fifth in terms of publication of new books. German derives most of its vocabulary from the Germanic branch of the Indo-European language family, a portion of German words are derived from Latin and Greek, and fewer are borrowed from French and English. With slightly different standardized variants, German is a pluricentric language, like English, German is also notable for its broad spectrum of dialects, with many unique varieties existing in Europe and also other parts of the world. The history of the German language begins with the High German consonant shift during the migration period, when Martin Luther translated the Bible, he based his translation primarily on the standard bureaucratic language used in Saxony, also known as Meißner Deutsch. Copies of Luthers Bible featured a long list of glosses for each region that translated words which were unknown in the region into the regional dialect. Roman Catholics initially rejected Luthers translation, and tried to create their own Catholic standard of the German language – the difference in relation to Protestant German was minimal. It was not until the middle of the 18th century that a widely accepted standard was created, until about 1800, standard German was mainly a written language, in urban northern Germany, the local Low German dialects were spoken. Standard German, which was different, was often learned as a foreign language with uncertain pronunciation. Northern German pronunciation was considered the standard in prescriptive pronunciation guides though, however, German was the language of commerce and government in the Habsburg Empire, which encompassed a large area of Central and Eastern Europe. Until the mid-19th century, it was essentially the language of townspeople throughout most of the Empire and its use indicated that the speaker was a merchant or someone from an urban area, regardless of nationality. Some cities, such as Prague and Budapest, were gradually Germanized in the years after their incorporation into the Habsburg domain, others, such as Pozsony, were originally settled during the Habsburg period, and were primarily German at that time. Prague, Budapest and Bratislava as well as cities like Zagreb, the most comprehensive guide to the vocabulary of the German language is found within the Deutsches Wörterbuch. This dictionary was created by the Brothers Grimm and is composed of 16 parts which were issued between 1852 and 1860, in 1872, grammatical and orthographic rules first appeared in the Duden Handbook. In 1901, the 2nd Orthographical Conference ended with a standardization of the German language in its written form
German language
–
Old Frisian (Alt-Friesisch)
German language
–
The widespread popularity of the
Bible translated into German by
Martin Luther helped establish modern German
German language
–
Examples of German language in
Namibian everyday life
German language
–
German-language newspapers in the U.S. in 1922
2.
Sandstone
–
Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earths crust, like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, quartz-bearing sandstone is converted into quartzite through heating and pressure, usually related to tectonic compression within orogenic belts. They are formed from cemented grains that may either be fragments of a rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, grain sizes in sands are defined within the range of 0.0625 mm to 2 mm. The formation of sandstone involves two principal stages, first, a layer or layers of sand accumulates as the result of sedimentation, either from water or from air. Typically, sedimentation occurs by the settling out from suspension. The most common cementing materials are silica and calcium carbonate, which are derived either from dissolution or from alteration of the sand after it was buried. Colours will usually be tan or yellow, a predominant additional colourant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red, with additional manganese imparting a purplish hue. Red sandstones are seen in the Southwest and West of Britain, as well as central Europe. The regularity of the latter favours use as a source for masonry, either as a building material or as a facing stone. These physical properties allow the grains to survive multiple recycling events. Quartz grains evolve from rock, which are felsic in origin. Feldspathic framework grains are commonly the second most abundant mineral in sandstones, Feldspar can be divided into two smaller subdivisions, alkali feldspars and plagioclase feldspars. The different types of feldspar can be distinguished under a petrographic microscope, below is a description of the different types of feldspar. Alkali feldspar is a group of minerals in which the composition of the mineral can range from KAlSi3O8 to NaAlSi3O8. Plagioclase feldspar is a group of solid solution minerals that range in composition from NaAlSi3O8 to CaAl2Si2O8. Lithic framework grains are pieces of ancient source rock that have yet to weather away to individual mineral grains, accessory minerals are all other mineral grains in a sandstone, commonly these minerals make up just a small percentage of the grains in a sandstone
Sandstone
–
Cut slab of sandstone showing
Liesegang banding
Sandstone
–
Devonian Sandstone at Suur Taevaskoda,
Põlva County,
Estonia
Sandstone
–
Alcove in the
Navajo Sandstone
Sandstone
–
Sandstone Rock-cut tombs (
Kokhim) in
Petra,
Jordan
3.
Quartz
–
Quartz is the second most abundant mineral in Earths continental crust, behind feldspar. There are many different varieties of quartz, several of which are semi-precious gemstones, since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. The word quartz is derived from the German word Quarz and its Middle High German ancestor twarc, the Ancient Greeks referred to quartz as κρύσταλλος derived from the Ancient Greek κρύος meaning icy cold, because some philosophers apparently believed the mineral to be a form of supercooled ice. Today, the rock crystal is sometimes used as an alternative name for the purest form of quartz. Quartz belongs to the crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end, well-formed crystals typically form in a bed that has unconstrained growth into a void, usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, a quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward. α-quartz crystallizes in the crystal system, space group P3121 and P3221 respectively. β-quartz belongs to the system, space group P6222 and P6422. These space groups are truly chiral, both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks. The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is an identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent, common colored varieties include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others. The most important distinction between types of quartz is that of macrocrystalline and the microcrystalline or cryptocrystalline varieties, the cryptocrystalline varieties are either translucent or mostly opaque, while the transparent varieties tend to be macrocrystalline. Chalcedony is a form of silica consisting of fine intergrowths of both quartz, and its monoclinic polymorph moganite. Other opaque gemstone varieties of quartz, or mixed rocks including quartz, often including contrasting bands or patterns of color, are agate, carnelian or sard, onyx, heliotrope, amethyst is a form of quartz that ranges from a bright to dark or dull purple color. The worlds largest deposits of amethysts can be found in Brazil, Mexico, Uruguay, Russia, France, Namibia, sometimes amethyst and citrine are found growing in the same crystal. It is then referred to as ametrine, an amethyst is formed when there is iron in the area where it was formed
Quartz
–
Quartz
crystal cluster from
Tibet
Quartz
–
Clear rock crystals on a white base
Quartz
–
Amethyst crystals on matrix
Quartz
–
Citrine from Brazil
4.
Feldspar
–
Feldspars are a group of rock-forming tectosilicate minerals that make up about 40% of the Earths continental crust. Feldspars crystallize from magma as veins in both intrusive and extrusive rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of plagioclase feldspar is known as anorthosite. Feldspars are also found in types of sedimentary rocks. The name feldspar derives from the German Feldspat, a compound of the words Feld, field, and Spat, the change from Spat to -spar was influenced by the English word spar, a synonym for mineral. Feldspathic refers to materials that contain feldspar, the alternate spelling, felspar, has largely fallen out of use. This group of minerals consists of tectosilicates, solid solutions between albite and anorthite are called plagioclase, or more properly plagioclase feldspar. Only limited solid solution occurs between K-feldspar and anorthite, and in the two solid solutions, immiscibility occurs at temperatures common in the crust of the earth. Albite is considered both a plagioclase and alkali feldspar, the alkali feldspars are as follows, orthoclase —KAlSi3O8 sanidine —AlSi3O8 microcline —KAlSi3O8 anorthoclase —AlSi3O8 Sanidine is stable at the highest temperatures, and microcline at the lowest. Perthite is a texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye, microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope. Barium feldspars are also considered alkali feldspars, barium feldspars form as the result of the substitution of barium for potassium in the mineral structure. The barium feldspars are monoclinic and include the following, celsian—BaAl2Si2O8 hyalophane—4O8 The plagioclase feldspars are triclinic, the immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colours visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae, chemical weathering of feldspars results in the formation of clay minerals. About 20 million tonnes of feldspar were produced in 2010, mostly by three countries, Italy, Turkey, and China, Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as a filler and extender in paint, plastics, and rubber. In glassmaking, alumina from feldspar improves product hardness, durability, in ceramics, the alkalis in feldspar act as a flux, lowering the melting temperature of a mixture. Fluxes melt at a stage in the firing process, forming a glassy matrix that bonds the other components of the system together. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers, ceramics and other uses, such as fillers, accounted for the remainder
Feldspar
–
Feldspar crystal (18×21×8.5 cm) from
Jequitinhonha valley,
Minas Gerais, Southeastern Brazil.
Feldspar
–
Compositional phase diagram of the different minerals that constitute the feldspar solid solution.
Feldspar
–
Lunar ferrous
anorthosite #60025 (
plagioclase feldspar). Collected by
Apollo 16 from the
Lunar Highlands near
Descartes Crater. This sample is currently on display at the
National Museum of Natural History in
Washington, D.C.
Feldspar
–
Labradorite.
5.
Lithic Fragment (geology)
–
Lithic fragments, or lithics, are pieces of other rocks that have been eroded down to sand size and now are sand grains in a sedimentary rock. They were first described and named by Bill Dickinson in 1970, lithic fragments can be derived from sedimentary, igneous or metamorphic rocks). A lithic fragment is defined using the Gazzi-Dickinson point-counting method and being in the sand-size fraction, sand grains in sedimentary rocks that are fragments of larger rocks that are not identified using the Gazzi-Dickinson method are usually called rock fragments instead of lithic fragments. Sandstones rich in lithic fragments are called lithic sandstones and these can include granular, microlitic, lathwork, and vitric. These correlations between composition and volcanic lithic fragment type are approximate, at best, by definition, intrusive igneous rock fragments can not be considered lithic fragments. These can include shale siltstone fragments, and chert and these can include fine-grained schist and phyllite fragments, among others
Lithic Fragment (geology)
–
Granular volcanic lithic fragment, scale in
millimeters Top picture in plane-
polarized light, bottom picture in cross-polarized light.
Lithic Fragment (geology)
–
Microlitic volcanic lithic fragment, scale in millimeters. Top picture in plane-polarized light, bottom picture in cross-polarized light.
Lithic Fragment (geology)
–
Lathwork volcanic lithic fragment, scale in millimeters. Top picture in plane-polarized light, bottom picture in cross-polarized light.
6.
Clay
–
Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to water content and become hard, brittle. Depending on the content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size, silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in size and other physical properties. The distinction between silt and clay varies by discipline, geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm, sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils Atterberg limits, ISO14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. These solvents, usually acidic, migrate through the rock after leaching through upper weathered layers. In addition to the process, some clay minerals are formed through hydrothermal activity. There are two types of deposits, primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation, secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are associated with very low energy depositional environments such as large lakes. Depending on the source, there are three or four main groups of clays, kaolinite, montmorillonite-smectite, illite, and chlorite. Chlorites are not always considered to be a clay, sometimes being classified as a group within the phyllosilicates. There are approximately 30 different types of clays in these categories. Varve is clay with visible annual layers, which are formed by deposition of those layers and are marked by differences in erosion. This type of deposit is common in glacial lakes
Clay
–
Gay Head cliffs in
Martha's Vineyard consist almost entirely of clay.
Clay
–
Electron microscope photograph of smectite clay – magnification 23,500
Clay
–
Quaternary clay in
Estonia
Clay
–
Deforestation for clay extraction in
Rio de Janeiro,
Brazil. The picture is of Morro da Covanca, Jacarepaguá.
7.
Sedimentary rock
–
Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earths surface and within bodies of water. Sedimentation is the name for processes that cause mineral and/or organic particles to settle in place. The particles that form a rock by accumulating are called sediment. Sedimentation may also occur as minerals precipitate from solution or shells of aquatic creatures settle out of suspension. The sedimentary rock cover of the continents of the Earths crust is extensive, sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding, sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores. The study of the sequence of rock strata is the main source for an understanding of the Earths history, including palaeogeography, paleoclimatology. The scientific discipline that studies the properties and origin of rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geomorphology, geochemistry, sedimentary rocks have also been found on Mars. Clastic sedimentary rocks are composed of rock fragments that were cemented by silicate minerals. Clastic rocks are composed largely of quartz, feldspar, rock fragments, clay minerals, and mica, any type of mineral may be present, clastic sedimentary rocks, are subdivided according to the dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions, gravel, sand, and mud and this tripartite subdivision is mirrored by the broad categories of rudites, arenites, and lutites, respectively, in older literature. The subdivision of these three categories is based on differences in clast shape, conglomerates and breccias), composition. Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel, composition of framework grains The relative abundance of sand-sized framework grains determines the first word in a sandstone name. Naming depends on the dominance of the three most abundant components quartz, feldspar, or the lithic fragments that originated from other rocks, all other minerals are considered accessories and not used in the naming of the rock, regardless of abundance. Clean sandstones with open space are called arenites. Muddy sandstones with abundant muddy matrix are called wackes, six sandstone names are possible using the descriptors for grain composition and the amount of matrix. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles and these relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as the flow calms and the particles settle out of suspension
Sedimentary rock
–
Middle
Triassic marginal marine sequence of siltstones (reddish layers at the cliff base) and limestones (brown rocks above),
Virgin Formation, southwestern
Utah, USA
Sedimentary rock
–
Sedimentary rocks on Mars, investigated by NASA's
Curiosity Mars rover
Sedimentary rock
–
Steeply dipping sedimentary rock strata along the
Chalous Road in northern
Iran
Sedimentary rock
–
Claystone deposited in
Glacial Lake Missoula,
Montana,
United States. Note the very fine and flat bedding, common for distal
lacustrine deposition.
8.
Paleozoic
–
The Paleozoic Era is the earliest of three geologic eras of the Phanerozoic Eon, from 541 to 252.17 million years ago. It is the longest of the Phanerozoic eras, and is subdivided into six periods, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous. The Paleozoic comes after the Neoproterozoic era of the Proterozoic and is followed by the Mesozoic, the Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earths history, known as the Cambrian explosion, fish, arthropods, amphibians, anapsids, synapsids, euryapsids and diapsids all evolved during the Paleozoic. Life began in the ocean but eventually transitioned onto land, and by the late Paleozoic, Great forests of primitive plants covered the continents, many of which formed the coal beds of Europe and eastern North America. Towards the end of the era, large, sophisticated diapsids and synapsids were dominant, the Paleozoic Era ended with the largest extinction event in the history of Earth, the Permian–Triassic extinction event. The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover, recovery of life in the sea may have been much faster. The Paleozoic era began and ended with supercontinents and in between were the rise of mountains along the margins, and flooding and draining of shallow seas between. At its start, the supercontinent Pannotia broke up, paleoclimatic studies and evidence of glaciers indicate that central Africa was most likely in the polar regions during the early Paleozoic. During the early Paleozoic, the huge continent Gondwana formed or was forming, by mid-Paleozoic, the collision of North America and Europe produced the Acadian-Caledonian uplifts, and a subduction plate uplifted eastern Australia. There are six periods in the Paleozoic Era, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, the Cambrian spans from 541 million years to 485 million years and is the first period of the Paleozoic era of the Phanerozoic. The Cambrian marked a boom in evolution in an event known as the Cambrian explosion in which the largest number of creatures evolved in any period of the history of the Earth. Creatures like algae evolved, but the most ubiquitous of that period were the armored arthropods, almost all marine phyla evolved in this period. During this time, the supercontinent Pannotia begins to break up, the Ordovician spanned from 485 million years to 443 million years ago. The Ordovician is a time in Earths history in many of the biological classes still prevalent today evolved, such as primitive fish, cephalopods. The most common forms of life, however, were trilobites, snails, more importantly, the first arthropods went ashore to colonize the empty continent of Gondwana. By the end of the Ordovican, Gondwana was at the pole, early North America had collided with Europe. Glaciation of Africa resulted in a drop in sea level
Paleozoic
–
Trilobites
Paleozoic
–
Cephalaspis (a jawless fish)
Paleozoic
–
Eogyrinus (an amphibian) of the Carboniferous
Paleozoic
–
Dimetrodon
9.
Stratum
–
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers. The stratum is the unit in a stratigraphic column and forms the basis of the study of stratigraphy. Each layer is one of a number of parallel layers that lie one upon another. They may extend over hundreds of thousands of kilometers of the Earths surface. Strata are typically seen as bands of different colored or differently structured material exposed in cliffs, road cuts, quarries, individual bands may vary in thickness from a few millimeters to a kilometer or more. Each band represents a mode of deposition, river silt, beach sand, coal swamp, sand dune, lava bed. Geologists study rock strata and categorize them by the material of beds, each distinct layer is typically assigned to the name of sheet, usually based on a town, river, mountain, or region where the formation is exposed and available for study. For example, the Burgess Shale is an exposure of dark, occasionally fossiliferous. Slight distinctions in material in a formation may be described as members, formations are collected into groups while groups may be collected into supergroups. Archaeological horizon Geologic formation Geologic map Geologic unit Law of superposition Bed GeoWhen Database
Stratum
–
Strata in
Salta (
Argentina).
Stratum
–
Goldenville strata in quarry in
Bedford,
Canada. These are
Middle Cambrian marine sediments. This formation covers over half of
Nova Scotia and is recorded as being 29,000 feet thick in some areas.
Stratum
Stratum
10.
Particle size (grain size)
–
Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials and this is different from the crystallite size, which refers to the size of a single crystal inside a particle or grain. A single grain can be composed of several crystals, granular material can range from very small colloidal particles, through clay, silt, sand, gravel, and cobbles, to boulders. Size ranges define limits of classes that are given names in the Wentworth scale used in the United States, the Krumbein phi scale, a modification of the Wentworth scale created by W. C. This equation can be rearranged to find diameter using φ, D = D0 ×2 − ϕ In some schemes, ISO 14688-1 is applicable to natural soils in situ, similar man-made materials in situ and soils redeposited by people. An accumulation of sediment can also be characterized by the size distribution. A sediment deposit can undergo sorting when a particle size range is removed by an agency such as a river or the wind, a Scale of Grade and Class Terms for Clastic Sediments
Particle size (grain size)
–
Wentworth grain size chart from United States Geological Survey Open-File Report 2006-1195
Particle size (grain size)
–
Beach cobbles (gravel) at Nash Point, South Wales.
Particle size (grain size)
11.
Matrix (geology)
–
The matrix or groundmass of rock is the finer-grained mass of material wherein larger grains, crystals or clasts are embedded. The matrix of an igneous rock consists of finer-grained, often microscopic and this porphyritic texture is indicative of multi-stage cooling of magma. For example, porphyritic andesite will have large phenocrysts of plagioclase in a fine-grained matrix, also in South Africa, diamonds are often mined from a matrix of weathered clay-like rock called yellow ground. The matrix of sedimentary rocks is finer-grained sedimentary material, such as clay or silt and it also used to describe the rock material in which a fossil is embedded. All sediments are at first in an incoherent condition, and in this state they may remain for an indefinite period. Millions of years have elapsed since some of the early Tertiary strata gathered on the floor, yet they are quite friable. The pressure of newer sediments on underlying masses is one cause of this change. More efficiency is generally ascribed to the action of percolating water, the redeposited cementing material is most commonly calcareous or siliceous. Limestones, which were originally a loose accumulation of shells, corals, the change of aragonite to calcite and of calcite to dolomite, by forming new crystalline masses in the interior of the rock, usually also accelerates consolidations. Silica is less soluble in ordinary waters, but even this ingredient of rocks is dissolved and redeposited with great frequency. Others contain fine scales of kaolin or of mica, argillaceous materials may be compacted by mere pressure, like graphite and other scaly minerals
Matrix (geology)
–
Potassium feldspar phenocrysts within a fine grained matrix in a
granite porphyry.
12.
Turbidity current
–
A turbidity current is most typically an underwater current of usually rapidly moving, sediment-laden water moving down a slope. Turbidity currents can occur in other fluids besides water. In the most typical case of oceanic turbidity currents, sediment laden waters situated over sloping ground will flow down-hill because they have a higher density than the adjacent waters. The driving force behind a turbidity current is gravity acting on the density of the sediments temporarily suspended within a fluid. These semi-suspended solids make the density of the sediment bearing water greater than that of the surrounding. As such currents flow, they often have a snow-balling-effect, as they stir up the ground over which they flow and their passage leaves the ground over which they flow scoured and eroded. Once an oceanic turbidity current reaches the waters of the flatter area of the abyssal plain. The sedimentary deposit of a turbidity current is called a turbidite, examples of turbidity currents involving other fluid mediums besides liquid water include, avalanches, lahars, pyroclastic flows, and lava flows. Seafloor turbidity currents are often the result of sediment-laden river outflows and they are characterized by a well-defined advance-front, also known as the currents head, and are followed by the currents main body. In terms of the often observed and more familiar above sea-level phenomenon. With an increasing continental shelf slope, current velocity increases, as the velocity of the flow increases, turbulence increases, the increase in sediment also adds to the density of the current, and thus its velocity even further. Turbidity currents are traditionally defined as those sediment gravity flows in which sediment is suspended by fluid turbulence, however, the term turbidity current was adopted to describe a natural phenomenon whose exact nature is often unclear. Definitions are further complicated by an understanding of the turbulence structure within turbidity currents. A turbidity current is a current in which the interstitial fluid is a liquid. The average concentration of suspended sediment for most river water enters the ocean is much lower than the sediment concentration needed for entry as a hyperpycnal plume. Although some rivers can often have high sediment load that can create a continuous hyperpycnal plume, such as the Haile River. The sediment concentration needed to produce a plume in marine water is 35 to 45 kg/m³. Most rivers produce hyperpycnal flows only during events, such as storms, floods, glacier outbursts, dam breaks
Turbidity current
–
An example of steep submarine canyons carved out by turbidity currents, located along
California 's central Coast.
Turbidity current
–
Turbidite
interbedded with finegrained dusky-yellow
sandstone and gray
clay shale that occur in graded beds,
Point Loma Formation, California.
13.
Turbidite
–
A turbidite is the geologic deposit of a turbidity current, which is a type of sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Turbidites were first properly described by Arnold H and this vertical succession of sedimentary structures, bedding, and changing lithology is representative of strong to waning flow regime currents and their corresponding sedimentation. It is unusual to see all of a complete Bouma cycle and it is now recognized that the vertical progression of sedimentary structures described by Bouma applies to turbidites deposited by low-density turbidity currents. As the sand concentration of a flow increases, grain-to-grain collisions within the turbid suspension create dispersive pressures that become important in hindering further settling of grains, as a consequence, a slightly different set of sedimentary structures develops in turbidites deposited by high-density turbidity currents. This different set of structures is known as the Lowe sequence, which is a classification that complements, but does not replace. Turbidites are sediments which are transported and deposited by density flow, the distinction is that, in a normal river or stream bed, particles of rock are carried along by frictional drag of water on the particle. The water must be travelling at a velocity in order to suspend the particle in the water. The greater the size or density of the relative to the fluid in which it is travelling. Density based flow, however, occurs when liquefaction of sediment during transport causes a change to the density of the fluid and this is usually achieved by highly turbulent liquids which have a suspended load of fine grained particles forming a slurry. In this case, larger fragments of rock can be transported at water velocities too low to otherwise do so because of the density contrast. This condition occurs in many environments aside from simply the deep ocean, turbidites in sediments can occur in carbonate as well as siliciclastic sequences. A different vertical progression of sedimentary structures characterize high-density turbidites, massive accumulations of turbidites and other deep water deposits may result in the formation of submarine fans. Density currents may be triggered in areas of sediment supply by gravitational failure alone. Turbidites can represent a high record of seismicity, and terrestrial storm/flood events depending on the connectivity of canyon/channel systems to terrestrial sediment sources. Proterozoic gold deposits are known from turbidite basin deposits. Turbidite deposits typically occur in foreland basins, the Encyclopedia of Oceanography, Encyclopedia of earth sciences series 1, Van Nostrand Reinhold Company, New York, p. 945–946. Morey, A. Johnson, J. E. Gutierrez-Pastor, J. Eriksson, mutti, E. & Ricci Lucci, F. Turbidite facies and facies associations. In, Examples of turbidite facies and associations from selected formations of the northern Apennines, congress of Sedimentology, Field Trip A-11, p. 21–36
Turbidite
–
Turbidite sequence.
Carboniferous Ross
Sandstone Formation (
Namurian),
County Clare, Western
Ireland (
USGS image).
Turbidite
–
Complete Bouma sequence in Devonian Sandstone (Becke-Oese,
Germany).
Turbidite
–
Gorgoglione
Flysch, Miocene, South Italy
14.
Sedimentation
–
Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the acting on them. In geology, sedimentation is often used as the opposite of erosion, in that sense, it includes the termination of transport by saltation or true bedload transport. Settling is the falling of suspended particles through the liquid, whereas sedimentation is the termination of the settling process, in estuarine environments, settling can be influenced by the presence or absence of vegetation. Trees such as mangroves are crucial to the attenuation of waves or currents, even small molecules supply a sufficiently strong force to produce significant sedimentation. This process is used in the biotech industry to separate cells from the culture media. In a sedimentation experiment, the applied force accelerates the particles to a velocity v t e r m at which the applied force is exactly canceled by an opposing drag force. For small enough particles, the force varies linearly with the terminal velocity, i. e. F d r a g = f v t e r m where f depends only on the properties of the particle. Thus, measuring s can reveal underlying properties of the particle, in many cases, the motion of the particles is blocked by a hard boundary, the resulting accumulation of particles at the boundary is called a sediment. The concentration of particles at the boundary is opposed by the diffusion of the particles, the sedimentation of a single particle under gravity is described by the Mason–Weaver equation, which has a simple exact solution. The sedimentation coefficient s in this case equals m b / f, the sedimentation of a single particle under centrifugal force is described by the Lamm equation, which likewise has an exact solution. The sedimentation coefficient s also equals m b / f, where m b is the buoyant mass, the Lamm equation also has extra terms, since it pertains to sector-shaped cells, whereas the Mason–Weaver equation is one-dimensional. They settle as individual particles and do not flocculate or stick to other during settling, example, alum or iron coagulation Type 3 sedimentation is also known as zone sedimentation. In this process the particles are at a high concentration such that the particles tend to settle as a mass, zone settling occurs in lime-softening, sedimentation, active sludge sedimentation and sludge thickeners. In geology, sedimentation is the deposition of particles carried by a fluid flow, for suspended load, this can be expressed mathematically by the Exner equation, and results in the formation of depositional landforms and the rocks that constitute sedimentary record. An undesired increased transport and sedimentation of suspended material is called siltation, high sedimentation rates can be a result of poor land management and a high frequency of flooding events. If not managed properly, it can be detrimental to fragile ecosystems on the receiving end, climate change also affects siltation rates. In chemistry, sedimentation has been used to measure the size of large molecules, where the force of gravity is augmented with centrifugal force in an ultracentrifuge
Sedimentation
–
Siltation
15.
Gravel
–
Gravel /ˈɡrævəl/ is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel is categorized by the Udden-Wentworth scale into granular gravel and pebble gravel, one cubic metre of gravel typically weighs about 1,800 kg. Gravel is an important commercial product, with a number of applications, many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or tarmac, both sand and small gravel are also important for the manufacture of concrete. Large gravel deposits are a geological feature, being formed as a result of the weathering. The action of rivers and waves tends to pile up gravel in large accumulations and this can sometimes result in gravel becoming compacted and concreted into the sedimentary rock called conglomerate. Where natural gravel deposits are insufficient for human purposes, gravel is often produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, quarries where gravel is extracted are known as gravel pits. Southern England possesses particularly large concentrations of them due to the deposition of gravel in the region during the Ice Ages. As of 2006, the United States is the leading producer and consumer of gravel. The word gravel comes from the Breton language, adding the -el suffix in Breton denotes the component parts of something larger. Thus gravel means the stones which make up such a beach on the coast. Many dictionaries ignore the Breton language, citing Old French gravele or gravelle, Gravel often has the meaning a mixture of different size pieces of stone mixed with sand and possibly some clay. American English also allows small stones without sand mixed in also known as crushed stone, types of gravel include, Bank gravel, naturally deposited gravel intermixed with sand or clay found in and next to rivers and streams. Also known as Bank run or River run, bench gravel, a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level. Creek rock, this is rounded, semi-polished stones, potentially of a wide range of types. It is also used as concrete aggregate and less often as a paving surface. Crushed stone, rock crushed and graded by screens and then mixed to a blend of stones and fines and it is widely used as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may be made from granite, limestone, dolomite, also known as crusher run, DGA QP, and shoulder stone
Gravel
–
Gravel (largest fragment in this photo is about 4 cm)
Gravel
–
A
gravel road in
Terre Haute, Indiana
Gravel
–
Gravel being unloaded from a
barge
Gravel
–
Gravel with stones sized roughly between 5 and 15 mm
16.
Sand
–
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt, Sand can also refer to a textural class of soil or soil type, i. e. a soil containing more than 85% sand-sized particles by mass. The second most common type of sand is calcium carbonate, for example aragonite, for example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean. Sand is a non renewable resource over human timescales, and sand suitable for making concrete is in high demand, in terms of particle size as used by geologists, sand particles range in diameter from 0.0625 mm to 2 mm. An individual particle in this size is termed a sand grain. Sand grains are between gravel and silt, a 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A1938 specification of the United States Department of Agriculture was 0.05 mm. Sand feels gritty when rubbed between the fingers. ISO14688 grades sands as fine, medium and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the United States, sand is commonly divided into five sub-categories based on size, very fine sand, fine sand, medium sand, coarse sand, and very coarse sand. These sizes are based on the Krumbein phi scale, where size in Φ = -log2D, on this scale, for sand the value of Φ varies from −1 to +4, with the divisions between sub-categories at whole numbers. The composition of sand is highly variable, depending on the local rock sources. The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a granitic rock outcrop. Some sands contain magnetite, chlorite, glauconite or gypsum, Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian. Chlorite-glauconite bearing sands are typically green in color, as are sands derived from basaltic with a high olivine content, many sands, especially those found extensively in Southern Europe, have iron impurities within the quartz crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain garnets and other resistant minerals, the study of individual grains can reveal much historical information as to the origin and kind of transport of the grain. Quartz sand that is weathered from granite or gneiss quartz crystals will be angular. It is called grus in geology or sharp sand in the trade where it is preferred for concrete. Sand that is transported long distances by water or wind will be rounded, people who collect sand as a hobby are known as arenophiles
Sand
–
Sand
dunes in the
Idehan Ubari, Libya.
Sand
–
Close-up (1×1 cm) of sand from the
Gobi Desert, Mongolia.
Sand
–
Heavy minerals (dark) in a quartz beach sand (
Chennai, India).
Sand
–
Sand from
Coral Pink Sand Dunes State Park,
Utah. These are grains of
quartz with a
hematite coating providing the orange color.
17.
Mud
–
A MUD, is a multiplayer real-time virtual world, usually text-based. MUDs combine elements of role-playing games, hack and slash, player versus player, interactive fiction, players can read or view descriptions of rooms, objects, other players, non-player characters, and actions performed in the virtual world. Players typically interact with other and the world by typing commands that resemble a natural language. Traditional MUDs implement a video game set in a fantasy world populated by fictional races and monsters. The objective of this sort of game is to slay monsters, explore a world, complete quests, go on adventures, create a story by roleplaying. Many MUDs were fashioned around the rules of the Dungeons & Dragons series of games. MUDs have attracted the interest of scholars from many fields, including communications, sociology, law. At one time, there was interest from the United States military in using them for teleconferencing, most MUDs are run as hobbies and are free to players, some may accept donations or allow players to purchase virtual items, while others charge a monthly subscription fee. MUDs can be accessed via standard telnet clients, or specialized MUD clients which are designed to improve the user experience, numerous games are listed at various web portals, such as The Mud Connector. Indeed, before the invention of the term MMORPG, games of this style were simply called graphical MUDs, a number of influential MMORPG designers began as MUD developers and/or players or were involved with early MUDs. Colossal Cave Adventure, created in 1975 by Will Crowther on a DEC PDP-10 computer, was the first widely used adventure game, the game was significantly expanded in 1976 by Don Woods. Also called Adventure, it contained many D&D features and references, numerous graphical MUDs were created on the PLATO system at the University of Illinois and other American universities that used PLATO, beginning in 1975. Among them were pedit5, oubliette, moria, avathar, krozair, dungeon, dnd, crypt, PLATO MUDs are often ignored by historians and by the creators of other MUDs whose work came later. Inspired by Adventure, a group of students at MIT in the summer of 1977 wrote a game for the PDP-10 minicomputer, called Zork, Zork was ported, under the filename DUNGEN, to FORTRAN by a programmer working at DEC in 1978. In 1978 Roy Trubshaw, a student at Essex University in the UK and he named the game MUD, in tribute to the Dungeon variant of Zork, which Trubshaw had greatly enjoyed playing. Trubshaw converted MUD to BCPL, before handing over development to Richard Bartle, the game revolved around gaining points till one achieved the Wizard rank, giving the character immortality and special powers over mortals. It became the first Internet multiplayer online role-playing game in 1980, the original MUD game was closed down in late 1987, reportedly under pressure from CompuServe, to whom Richard Bartle had licensed the game. This left MIST, a derivative of MUD1 with similar gameplay, as the only remaining MUD running on the Essex University network, MIST ran until the machine that hosted it, a PDP-10, was superseded in early 1991
Mud
–
A combat in
The Shadow of Yserbius, an early graphical MUD
Mud
18.
Geologist
–
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes that shape it. Geologists usually study geology, although backgrounds in physics, chemistry, biology, field work is an important component of geology, although many subdisciplines incorporate laboratory work. Some geologists work in the mining business searching for metals, oils and they are also in the forefront of natural hazards and disasters prevention and mitigation, studying natural hazards such as earthquakes, volcanic activity, tsunamis, weather storms. Their studies are used to warn the public of the occurrence of these events. Geologists are also important contributors to climate change discussions, james Hutton is often viewed as the first modern geologist. In 1785 he presented a paper entitled Theory of the Earth to the Royal Society of Edinburgh, Hutton published a two-volume version of his ideas in 1795. The first geological map of the U. S. was produced in 1809 by William Maclure, in 1807, Maclure commenced the self-imposed task of making a geological survey of the United States. Almost every state in the Union was traversed and mapped by him and this antedates William Smiths geological map of England by six years, although it was constructed using a different classification of rocks. Sir Charles Lyell first published his famous book, Principles of Geology and this book, which influenced the thought of Charles Darwin, successfully promoted the doctrine of uniformitarianism. This theory states that slow geological processes have occurred throughout the Earths history and are still occurring today, in contrast, catastrophism is the theory that Earths features formed in single, catastrophic events and remained unchanged thereafter. Though Hutton believed in uniformitarianism, the idea was not widely accepted at the time, most geologists also need skills in GIS and other mapping techniques. Geology students often spend portions of the year, especially the summer though sometimes during a January term, geologists may concentrate their studies or research in one or more of the following disciplines, Dendrochronology, the study of dating based on tree ring patterns. Economic geology, the study of ore genesis, and the mechanisms of ore creation, geochemistry, the applied branch deals with the study of the chemical makeup and behaviour of rocks, and the study of the behaviour of their minerals. Geochronology, the study of isotope geology specifically toward determining the date within the past of rock formation, metamorphism, mineralization and geological events. Geomorphology, the study of landforms and the processes that create them Hydrogeology, igneous petrology, the study of igneous processes such as igneous differentiation, fractional crystallization, intrusive and volcanological phenomena. Isotope geology, the case of the composition of rocks to determine the processes of rock. Metamorphic petrology, the study of the effects of metamorphism on minerals, marine geology, the study of the seafloor, involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal margins. Marine geology has strong ties to physical oceanography and plate tectonics, palaeoclimatology, the application of geological science to determine the climatic conditions present in the Earths atmosphere within the Earths history
Geologist
–
"The Geologist" -
Carl Spitzweg, circa 1860
Geologist
–
Scotsman James Hutton, father of modern geology
Geologist
–
"Geologists at work" from the U.S. Geological and Geographic Survey of the Territories. (1874 - 06/30/1879) Photographer:
William Henry Jackson
Geologist
–
A young geologist learns about
flow banding
19.
Avalanche
–
An avalanche is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a zone from a mechanical failure in the snowpack when the forces on the snow exceed its strength. After initiation, avalanches usually accelerate rapidly and grow in mass, if the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current. Slides of rocks or debris, behaving in a way to snow, are also referred to as avalanches. The remainder of this article refers to snow avalanches, the load on the snowpack may be only due to gravity, in which case failure may result either from weakening in the snowpack or increased load due to precipitation. Avalanches that occur in this way are known as spontaneous avalanches, Avalanches can also be triggered by other loads such as skiers, snowmobilers, animals or explosives. Seismic activity may trigger the failure in the snowpack and avalanches. A popular myth is that avalanches can be triggered by loud noise or shouting, Avalanches are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack. Avalanches are most common during winter or spring but glacier movements may cause ice, there is no universally accepted classification of avalanches—different classifications are useful for different purposes. Avalanches can be described by their size, their potential, their initiation mechanism, their composition. Most avalanches occur spontaneously during storms under increased load due to snowfall, the second largest cause of natural avalanches is metamorphic changes in the snowpack such as melting due to solar radiation. Other natural causes include rain, earthquakes, rockfall and icefall, artificial triggers of avalanches include skiers, snowmobiles, and controlled explosive work. Avalanche initiation can start at a point with only an amount of snow moving initially. A snowpack will fail when the load exceeds the strength, the load is straightforward, it is the weight of the snow. However, the strength of the snowpack is much more difficult to determine and is extremely heterogenous and it varies in detail with properties of the snow grains, size, density, morphology, temperature, water content, and the properties of the bonds between the grains. These properties may all metamorphose in time according to the humidity, water vapour flux, temperature. The top of the snowpack is also influenced by incoming radiation. One of the aims of research is to develop and validate computer models that can describe the evolution of the seasonal snowpack over time
Avalanche
–
The toe of an avalanche in
Alaska 's
Kenai Fjords.
Avalanche
–
A powder snow avalanche in the
Himalayas near
Mount Everest.
Avalanche
–
A crown fracture from a slab avalanche near the Neve Glacier in the
North Cascades mountains. Extensive fracture propagation is evident.
Avalanche
–
Loose snow avalanches (far left) and slab avalanches (near center) near
Mount Shuksan in the
North Cascades mountains. Fracture propagation is relatively limited.
20.
Sediment
–
For sediment in beverages, see dregs. For example, sand and silt can be carried in suspension in water and on reaching the sea be deposited by sedimentation. Sediments are most often transported by water, but also wind, beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of transport and deposition. Glacial moraine deposits and till are ice-transported sediments, sediment can be classified based on its grain size and/or its composition. Sediment size is measured on a log base 2 scale, called the Phi scale, composition of sediment can be measured in terms of, parent rock lithology mineral composition chemical make-up. This leads to an ambiguity in which clay can be used as both a size-range and a composition, sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, rivers and streams carry sediment in their flows. This sediment can be in a variety of locations within the flow and these relationships are shown in the following table for the Rouse number, which is a ratio of sediment fall velocity to upwards velocity. If the upwards velocity is less than the settling velocity, but still high enough for the sediment to move, it will move along the bed as bed load by rolling, sliding. If the upwards velocity is higher than the velocity, the sediment will be transported high in the flow as wash load. As there are generally a range of different particle sizes in the flow, sediment motion can create self-organized structures such as ripples, dunes, antidunes on the river or stream bed. These bedforms are often preserved in rocks and can be used to estimate the direction. Overland flow can erode soil particles and transport them downslope, the erosion associated with overland flow may occur through different methods depending on meteorological and flow conditions. If the initial impact of rain droplets dislodges soil, the phenomenon is called rainsplash erosion, if overland flow is directly responsible for sediment entrainment but does not form gullies, it is called sheet erosion. If the flow and the substrate permit channelization, gullies may form, glaciers carry a wide range of sediment sizes, and deposit it in moraines. The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation and this expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow. This can be localized, and simply due to obstacles, examples are scour holes behind boulders, where flow accelerates
Sediment
–
Cobbles on a beach
Sediment
–
River Rhône flowing into
Lake Geneva
Sediment
–
Sediment billowing out from Italy's shore into the
Adriatic Sea
Sediment
–
Sediment in the
Gulf of Mexico
21.
Continental shelf
–
The continental shelf is an underwater landmass which extends from a continent, resulting in an area of relatively shallow water known as a shelf sea. Much of the shelves were exposed during glacial periods and interglacial periods, the shelf surrounding an island is known as an insular shelf. The continental margin, between the shelf and the abyssal plain, comprises a steep continental slope followed by the flatter continental rise. Sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope, extending as far as 500 km from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rises gradient is intermediate between the slope and the shelf, on the order of 0. 5–1°, the largest shelf – the Siberian Shelf in the Arctic Ocean – stretches to 1,500 kilometers in width. The South China Sea lies over another extensive area of shelf, the Sunda Shelf, which joins Borneo, Sumatra. Other familiar bodies of water that overlie continental shelves are the North Sea, the average width of continental shelves is about 80 km. The depth of the shelf also varies, but is limited to water shallower than 150 m. The slope of the shelf is quite low, on the order of 0. 5°, vertical relief is also minimal. Though the continental shelf is treated as a province of the ocean, it is not part of the deep ocean basin proper. Passive continental margins such as most of the Atlantic coasts have wide and shallow shelves, active continental margins have narrow, relatively steep shelves, due to frequent earthquakes that move sediment to the deep sea. The shelf usually ends at a point of increasing slope, the sea floor below the break is the continental slope. Below the slope is the rise, which finally merges into the deep ocean floor. The continental shelf and the slope are part of the continental margin, the shelf area is commonly subdivided into the inner continental shelf, mid continental shelf, and outer continental shelf, each with their specific geomorphology and marine biology. The character of the shelf changes dramatically at the shelf break, with a few exceptions, the shelf break is located at a remarkably uniform depth of roughly 140 m, this is likely a hallmark of past ice ages, when sea level was lower than it is now. The continental slope is steeper than the shelf, the average angle is 3°. The slope is cut with submarine canyons. The physical mechanisms involved in forming these canyons were not well understood until the 1960s, the continental shelves are covered by terrigenous sediments, that is, those derived from erosion of the continents
Continental shelf
–
Anatomy of a continental shelf of the south eastern coast of the United States
Continental shelf
–
The global continental shelf, highlighted in cyan
Continental shelf
–
Landforms
22.
Oceanic trench
–
The oceanic trenches are linear oceanographic features which are topographic depressions of the sea floor, relatively narrow in width, but hemispheric-scale in length. They are the deepest parts of the ocean floor, a trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to an island arc, and about 200 km from a volcanic arc. Oceanic trenches typically extend 3 to 4 km below the level of the surrounding oceanic floor, the greatest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench, at a depth of 11,034 m below sea level. Oceanic lithosphere moves into trenches at a rate of about 3 km2/yr. Globally, there are over 50 major ocean trenches covering an area of 1.9 million km2 or about 0. 5% of the oceans and this applies to Cascadia, Makran, southern Lesser Antilles, and Calabrian trenches. Trenches are related to but distinguished from continental collision zones, where continental crust enters the subduction zone, when buoyant continental crust enters a trench, subduction eventually stops and the convergent plate margin becomes a collision zone. Trenches were not clearly defined until the late 1940s and 1950s, the bathymetry of the ocean was of no real interest until the late 19th and early 20th centuries, with the initial laying of Transatlantic telegraph cables on the seafloor between the continents. Even then the elongated bathymetric expression of trenches was not recognized until well into the 20th century, the term “trench” does not appear in Murray and Hjort’s classic oceanography book. Instead they applied the term “deep“ for the deepest parts of the ocean, the term was first used in a geologic context by Scofield two years after the war ended to describe a structurally controlled depression in the Rocky Mountains. Johnstone, in his 1923 textbook An Introduction to Oceanography, first used the term in its sense for any marked. His measurements revealed that trenches are sites of downwelling in the solid Earth, the concept of downwelling at trenches was characterized by Griggs in 1939 as the tectogene hypothesis, for which he developed an analogue model using a pair of rotating drums. World War II in the Pacific led to improvements of bathymetry in especially the western and northern Pacific. The rapid growth of deep sea research efforts, especially the use of echosounders in the 1950s and 1960s confirmed the morphological utility of the term. The important trenches were identified, sampled, and their greatest depths sonically plumbed, the heroic phase of trench exploration culminated in the 1960 descent of the Bathyscaphe Trieste, which set an unbeatable world record by diving to the bottom of the Challenger Deep. This has been termed trench rollback or hinge retreat and this is one explanation for the existence of back-arc basins. Slab rollback is a process which occurs during the subduction of two tectonic plates resulting in the motion of the trench. Forces acting perpendicular to the slab at depth are responsible for the migration of the slab in the mantle and ultimately the movement of the hinge
Oceanic trench
–
Major Pacific trenches (1-10) and fracture zones (11-20): 1.
Kermadec 2.
Tonga 3. Bougainville 4.
Mariana 5.
Izu-Ogasawara 6.
Japan 7.
Kuril–Kamchatka 8.
Aleutian 9.
Middle America 10.
Peru-Chile 11. Mendocino 12. Murray 13. Molokai 14. Clarion 15. Clipperton 16. Challenger 17. Eltanin 18. Udintsev 19. East Pacific Rise (S-shaped) 20. Nazca Ridge
Oceanic trench
–
Oceanic crust is formed at an
oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches.
Oceanic trench
–
The
Peru–Chile Trench
Oceanic trench
–
The
Puerto Rico Trench
23.
Shale
–
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable, shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. Mudstones, on the hand, are similar in composition. Before the mid 19th century, the slate, shale. In the context of underground mining, shale was frequently referred to as slate well into the 20th century. Non-fissile rocks of similar composition but made of smaller than 0.06 mm are described as mudstones or claystone. Rocks with similar sizes but with less clay and therefore grittier are siltstones. Shale is the most common sedimentary rock, shales are typically composed of variable amounts of clay minerals and quartz grains and the typical color is gray. Addition of variable amounts of minor constituents alters the color of the rock, black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment. Black shale can also be referred to as black metal, red, brown and green colors are indicative of ferric oxide, iron hydroxide, or micaceous minerals. Clays are the constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite, clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid- to early Paleozoic shales illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and these released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor minerals found in shales and other mudrocks. Shales and mudrocks contain roughly 95 percent of the matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale, black shales, which form in anoxic conditions, contain reduced free carbon along with ferrous iron and sulfur. Pyrite and amorphous iron sulfide along with carbon produce the black coloration, the process in the rock cycle which forms shale is called compaction. The fine particles that compose shale can remain suspended in long after the larger particles of sand have deposited. Shales are typically deposited in very slow moving water and are found in lakes and lagoonal deposits, in river deltas, on floodplains
Shale
–
Shale
Shale
–
Sample of
drill cuttings of shale while drilling an
oil well in
Louisiana,
United States. Sand grain = 2 mm. in dia.
Shale
–
Limey shale overlaid by
limestone,
Cumberland Plateau,
Tennessee
Shale
–
Splitting shale with a large knife to reveal fossils
24.
Limestone
–
Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance, the primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may also form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock, when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls, coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the building process, limestone recrystallizes into marble
Limestone
–
Limestone outcrop in the
Torcal de Antequera nature reserve of
Málaga, Spain
Limestone
–
Limestone quarry at
Cedar Creek, Virginia, USA
Limestone
–
Cutting the limestone blocks at a quarry in
Gozo,
Malta
Limestone
–
Limestone as building material
25.
Wales
–
Wales is a country that is part of the United Kingdom and the island of Great Britain. It is bordered by England to the east, the Irish Sea to the north and west, and it had a population in 2011 of 3,063,456 and has a total area of 20,779 km2. Wales has over 1,680 miles of coastline and is mountainous, with its higher peaks in the north and central areas, including Snowdon. The country lies within the temperate zone and has a changeable. Welsh national identity emerged among the Celtic Britons after the Roman withdrawal from Britain in the 5th century, Llywelyn ap Gruffudds death in 1282 marked the completion of Edward I of Englands conquest of Wales, though Owain Glyndŵr briefly restored independence to Wales in the early 15th century. The whole of Wales was annexed by England and incorporated within the English legal system under the Laws in Wales Acts 1535–1542, distinctive Welsh politics developed in the 19th century. Welsh Liberalism, exemplified in the early 20th century by Lloyd George, was displaced by the growth of socialism, Welsh national feeling grew over the century, Plaid Cymru was formed in 1925 and the Welsh Language Society in 1962. Established under the Government of Wales Act 1998, the National Assembly for Wales holds responsibility for a range of devolved policy matters, two-thirds of the population live in south Wales, mainly in and around Cardiff, Swansea and Newport, and in the nearby valleys. Now that the countrys traditional extractive and heavy industries have gone or are in decline, Wales economy depends on the sector, light and service industries. Wales 2010 gross value added was £45.5 billion, over 560,000 Welsh language speakers live in Wales, and the language is spoken by a majority of the population in parts of the north and west. From the late 19th century onwards, Wales acquired its popular image as the land of song, Rugby union is seen as a symbol of Welsh identity and an expression of national consciousness. The Old English-speaking Anglo-Saxons came to use the term Wælisc when referring to the Celtic Britons in particular, the modern names for some Continental European lands and peoples have a similar etymology. The modern Welsh name for themselves is Cymry, and Cymru is the Welsh name for Wales and these words are descended from the Brythonic word combrogi, meaning fellow-countrymen. The use of the word Cymry as a self-designation derives from the location in the post-Roman Era of the Welsh people in modern Wales as well as in northern England and southern Scotland. It emphasised that the Welsh in modern Wales and in the Hen Ogledd were one people, in particular, the term was not applied to the Cornish or the Breton peoples, who are of similar heritage, culture, and language to the Welsh. The word came into use as a self-description probably before the 7th century and it is attested in a praise poem to Cadwallon ap Cadfan c. 633. Thereafter Cymry prevailed as a reference to the Welsh, until c.1560 the word was spelt Kymry or Cymry, regardless of whether it referred to the people or their homeland. The Latinised forms of names, Cambrian, Cambric and Cambria, survive as lesser-used alternative names for Wales, Welsh
Wales
–
Bryn Celli Ddu, a late Neolithic chambered tomb on Anglesey
Wales
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Flag
Wales
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This article is about the country. For other uses, see
Wales (disambiguation).
Wales
–
Coin of
Magnus Maximus
26.
Scotland
–
Scotland is a country that is part of the United Kingdom and covers the northern third of the island of Great Britain. It shares a border with England to the south, and is surrounded by the Atlantic Ocean, with the North Sea to the east. In addition to the mainland, the country is made up of more than 790 islands, including the Northern Isles, the Kingdom of Scotland emerged as an independent sovereign state in the Early Middle Ages and continued to exist until 1707. By inheritance in 1603, James VI, King of Scots, became King of England and King of Ireland, Scotland subsequently entered into a political union with the Kingdom of England on 1 May 1707 to create the new Kingdom of Great Britain. The union also created a new Parliament of Great Britain, which succeeded both the Parliament of Scotland and the Parliament of England. Within Scotland, the monarchy of the United Kingdom has continued to use a variety of styles, titles, the legal system within Scotland has also remained separate from those of England and Wales and Northern Ireland, Scotland constitutes a distinct jurisdiction in both public and private law. Glasgow, Scotlands largest city, was one of the worlds leading industrial cities. Other major urban areas are Aberdeen and Dundee, Scottish waters consist of a large sector of the North Atlantic and the North Sea, containing the largest oil reserves in the European Union. This has given Aberdeen, the third-largest city in Scotland, the title of Europes oil capital, following a referendum in 1997, a Scottish Parliament was re-established, in the form of a devolved unicameral legislature comprising 129 members, having authority over many areas of domestic policy. Scotland is represented in the UK Parliament by 59 MPs and in the European Parliament by 6 MEPs, Scotland is also a member nation of the British–Irish Council, and the British–Irish Parliamentary Assembly. Scotland comes from Scoti, the Latin name for the Gaels, the Late Latin word Scotia was initially used to refer to Ireland. By the 11th century at the latest, Scotia was being used to refer to Scotland north of the River Forth, alongside Albania or Albany, the use of the words Scots and Scotland to encompass all of what is now Scotland became common in the Late Middle Ages. Repeated glaciations, which covered the land mass of modern Scotland. It is believed the first post-glacial groups of hunter-gatherers arrived in Scotland around 12,800 years ago, the groups of settlers began building the first known permanent houses on Scottish soil around 9,500 years ago, and the first villages around 6,000 years ago. The well-preserved village of Skara Brae on the mainland of Orkney dates from this period and it contains the remains of an early Bronze Age ruler laid out on white quartz pebbles and birch bark. It was also discovered for the first time that early Bronze Age people placed flowers in their graves, in the winter of 1850, a severe storm hit Scotland, causing widespread damage and over 200 deaths. In the Bay of Skaill, the storm stripped the earth from a large irregular knoll, when the storm cleared, local villagers found the outline of a village, consisting of a number of small houses without roofs. William Watt of Skaill, the laird, began an amateur excavation of the site, but after uncovering four houses
Scotland
–
Edinburgh Castle. Human habitation of the site is dated back as far as the 9th century BC, although the nature of this early settlement is unclear.
Scotland
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Flag
Scotland
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The class I
Pictish stone at
Aberlemno known as Aberlemno 1 or the Serpent Stone.
Scotland
–
The
Wallace Monument commemorates
William Wallace, the 13th-century Scottish hero.
27.
Ireland
–
Ireland is an island in the North Atlantic. It is separated from Great Britain to its east by the North Channel, the Irish Sea, Ireland is the second-largest island of the British Isles, the third-largest in Europe, and the twentieth-largest on Earth. Politically, Ireland is divided between the Republic of Ireland, which covers five-sixths of the island, and Northern Ireland, in 2011, the population of Ireland was about 6.4 million, ranking it the second-most populous island in Europe after Great Britain. Just under 4.6 million live in the Republic of Ireland, the islands geography comprises relatively low-lying mountains surrounding a central plain, with several navigable rivers extending inland. The island has lush vegetation, a product of its mild, thick woodlands covered the island until the Middle Ages. As of 2013, the amount of land that is wooded in Ireland is about 11% of the total, there are twenty-six extant mammal species native to Ireland. The Irish climate is moderate and classified as oceanic. As a result, winters are milder than expected for such a northerly area, however, summers are cooler than those in Continental Europe. Rainfall and cloud cover are abundant, the earliest evidence of human presence in Ireland is dated at 10,500 BC. Gaelic Ireland had emerged by the 1st century CE, the island was Christianised from the 5th century onward. Following the Norman invasion in the 12th century, England claimed sovereignty over Ireland, however, English rule did not extend over the whole island until the 16th–17th century Tudor conquest, which led to colonisation by settlers from Britain. In the 1690s, a system of Protestant English rule was designed to materially disadvantage the Catholic majority and Protestant dissenters, with the Acts of Union in 1801, Ireland became a part of the United Kingdom. Northern Ireland saw much civil unrest from the late 1960s until the 1990s and this subsided following a political agreement in 1998. In 1973 the Republic of Ireland joined the European Economic Community while the United Kingdom, Irish culture has had a significant influence on other cultures, especially in the fields of literature. Alongside mainstream Western culture, an indigenous culture exists, as expressed through Gaelic games, Irish music. The culture of the island shares many features with that of Great Britain, including the English language, and sports such as association football, rugby, horse racing. The name Ireland derives from Old Irish Eriu and this in turn derives from Proto-Celtic *Iveriu, which is also the source of Latin Hibernia. Iveriu derives from a root meaning fat, prosperous, during the last glacial period, and up until about 9000 years ago, most of Ireland was covered with ice, most of the time
Ireland
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Satellite image of Ireland on 11 October 2010
Ireland
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The
Gowran Ogham Stone,
Christianised c.6th Century. On display in
St. Mary's Collegiate Church Gowran.
Ireland
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The Uragh Stone Circle a
Neolithic stone circle in Gleninchaquin Park,
County Kerry
28.
Lake District National Park
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The Lake District, also known as the Lakes or Lakeland, is a mountainous region in North West England. A popular holiday destination, it is famous for its lakes, forests and mountains and its associations with the early 19th century writings of William Wordsworth and the other Lake Poets. It is located in the county of Cumbria, and all the land in England higher than 3,000 feet above sea level lies within the National Park, including Scafell Pike, the highest mountain in England. It also contains the deepest and longest bodies of water in England, respectively Wast Water, the Lake District National Park includes nearly all of the Lake District, though the town of Kendal and the Lakeland Peninsulas are currently outside the park boundary. Its aim is to protect the landscape by restricting unwelcome change by industry or commerce, Most of the land in the park is in private ownership, with about 55% registered as agricultural land. Landowners include, Individual farmers and other landowners, with more than half of the agricultural land farmed by the owners. The National Trust owns about a quarter of the total area, the Forestry Commission and other investors in forests and woodland. United Utilities owns 8% Lake District National Park Authority The National Park Authority is based at offices in Kendal and it runs a visitor centre on Windermere at a former country house called Brockhole, Coniston Boating Centre, and Information Centres. Much of the land has statutory open access rights, which cover around 50% of the park. The lakes and mountains combine to form impressive scenery, farmland and settlement have altered the natural scenery, and the ecology has been modified by human influence for millennia and includes important wildlife habitats. However, in 2016 the English Lake District bid for World Heritage Status was submitted to UNESCO in the category of cultural landscape, a decision is expected in 2017. In December 2009, Natural England proposed extending the National Park in the direction of the Yorkshire Dales National Park and this would include land of high landscape value in the Lune Valley. The proposal was opposed by Cumbria County Council who said it would lead to less democratic control, a public inquiry was held into the proposals, which required a decision by the Secretary of State. The decision to recommend approval was announced on October 23,2015, the precise extent of the Lake District was not defined traditionally, but is slightly larger than that of the National Park, the total area of which is about 912 square miles. The park extends just over 32 miles from east to west, the Lake District is one of the most highly populated national parks. There are, however, only a handful of settlements within this mountainous area, the towns of Keswick, Windermere, Ambleside. Villages such as Coniston, Threlkeld, Glenridding, Pooley Bridge, Broughton-in-Furness, Grasmere, Newby Bridge, Staveley, Lindale, Gosforth, the economies of almost all are intimately linked with tourism. Beyond these are a scattering of hamlets and many isolated farmsteads, some of which are tied to agriculture
Lake District National Park
–
The
Skiddaw massif, town of
Keswick and
Derwent Water seen from
Walla Crag
Lake District National Park
–
The A591 road as it passes through the countryside between Ambleside and Grasmere
Lake District National Park
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A panorama from the summit of Scafell Pike, August 2007
Lake District National Park
–
Panorama of the Wasdale screes descending into Wastwater, the deepest lake in England.
29.
England
–
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west, the Irish Sea lies northwest of England and the Celtic Sea lies to the southwest. England is separated from continental Europe by the North Sea to the east, the country covers five-eighths of the island of Great Britain in its centre and south, and includes over 100 smaller islands such as the Isles of Scilly, and the Isle of Wight. England became a state in the 10th century, and since the Age of Discovery. The Industrial Revolution began in 18th-century England, transforming its society into the worlds first industrialised nation, Englands terrain mostly comprises low hills and plains, especially in central and southern England. However, there are uplands in the north and in the southwest, the capital is London, which is the largest metropolitan area in both the United Kingdom and the European Union. In 1801, Great Britain was united with the Kingdom of Ireland through another Act of Union to become the United Kingdom of Great Britain and Ireland. In 1922 the Irish Free State seceded from the United Kingdom, leading to the latter being renamed the United Kingdom of Great Britain, the name England is derived from the Old English name Englaland, which means land of the Angles. The Angles were one of the Germanic tribes that settled in Great Britain during the Early Middle Ages, the Angles came from the Angeln peninsula in the Bay of Kiel area of the Baltic Sea. The earliest recorded use of the term, as Engla londe, is in the ninth century translation into Old English of Bedes Ecclesiastical History of the English People. According to the Oxford English Dictionary, its spelling was first used in 1538. The earliest attested reference to the Angles occurs in the 1st-century work by Tacitus, Germania, the etymology of the tribal name itself is disputed by scholars, it has been suggested that it derives from the shape of the Angeln peninsula, an angular shape. An alternative name for England is Albion, the name Albion originally referred to the entire island of Great Britain. The nominally earliest record of the name appears in the Aristotelian Corpus, specifically the 4th century BC De Mundo, in it are two very large islands called Britannia, these are Albion and Ierne. But modern scholarly consensus ascribes De Mundo not to Aristotle but to Pseudo-Aristotle, the word Albion or insula Albionum has two possible origins. Albion is now applied to England in a poetic capacity. Another romantic name for England is Loegria, related to the Welsh word for England, Lloegr, the earliest known evidence of human presence in the area now known as England was that of Homo antecessor, dating to approximately 780,000 years ago. The oldest proto-human bones discovered in England date from 500,000 years ago, Modern humans are known to have inhabited the area during the Upper Paleolithic period, though permanent settlements were only established within the last 6,000 years
England
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Stonehenge, a
Neolithic monument
England
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Flag
England
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Boudica led an uprising against the
Roman Empire
England
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Replica of a 7th-century ceremonial
helmet from the
Kingdom of East Anglia, found at
Sutton Hoo
30.
New Zealand
–
New Zealand /njuːˈziːlənd/ is an island nation in the southwestern Pacific Ocean. The country geographically comprises two main landmasses—the North Island, or Te Ika-a-Māui, and the South Island, or Te Waipounamu—and around 600 smaller islands. New Zealand is situated some 1,500 kilometres east of Australia across the Tasman Sea and roughly 1,000 kilometres south of the Pacific island areas of New Caledonia, Fiji, because of its remoteness, it was one of the last lands to be settled by humans. During its long period of isolation, New Zealand developed a distinct biodiversity of animal, fungal, the countrys varied topography and its sharp mountain peaks, such as the Southern Alps, owe much to the tectonic uplift of land and volcanic eruptions. New Zealands capital city is Wellington, while its most populous city is Auckland, sometime between 1250 and 1300 CE, Polynesians settled in the islands that later were named New Zealand and developed a distinctive Māori culture. In 1642, Dutch explorer Abel Tasman became the first European to sight New Zealand, in 1840, representatives of Britain and Māori chiefs signed the Treaty of Waitangi, which declared British sovereignty over the islands. In 1841, New Zealand became a colony within the British Empire, today, the majority of New Zealands population of 4.7 million is of European descent, the indigenous Māori are the largest minority, followed by Asians and Pacific Islanders. Reflecting this, New Zealands culture is derived from Māori and early British settlers. The official languages are English, Māori and New Zealand Sign Language, New Zealand is a developed country and ranks highly in international comparisons of national performance, such as health, education, economic freedom and quality of life. Since the 1980s, New Zealand has transformed from an agrarian, Queen Elizabeth II is the countrys head of state and is represented by a governor-general. In addition, New Zealand is organised into 11 regional councils and 67 territorial authorities for local government purposes, the Realm of New Zealand also includes Tokelau, the Cook Islands and Niue, and the Ross Dependency, which is New Zealands territorial claim in Antarctica. New Zealand is a member of the United Nations, Commonwealth of Nations, ANZUS, Organisation for Economic Co-operation and Development, Pacific Islands Forum, and Asia-Pacific Economic Cooperation. Dutch explorer Abel Tasman sighted New Zealand in 1642 and called it Staten Landt, in 1645, Dutch cartographers renamed the land Nova Zeelandia after the Dutch province of Zeeland. British explorer James Cook subsequently anglicised the name to New Zealand, Aotearoa is the current Māori name for New Zealand. It is unknown whether Māori had a name for the country before the arrival of Europeans. Māori had several names for the two main islands, including Te Ika-a-Māui for the North Island and Te Waipounamu or Te Waka o Aoraki for the South Island. Early European maps labelled the islands North, Middle and South, in 1830, maps began to use North and South to distinguish the two largest islands and by 1907, this was the accepted norm. The New Zealand Geographic Board discovered in 2009 that the names of the North Island and South Island had never been formalised and this set the names as North Island or Te Ika-a-Māui, and South Island or Te Waipounamu
New Zealand
–
The Waitangi sheet from the
Treaty of Waitangi
New Zealand
–
Flag
New Zealand
–
Painting of
Mount Earnslaw by John Turnbull Thomson, oil on canvas, 1888
New Zealand
–
John Key,
Prime Minister of New Zealand since 2008
31.
Mineral
–
A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids, the study of minerals is called mineralogy. There are over 5,300 known mineral species, over 5,070 of these have been approved by the International Mineralogical Association, the silicate minerals compose over 90% of the Earths crust. The diversity and abundance of species is controlled by the Earths chemistry. Silicon and oxygen constitute approximately 75% of the Earths crust, which translates directly into the predominance of silicate minerals, minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Minerals can be described by their various properties, which are related to their chemical structure. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, more specific tests for describing minerals include magnetism, taste or smell, radioactivity and reaction to acid. Minerals are classified by key chemical constituents, the two dominant systems are the Dana classification and the Strunz classification, the silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a unit of a 4− silica tetrahedron—that is, a silicon cation coordinated by four oxygen anions. These tetrahedra can be polymerized to give the subclasses, orthosilicates, disilicates, cyclosilicates, inosilicates, phyllosilicates, other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates. The first criterion means that a mineral has to form by a natural process, stability at room temperature, in the simplest sense, is synonymous to the mineral being solid. More specifically, a compound has to be stable or metastable at 25 °C, modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula, many mineral groups and species are composed of a solid solution, pure substances are not usually found because of contamination or chemical substitution. Finally, the requirement of an ordered atomic arrangement is usually synonymous with crystallinity, however, crystals are also periodic, an ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form, hardness, and cleavage. There have been recent proposals to amend the definition to consider biogenic or amorphous substances as minerals. The formal definition of an approved by the IMA in 1995, A mineral is an element or chemical compound that is normally crystalline. However, if geological processes were involved in the genesis of the compound, Mineral classification schemes and their definitions are evolving to match recent advances in mineral science
Mineral
–
Amethyst, a variety of
quartz
Mineral
–
Schist is a
metamorphic rock characterized by an abundance of platy minerals. In this example, the rock has prominent
sillimanite porphyroblasts as large as 3 cm (1.2 in).
Mineral
–
Hübnerite, the manganese-rich end-member of the
wolframite series, with minor quartz in the background
Mineral
–
When minerals react, the products will sometimes assume the shape of the reagent; the product mineral is termed to be a pseudomorph of (or after) the reagent. Illustrated here is a pseudomorph of
kaolinite after
orthoclase. Here, the pseudomorph preserved the Carlsbad
twinning common in orthoclase.
32.
Orthoclase
–
Orthoclase, or orthoclase feldspar, is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for straight fracture, because its two planes are at right angles to each other. It is a type of potassium feldspar, also known as K-feldspar, the gem known as moonstone is largely composed of orthoclase. Orthoclase is a constituent of most granites and other felsic igneous rocks and often forms huge crystals. Typically, the pure potassium endmember of orthoclase forms a solution with albite. While slowly cooling within the earth, sodium-rich albite lamellae form by exsolution, the resulting intergrowth of the two feldspars is called perthite. The higher-temperature polymorph of KAlSi3O8 is sanidine, sanidine is common in rapidly cooled volcanic rocks such as obsidian and felsic pyroclastic rocks, and is notably found in trachytes of the Drachenfels, Germany. The lower-temperature polymorph of KAlSi3O8 is microcline, adularia is a low temperature form of either microcline or orthoclase originally reported from the low temperature hydrothermal deposits in the Adula Alps of Switzerland. It was first described by Ermenegildo Pini in 1781, the optical effect of adularescence in moonstone is typically due to adularia. The largest documented crystal of orthoclase was found in Ural mountains. It measured ~10×10×0.4 m and weighed ~100 tons, together with the other potassium feldspars, orthoclase is a common raw material for the manufacture of some glasses and some ceramics such as porcelain, and as a constituent of scouring powder. Some intergrowths of orthoclase and albite have an attractive pale luster and are called moonstone when used in jewellery, most moonstones are translucent and white, although grey and peach-colored varieties also occur. In gemology, their luster is called adularescence and is described as creamy or silvery white with a billowy quality. It is the gem of Florida. Orthoclase is one of the ten defining minerals of the Mohs scale of mineral hardness, nASAs Curiosity Rover discovery of high levels of orthoclase in Martian sandstones suggested that some Martian rocks may have experienced complex geological processing, such as repeated melting
Orthoclase
–
Orthoclase
Orthoclase
–
Adularia with
pyrite incrustations.
33.
Plagioclase
–
Plagioclase is a series of tectosilicate minerals within the feldspar group. Rather than referring to a mineral with a specific chemical composition, plagioclase is a continuous solid solution series. This was first shown by the German mineralogist Johann Friedrich Christian Hessel in 1826, the series ranges from albite to anorthite endmembers, where sodium and calcium atoms can substitute for each other in the minerals crystal lattice structure. Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or record-groove effect, plagioclase is a major constituent mineral in the Earths crust, and is consequently an important diagnostic tool in petrology for identifying the composition, origin and evolution of igneous rocks. Plagioclase is also a constituent of rock in the highlands of the Earths moon. Analysis of thermal emission spectra from the surface of Mars suggests that plagioclase is the most abundant mineral in the crust of Mars, the extinction angle is an optical characteristic and varies with the albite fraction. There are several named plagioclase feldspars that fall between albite and anorthite in the series, the following table shows their compositions in terms of constituent anorthite and albite percentages. Anorthite was named by Gustav Rose in 1823 from the Ancient Greek meaning oblique, anorthite is a comparatively rare mineral but occurs in the basic plutonic rocks of some orogenic calc-alkaline suites. Albite is named from the Latin albus, in reference to its pure white color. It is a common and important rock-making mineral associated with the more acid rock types and in pegmatite dikes, often with rarer minerals like tourmaline. The intermediate members of the group are very similar to each other. Bytownite, named after the name for Ottawa, Canada, is a rare mineral occasionally found in more basic rocks. Labradorite is the characteristic feldspar of the basic rock types such as diorite, gabbro, andesite. Labradorite frequently shows an iridescent display of colors due to light refracting within the lamellae of the crystal and it is named after Labrador, where it is a constituent of the intrusive igneous rock anorthosite which is composed almost entirely of plagioclase. A variety of known as spectrolite is found in Finland. Andesine is a mineral of rocks such as diorite which contain a moderate amount of silica. Oligoclase is common in granite, syenite, diorite, and gneiss and it is a frequent associate of orthoclase. The name oligoclase is derived from the Greek for little and fracture, sunstone is mainly oligoclase with flakes of hematite
Plagioclase
–
A
photomicrograph of a plagioclase
crystal under cross
polarized light. The plagioclase crystal shows a distinct banding effect called
polysynthetic twinning.
Plagioclase
–
Plagioclase displaying
cleavage. (unknown scale)
Plagioclase
–
In
volcanic rocks,
fine-grained plagioclase can display a 'microlitic' texture of many small
crystals.
Plagioclase
–
Anorthite
34.
Calcite
–
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The Mohs scale of hardness, based on scratch hardness comparison. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite, aragonite will change to calcite at 380–470 °C, and vaterite is even less stable. Calcite is derived from the German Calcit, a term coined in the 19th century from the Latin word for lime and it is thus etymologically related to chalk. Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals, however, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms and it may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form and its fracture is conchoidal, but difficult to obtain. It has a defining Mohs hardness of 3, a gravity of 2.71. Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A transparent variety called Iceland spar is used for optical purposes, acute scalenohedral crystals are sometimes referred to as dogtooth spar while the rhombohedral form is sometimes referred to as nailhead spar. Single calcite crystals display an optical property called birefringence and this strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect was first described by the Danish scientist Rasmus Bartholin in 1669, at a wavelength of ~590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively. Between 190 and 1700 nm, the refractive index varies roughly between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4. Calcite, like most carbonates, will dissolve with most forms of acid, calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Although calcite is fairly insoluble in water, acidity can cause dissolution of calcite. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite, calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. On a landscape scale, continued dissolution of calcium carbonate-rich rocks can lead to the expansion and eventual collapse of cave systems, high-grade optical calcite was used in World War II for gun sights, specifically in bomb sights and anti-aircraft weaponry
Calcite
–
A one-inch calcite
rhomb that shows the
double image refraction property
Calcite
–
Crystal structure of calcite
Calcite
–
faceted calcite, oval cut, 1.12ct, Mexico.
Calcite
–
Doubly terminated calcite crystal.
35.
Iron oxide
–
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides, common rust is a form of iron oxide. Iron oxides are used as inexpensive, durable pigments in paints, coatings. Colors commonly available are in the end of the yellow/orange/red/brown/black range. When used as a coloring, it has E number E172. Limonite Iron oxide nanoparticles List of inorganic pigments Information from Nano-Oxides, http, //chemed. chem. purdue. edu/demos/demosheets/12.3. html http, //minerals. usgs. gov/minerals/pubs/commodity/iron_oxide/ CDC - NIOSH Pocket Guide to Chemical Hazards de
Iron oxide
–
Iron oxide pigment
36.
Felsite
–
Felsite is a very fine grained volcanic rock that may or may not contain larger crystals. Felsite is a term for a light colored rock that typically requires petrographic examination or chemical analysis for more precise definition. Color is generally white through light gray, or red to tan and may include any color except dark gray and this rock is typically of extrusive origin, formed by compaction of fine volcanic ash, and may be found in association with obsidian and rhyolite. In some cases, it is sufficiently fine-grained for use in making stone tools and its fine texture and felsic components allow for good knapped pieces, much like working chert, producing conchoidal fracture. Dendritic manganese oxides such as pyrolusite and/or iron oxides such as limonite may precipitate along rock crevices, giving some rock chunk surfaces multicolored or arborescent patterned textures
Felsite
–
Felsite covered with
dendritic pyrolusite formations.
Felsite
–
Volcano types
37.
Chert
–
Chert is a fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline silica. Depending on its origin, it can contain either microfossils, small macrofossils, Chert occurs as oval to irregular nodules in greensand, limestone, chalk, and dolostone formations as a replacement mineral, where it is formed as a result of some type of diagenesis. Where it occurs in chalk or marl, it is usually called flint and it also occurs in thin beds, when it is a primary deposit. Thick beds of chert occur in marine deposits. These thickly bedded cherts include the novaculite of the Ouachita Mountains of Arkansas, Oklahoma, the banded iron formations of Precambrian age are composed of alternating layers of chert and iron oxides. Chert also occurs in deposits and is known as diatomaceous chert. Diatomaceous chert consists of beds and lenses of diatomite which were converted during diagenesis into dense, in petrology the term chert is used to refer generally to all rocks composed primarily of microcrystalline, cryptocrystalline and microfibrous quartz. The term does not include quartzite, chalcedony is a microfibrous variety of quartz. Strictly speaking, the flint is reserved for varieties of chert which occur in chalk. Among non-geologists, the distinction between flint and chert is often one of quality - chert being lower quality than flint, among petrologists, chalcedony is sometimes considered separately from chert due to its fibrous structure. Since many cherts contain both microcrystalline and microfibrous quartz, it is difficult to classify a rock as completely chalcedony. The cryptocrystalline nature of chert, combined with its above average ability to resist weathering, recrystallization, for example, The 3.2 Ga chert of the Fig Tree Formation in the Barbeton Mountains between Swaziland and South Africa preserved non-colonial unicellular bacteria-like fossils. The Gunflint Chert of western Ontario preserves not only bacteria and cyanobacteria but also believed to be ammonia-consuming and some that resemble green algae. The Apex Chert of the Pilbara craton, Australia preserved eleven taxa of prokaryotes, the Bitter Springs Formation of the Amadeus Basin, Central Australia, preserves 850 Ma cyanobacteria and algae. The Rhynie chert of Scotland has remains of a Devonian land flora, in prehistoric times, chert was often used as a raw material for the construction of stone tools. Like obsidian, as well as some rhyolites, felsites, quartzites and this results in conchoidal fractures, a characteristic of all minerals with no cleavage planes. When a chert stone is struck against an iron-bearing surface sparks result and this makes chert an excellent tool for starting fires, and both flint and common chert were used in various types of fire-starting tools, such as tinderboxes, throughout history. Cherts are subject to problems when used as concrete aggregates, deeply weathered chert develops surface pop-outs when used in concrete that undergoes freezing and thawing because of the high porosity of weathered chert
Chert
–
Chert
Chert
–
A chert nodule from the
Onondaga limestone layer,
Buffalo, New York. (3.8 cm wide)
Chert
–
Chert (dark bands) in the
Devonian Corriganville-New Creek limestone,
Everett, Pennsylvania
Chert
38.
Slate
–
Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock, foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression. The foliation in slate is called slaty cleavage and it is caused by strong compression causing fine grained clay flakes to regrow in planes perpendicular to the compression. Slate is frequently grey in color, especially when seen, en masse, Slate is not to be confused with shale, from which it may be formed, or schist. The word slate is used for certain types of object made from slate rock. It may mean a single roofing tile made of slate, or a writing slate and this was traditionally a small smooth piece of the rock, often framed in wood, used with chalk as a notepad or noticeboard, and especially for recording charges in pubs and inns. The phrases clean slate and blank slate come from this usage, before the mid-19th century, the terms slate, shale and schist were not sharply distinguished. In the context of underground mining in the United States. For example, roof slate referred to shale above a coal seam, occasionally, as in the purple slates of North Wales, ferrous reduction spheres form around iron nuclei, leaving a light green spotted texture. These spheres are sometimes deformed by a subsequent applied stress field to ovoids, Slate can be made into roofing slates, a type of roof shingle, or more specifically a type of roof tile, which are installed by a slater. Slate has two lines of breakability – cleavage and grain – which make it possible to split the stone into thin sheets, when broken, slate retains a natural appearance while remaining relatively flat and easy to stack. Slate is particularly suitable as a material as it has an extremely low water absorption index of less than 0. 4%. In fact, this natural slate, which requires only minimal processing, has the lowest embodied energy of all roofing materials, natural slate is used by building professionals as a result of its beauty and durability. Slate is incredibly durable and can last several hundred years, often little or no maintenance. Its low water makes it very resistant to frost damage and breakage due to freezing. Natural slate is also fire resistant and energy efficient, Slate roof tiles are usually fixed either with nails, or with hooks as is common with Spanish slate. In the UK, fixing is typically with double nails onto timber battens or nailed directly onto timber sarking boards, nails were traditionally of copper, although there are modern alloy and stainless steel alternatives. Both these methods, if used properly, provide a long-lasting weathertight roof with a lifespan of around 80–100 years, Slate roofs are still used today
Slate
–
Slate
Slate
–
Slate Macro (~ 6 cm long and ~ 4 cm high)
Slate
–
Slate roof
Slate
–
Mules carrying slate roof tiles.
Dharamsala, India. 1993
39.
Gneiss
–
Gneiss is a common distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks. The foliations are characterized by alternating darker and lighter colored bands, the word gneiss comes from the Middle High German verb gneist. It has occurred in English since at least 1757, gneissic rocks are usually medium- to coarse-foliated, they are largely recrystallized but do not carry large quantities of micas, chlorite or other platy minerals. Gneisses that are metamorphosed igneous rocks or their equivalent are termed granite gneisses, diorite gneisses, gneiss rocks may also be named after a characteristic component such as garnet gneiss, biotite gneiss, albite gneiss, etc. Orthogneiss designates a gneiss derived from a rock, and paragneiss is one from a sedimentary rock. Gneissose rocks have properties similar to gneiss, gneiss appears to be striped in bands, called gneissic banding. The banding is developed under high temperature and pressure conditions, the minerals are arranged into layers that appear as bands in cross section. The appearance of layers, called compositional banding, occurs because the layers, the darker bands have relatively more mafic minerals. The lighter bands contain relatively more felsic and these forces stretch out the rock like a plastic, and the original material is spread out into sheets. Another cause of banding is metamorphic differentiation, which separates different materials into different layers through chemical reactions, not all gneiss rocks have detectable banding. In kyanite gneiss, crystals of kyanite appear as random clumps in what is mainly a plagioclase matrix, henderson gneiss is found in North Carolina and South Carolina, US, east of the Brevard Shear Zone. It has deformed into two sequential forms, the second, more warped, form is associated with the Brevard Fault, and the first deformation results from displacement to the southwest. Most of the Outer Hebrides of Scotland have a formed from Lewisian gneiss. In addition to the Outer Hebrides, they form basement deposits on the Scottish mainland west of the Moine Thrust and on the islands of Coll and Tiree. These rocks are igneous in origin, mixed with metamorphosed marble, quartzite and mica schist with later intrusions of basaltic dikes. Gneisses of Archean and Proterozoic age occur in the Baltic Shield, in antiquity, gneisses were also utilized in architectural construction. They were used to erect the Sphinx of Taharqo in the Nile Valley, list of rock types Blatt, Harvey and Robert J. Tracy. Petrology, Igneous, Sedimentary and Metamorphic, 2nd ed. Freeman, mcKirdy, Alan, Roger Crofts and John Gordon
Gneiss
–
Sample of gneiss exhibiting "gneissic banding".
Gneiss
–
Granitic gneiss from Enfield, New York
Gneiss
–
Orthogneiss from the Czech Republic
Gneiss
–
Henderson augen gneiss
40.
Schist
–
Schist is a medium-grade metamorphic rock with medium to large, flat, sheet-like grains in a preferred orientation. It is defined by having more than 50% platy and elongated minerals, often finely interleaved with quartz and these lamellar minerals include micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a form called quartz schist is produced. Schist forms at a temperature and has larger grains than phyllite. Geological foliation with medium to large grained flakes in a preferred orientation is called schistosity. The names of various schists are derived from their mineral constituents, for example, schists rich in mica are called mica schists and include biotite or muscovite. Most schists are mica schists, but graphite and chlorite schists are also common, Schists are also named for their prominent or perhaps unusual mineral constituents, as in the case of garnet schist, tourmaline schist, and glaucophane schist. The individual mineral grains in schist, drawn out into flaky scales by heat and pressure, Schist is characteristically foliated, meaning that the individual mineral grains split off easily into flakes or slabs. Most schists are derived from clays and muds that have passed through a series of processes involving the production of shales, slates and phyllites as intermediate steps. Certain schists are derived from fine-grained igneous rocks such as basalts, before the mid-18th century, the terms slate, shale and schist were not sharply differentiated by those involved with mining. In the context of underground mining, shale was frequently referred to as slate well into the 20th century. During metamorphism, rocks which were originally sedimentary, igneous or metamorphic are converted into schists, if the composition of the rocks was originally similar, they may be very difficult to distinguish from one another if the metamorphism has been great. A quartz-porphyry, for example, and a fine grained feldspathic sandstone, usually, however, it is possible to distinguish between sedimentary and igneous schists and gneisses. If, for example, the district occupied by these rocks has traces of bedding, clastic structure, or unconformability. In other cases intrusive junctions, chilled edges, contact alteration or porphyritic structure may prove that in its original condition a metamorphic gneiss was an igneous rock. Such rocks as limestones, dolomites, quartzites and aluminous shales have very definite chemical characteristics which distinguish them even when completely recrystallized, the schists are classified principally according to the minerals they consist of and on their chemical composition. For example, many metamorphic limestones, marbles, and calc-schists, with crystalline dolomites, contain silicate minerals such as mica, tremolite, diopside, scapolite, quartz and they are derived from calcareous sediments of different degrees of purity. Another group is rich in quartz, with amounts of white and black mica, garnet, feldspar, zoisite
Schist
–
Schist specimen showing the characteristic "scaly" schistose texture, caused by platy micas
Schist
–
Microscopic view of garnet-mica-schist in
thin section under polarized light with a large garnet crystal (black) in a matrix of quartz and feldspar (white and gray grains) and parallel strands of mica (red, purple and brown).
Schist
–
View of cut garnet-mica-schist
Schist
–
Manhattan schist from southeastern New York State
41.
Quartzite
–
Quartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. Sandstone is converted into quartzite through heating and pressure related to tectonic compression within orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in shades of pink. Other colors, such as yellow, green, blue and orange, are due to other minerals, when sandstone is cemented to quartzite, the individual quartz grains recrystallize along with the former cementing material to form an interlocking mosaic of quartz crystals. Most or all of the texture and sedimentary structures of the sandstone are erased by the metamorphism. The grainy, sandpaper-like surface becomes glassy in appearance, minor amounts of former cementing materials, iron oxide, silica, carbonate and clay, often migrate during recrystallization and metamorphosis. This causes streaks and lenses to form within the quartzite, orthoquartzite is a very pure quartz sandstone composed of usually well-rounded quartz grains cemented by silica. Orthoquartzite is often 99% SiO2 with only minor amounts of iron oxide and trace resistant minerals such as zircon, rutile. Although few fossils are present, the original texture and sedimentary structures are preserved. The term is traditionally used for quartz-cemented quartz arenites. Quartzite is very resistant to weathering and often forms ridges. The nearly pure silica content of the rock provides little for soil, therefore, because of its hardness and angular shape, crushed quartzite is often used as railway ballast. Quartzite is a stone and may be used to cover walls, as roofing tiles, as flooring. Its use for countertops in kitchens is expanding rapidly and it is harder and more resistant to stains than granite. Crushed quartzite is used in road construction. High purity quartzite is used to produce ferrosilicon, industrial silica sand, during the Paleolithic quartzite was used, in addition to flint, quartz, and other lithic raw materials, for making stone tools. Quartzite is also found in the Morenci Copper Mine in Arizona, the town of Quartzsite in western Arizona derives its name from the quartzites in the nearby mountains in both Arizona and Southeastern California. A glassy vitreous quartzite has been described from the Belt Supergroup in the Coeur d’Alene district of northern Idaho, in the United Kingdom, a craggy ridge of quartzite called the Stiperstones runs parallel with the Pontesford-Linley fault,6 km north-west of the Long Mynd in south Shropshire
Quartzite
–
Blue Quartzite from
Maurienne valley in the
French Alps
Quartzite
–
Quartzite has a grainy, sandpaper-like surface which becomes glassy in appearance
Quartzite
–
Abandoned quartzite mine in
Kakwa Provincial Park, British Columbia, Canada
Quartzite
–
Quartzite biface
hand axe from
Stellenbosch, South Africa
42.
Biotite
–
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K 3AlSi 3O102. Hausmann in 1847 in honor of the French physicist Jean-Baptiste Biot, iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. It is sometimes called iron mica because it is more iron-rich than phlogopite and it is also sometimes called black mica as opposed to white mica – both form in some rocks, and in some instances side-by-side. Like other mica minerals, biotite has a perfect basal cleavage, and consists of flexible sheets, or lamellae. It has a crystal system, with tabular to prismatic crystals with an obvious pinacoid termination. It has four faces and two pinacoid faces to form a pseudohexagonal crystal. Although not easily seen because of the cleavage and sheets, fracture is uneven and it appears greenish to brown or black, and even yellow when weathered. It can be transparent to opaque, has a vitreous to pearly luster, when biotite is found in large chunks, they are called “books” because it resembles a book with pages of many sheets. The color of biotite is usually black and the mineral has a hardness of 2. 5-3 on the Mohs scale of mineral hardness, biotite dissolves in both acid and alkaline aqueous solutions, with the highest dissolution rates at low pH. However, biotite dissolution is highly anisotropic with crystal edge surfaces reacting 45 to 132 times faster than basal surfaces, under cross-polarized light biotite can generally be identified by the gnarled birds eye extinction. Biotite is found in a variety of igneous and metamorphic rocks. For instance, biotite occurs in the lava of Mount Vesuvius, biotite in granite tends to be poorer in magnesium than the biotite found in its volcanic equivalent, rhyolite. Biotite is an essential phenocryst in some varieties of lamprophyre, biotite is occasionally found in large cleavable crystals, especially in pegmatite veins, as in New England, Virginia and North Carolina. Other notable occurrences include Bancroft and Sudbury, Ontario and it is an essential constituent of many metamorphic schists, and it forms in suitable compositions over a wide range of pressure and temperature. It has been estimated that biotite comprises up to 7% of the continental crust. The largest documented single crystals of biotite were approximately 7 m2 sheets found in Iveland, biotite is used extensively to constrain ages of rocks, by either potassium-argon dating or argon-argon dating. Because argon escapes readily from the crystal structure at high temperatures. Biotite is also useful in assessing temperature histories of metamorphic rocks, because the partitioning of iron and magnesium between biotite and garnet is sensitive to temperature
Biotite
–
Thin tabular biotite aggregate (Image width: 2.5 mm)
43.
Chlorite group
–
The chlorites are a group of phyllosilicate minerals. Chlorites can be described by the following four endmembers based on their chemistry via substitution of the four elements in the silicate lattice, Mg, Fe, Ni. Clinochlore, O108 Chamosite, O108 Nimite, O108 Pennantite, 64O108 In addition, zinc, lithium, the great range in composition results in considerable variation in physical, optical, and X-ray properties. Similarly, the range of chemical composition allows chlorite group minerals to exist over a range of temperature and pressure conditions. For this reason chlorite minerals are ubiquitous minerals within low and medium temperature metamorphic rocks, some rocks, hydrothermal rocks. The name chlorite is from the Greek chloros, meaning green, the typical general formula is, 34O102·36. This formula emphasizes the structure of the group, chlorites have a 2,1 sandwich structure, this is often referred to as a talc layer. Unlike other 2,1 clay minerals, a chlorites interlayer space is composed of 6 and this 6 unit is more commonly referred to as the brucite-like layer, due to its closer resemblance to the mineral brucite. Therefore, chlorites structure appears as follows, -t-o-t-brucite-t-o-t-brucite, thats why they are also called 2,1,1 minerals. An older classification divided the chlorites into two subgroups, the orthochlorites and leptochlorites, the terms are seldom used and the ortho prefix is somewhat misleading as the chlorite crystal system is monoclinic and not orthorhombic. Chlorite is commonly found in rocks as an alteration product of mafic minerals such as pyroxene, amphibole. Chlorite is a common mineral associated with ore deposits and commonly occurs with epidote, sericite, adularia. Chlorite is also a metamorphic mineral, usually indicative of low-grade metamorphism. It is the species of the zeolite facies and of lower greenschist facies. It occurs in the quartz, albite, sericite, chlorite, within ultramafic rocks, metamorphism can also produce predominantly clinochlore chlorite in association with talc. Chlorite occurs naturally in a variety of locations and forms, for example, chlorite is found naturally in certain parts of Wales in mineral schists. Chlorite is found in large boulders scattered on the surface on Ring Mountain in Marin County. Clinoclore, pennantite, and chamosite are the most common varieties, several other sub-varieties have been described
Chlorite group
–
Chlorite group
Chlorite group
–
Quartz crystal with chlorite inclusions from
Minas Gerais,
Brazil (size: 4.2 × 3.9 × 3.3 cm)
Chlorite group
–
Chlorite
pseudomorph after
garnet from Michigan (size: 3.5 × 3.1 × 2.7 cm)
Chlorite group
–
Chlorite schist
44.
Tourmaline
–
Tourmaline is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a stone and the gemstone comes in a wide variety of colors. The name comes from the Tamil and Sinhalese word Turmali or Thoramalli, brightly colored Sri Lankan gem tourmalines were brought to Europe in great quantities by the Dutch East India Company to satisfy a demand for curiosities and gems. At the time it was not realised that schorl and tourmaline were the same mineral, tourmaline was sometimes called the Ceylonese Magnet because it could attract and then repel hot ashes due to its pyroelectric properties. Tourmalines were used by chemists in the 19th century to light by shining rays onto a cut. It may account for 95% or more of all tourmaline in nature, the early history of the mineral schorl shows that the name schorl was in use prior to 1400 because a village known today as Zschorlau was then named Schorl. This village had a tin mine where, in addition to cassiterite. The first description of schorl with the name schürl and its occurrence was written by Johannes Mathesius in 1562 under the title Sarepta oder Bergpostill, up to about 1600, additional names used in the German language were Schurel, Schörle, and Schurl. Beginning in the 18th century, the name Schörl was mainly used in the German-speaking area, in English, the names shorl and shirl were used in the 18th century. In the 19th century the names common schorl, schörl, schorl, dravite, also called brown tourmaline, is the sodium magnesium rich tourmaline endmember. Uvite, in comparison, is a calcium magnesium tourmaline, dravite forms multiple series, with other tourmaline members, including schorl and elbaite. Today this tourmaline locality at Dravograd, is a part of the Republic of Slovenia, tschermak gave this tourmaline the name dravite, for the Drava river area, which is the district along the Drava River in Austria and Slovenia. Dravite varieties include the green chromium dravite and the vanadium dravite. A lithium-tourmaline elbaite was one of three pegmatitic minerals from Utö, Sweden, in which the new alkali element lithium was determined in 1818 by Johan August Arfwedson for the first time. Elba Island, Italy, was one of the first localities where colored, in 1850 Karl Friedrich August Rammelsberg described fluorine in tourmaline for the first time. In 1870 he proved that all varieties of tourmaline contain chemically bound water, in 1889 Scharitzer proposed the substitution of by F in red Li-tourmaline from Sušice, Czech Republic. In 1914 Vladimir Vernadsky proposed the name Elbait for lithium-, sodium-, most likely the type material for elbaite was found at Fonte del Prete, San Piero in Campo, Campo nellElba, Elba Island, Province of Livorno, Tuscany, Italy. In 1933 Winchell published a formula for elbaite, H8Na2Li3Al3B6Al12Si12O62
Tourmaline
–
Schorl Tourmaline
Tourmaline
–
Rubellite, 1.63ct, Brazil
Tourmaline
–
Indicolite, 1.45ct, Brazil
Tourmaline
–
Bi-Color Tourmaline, 6.75ct, Brazil
45.
Epidote
–
Epidote is a calcium aluminium iron sorosilicate mineral. The faces are often deeply striated and crystals are often twinned, many of the characters of the mineral vary with the amount of iron present for instance, the color, the optical constants, and the specific gravity. The color is green, grey, brown or nearly black and it displays strong pleochroism, the pleochroic colors being usually green, yellow and brown. Clinozoisite is green, white or pale rose-red group species containing very little iron, the name, due to Haüy, is derived from the Greek word epidosis which means addition in allusion to one side of the ideal prism being longer than the other. Epidote is an abundant rock-forming mineral, but one of secondary origin and it occurs in marble and schistose rocks of metamorphic origin. It is also a product of alteration of various minerals composing igneous rocks. A rock composed of quartz and epidote is known as epidosite, the perfectly transparent, dark green crystals from the Knappenwand and from Brazil have occasionally been cut as gemstones. Belonging to the same group with epidote are the species piemontite and allanite. Piemontite occurs as small, reddish-black, monoclinic crystals in the mines at San Marcel, near Ivrea in Piedmont. The purple color of the Egyptian porfido rosso antico is due to the presence of this mineral, allanite and dollaseite- have the same general epidote formula and contain metals of the cerium group. The crystallographic and optical characters are similar to those of epidote, the pleochroism is strong with reddish-, yellowish-, and greenish-brown colors. Although not a mineral, allanite is of fairly wide distribution as a primary accessory constituent of many crystalline rocks, gneiss, granite, syenite, rhyolite, andesite. It was first found in the granite of east Greenland and described by Thomas Allan in 1808, allanite is a mineral readily altered by hydration, becoming optically isotropic and amorphous, for this reason several varieties have been distinguished, and many different names applied. Orthite was the name given by Jöns Berzelius in 1818 to a form found as slender prismatic crystals, sometimes a foot in length, at Finbo. Dollaseite is less common, famous from the Ostanmossa mine in the Norberg district of Sweden, dallasite This article incorporates text from a publication now in the public domain, Chisholm, Hugh, ed. article name needed
Epidote
–
Epidote crystals – Deposit topotype
Epidote
–
Epidote from
Alaska
Epidote
–
Sample of dollaseite (dark brown matrix at arrow points) from Sweden
46.
Apatite
–
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the four most common endmembers is written as Ca1062, apatite is a mineral that is often mistaken for other minerals. This tendency is reflected in the name, which is derived from the Greek word απατείν. Apatite is one of a few minerals produced and used by biological micro-environmental systems, apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the component of tooth enamel. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate, fluoridated water allows exchange in the teeth of fluoride ions for hydroxyl groups in apatite. Similarly, toothpaste typically contains a source of fluoride anions, too much fluoride results in dental fluorosis and/or skeletal fluorosis. Fission tracks in apatite are commonly used to determine the history of orogenic belts. /He dating of apatite is also established for use in determining thermal histories and other. Phosphorite is a sedimentary rock, that contains between 18% and 40% P2O5. The apatite in phosphorite is present as cryptocrystalline masses referred to as collophane, the primary use of apatite is in the manufacture of fertilizer – it is a source of phosphorus. It is occasionally used as a gemstone, green and blue varieties, in finely divided form, are pigments with excellent covering power. During digestion of apatite with sulfuric acid to phosphoric acid. This byproduct is an industrial source of hydrofluoric acid. Fluoro-chloro apatite forms the basis of the now obsolete Halophosphor fluorescent tube phosphor system and this system has been almost entirely replaced by the Tri-Phosphor system. In the United States, apatite-derived fertilizers are used to supplement the nutrition of many agricultural crops by providing a source of phosphate. Apatites are also a proposed host material for storage of nuclear waste, apatite is infrequently used as a gemstone. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon-cut, chatoyant stones are known as cats-eye apatite, transparent green stones are known as asparagus stone, and blue stones have been called moroxite
Apatite
–
Apatite group
Apatite
–
Apatity, Russia, a site of apatite mines and processing facilities
Apatite
–
Faceted blue apatite, Brasil
Apatite
–
Apatite Crystal, Mexico
47.
Garnet
–
Garnets are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, the different species are pyrope, almandine, spessartine, grossular, uvarovite and andradite. The garnets make up two solid solution series, pyrope-almandine-spessartine and uvarovite-grossular-andradite, the word garnet comes from the 14th‑century Middle English word gernet, meaning dark red. It is derived from the Latin granatus, from granum, Garnet species are found in many colors including red, orange, yellow, green, purple, brown, blue, black, pink, and colorless, with reddish shades most common. Garnet species light transmission properties can range from the gemstone-quality transparent specimens to the varieties used for industrial purposes as abrasives. The minerals luster is categorized as vitreous or resinous, garnets are nesosilicates having the general formula X3Y23. The X site is occupied by divalent cations 2+ and the Y site by trivalent cations 3+ in an octahedral/tetrahedral framework with 4− occupying the tetrahedra. Garnets are most often found in the crystal habit, but are also commonly found in the trapezohedron habit. They crystallize in the system, having three axes that are all of equal length and perpendicular to each other. Garnets do not show cleavage, so when they fracture under stress, because the chemical composition of garnet varies, the atomic bonds in some species are stronger than in others. As a result, this group shows a range of hardness on the Mohs scale of about 6.5 to 7.5. The harder species like almandine are often used for abrasive purposes, for gem identification purposes, a pick-up response to a strong neodymium magnet separates garnet from all other natural transparent gemstones commonly used in the jewelry trade. Almandine, Fe3Al23 Pyrope, Mg3Al23 Spessartine, Mn3Al23 Almandine, sometimes incorrectly called almandite, is the modern gem known as carbuncle, the term carbuncle is derived from the Latin meaning live coal or burning charcoal. The name Almandine is a corruption of Alabanda, a region in Asia Minor where these stones were cut in ancient times, chemically, almandine is an iron-aluminium garnet with the formula Fe3Al23, the deep red transparent stones are often called precious garnet and are used as gemstones. Almandine occurs in metamorphic rocks like mica schists, associated with such as staurolite, kyanite, andalusite. Almandine has nicknames of Oriental garnet, almandine ruby, and carbuncle, Pyrope is red in color and chemically an aluminium silicate with the formula Mg3Al23, though the magnesium can be replaced in part by calcium and ferrous iron. The color of pyrope varies from red to black. A variety of pyrope from Macon County, North Carolina is a shade and has been called rhodolite
Garnet
–
Garnet
Garnet
–
A sample showing the deep red color garnet can exhibit.
Garnet
–
Crystal structure model of garnet
Garnet
–
Almandine in metamorphic rock
48.
Hornblende
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Hornblende is a complex inosilicate series of minerals. It is not a mineral in its own right, but the name is used as a general or field term. Hornblende is a mixture of three molecules, a calcium-iron-magnesium silicate, an aluminium-iron-magnesium silicate, and an iron-magnesium silicate. The general formula can be given as 2–358O222, some metals vary in their occurrence and magnitude, Manganese and titanium are often present. Sodium and potassium are present and fluorine often substitutes for the hydroxyl in the crystalline structure. Hornblende has a hardness of 5–6, a gravity of 2. 9–3.4 and is typically an opaque green. Its cleavage angles are at 56 and 124 degrees and it is most often confused with various pyroxene minerals and biotite mica, which are black and can be found in granite and in charnockite. Hornblende is a constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro, basalt, andesite, gneiss. It is the mineral of amphibolites. Very dark brown to black hornblendes that contain titanium are ordinarily called basaltic hornblende, from the fact that they are usually a constituent of basalt, hornblende alters easily to chlorite and epidote. A rare variety of hornblende contains less than 5% of iron oxide, is gray to white in color, and named edenite, from its locality in Edenville, Orange County, New York. List of minerals Hurlbut, Cornelius S. Klein, Cornelis,1985, Manual of Mineralogy, 20th ed. John Wiley and Sons, New York, p 416-7, ISBN 0-471-80580-7 Scandinavian mineral gallery retrieved 06/21/05
Hornblende
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Amphibole Hornblende
49.
Augite
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Augite is a common rock-forming pyroxene mineral with formula 2O6. The crystals are monoclinic and prismatic, augite has two prominent cleavages, meeting at angles near 90 degrees. Augite is a solution in the pyroxene group. Diopside and hedenbergite are important endmembers in augite, but augite can also contain significant aluminium, titanium, with declining temperature, augite may exsolve lamellae of pigeonite and/or orthopyroxene. There is also a miscibility gap between augite and omphacite, but this gap occurs at higher temperatures, there are no industrial or economic uses for this mineral. Augite is a mineral in mafic igneous rocks, for example, gabbro and basalt. It also occurs in relatively high-temperature metamorphic rocks such as mafic granulite and it commonly occurs in association with orthoclase, sanidine, labradorite, olivine, leucite, amphiboles and other pyroxenes. Occasional specimens have an appearance that give rise to the minerals name. It was named by Abraham Gottlob Werner in 1792, transparent augites containing dendritic patterns are used as gems and ornamental stones known as shajar in parts of India. It is found near the Ken River, local jewelers export raw shajar stone and items to different parts of India. Banda is one city noted for trade of shazar stone, fassaite Deer, W. A. Howie, R. A. and Zussman, J. An introduction to the rock-forming minerals
Augite
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Augite -
Muhavura volcano
Augite
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Euhedral crystal of augite from
Teide (4.4 x 3.0 x 2.3 cm)
50.
Sphene
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Titanite, or sphene, is a calcium titanium nesosilicate mineral, CaTiSiO5. Trace impurities of iron and aluminium are typically present, also commonly present are rare earth metals including cerium and yttrium, calcium may be partly replaced by thorium. Sphene was the most commonly used name until the IMA decision, the name sphene continues to be publishable in peer-reviewed scientific literature, e. g. a paper by Hayden et al. was published in early 2008 in the journal Contributions to Mineralogy and Petrology. Sphene persists as the name for titanite gemstones. Titanite, which is named for its content, occurs as translucent to transparent, reddish brown, gray, yellow, green. These crystals are typically sphenoid in habit and are often twinned, possessing a subadamantine tending to slightly resinous luster, titanite has a hardness of 5.5 and a weak cleavage. Its specific gravity varies between 3.52 and 3.54, transparent specimens are noted for their strong trichroism, the three colours presented being dependent on body colour. Owing to the effect of iron, sphene exhibits no fluorescence under ultraviolet light. Some titanite has been found to be metamict, in consequence of damage due to radioactive decomposition of the often significant thorium content. When viewed in section with a petrographic microscope, pleochroic halos can be observed in minerals surrounding a titanite crystal. Titanite occurs as an accessory mineral in intermediate and felsic igneous rocks. It also occurs in rocks such as gneiss and schists. Titanite is a source of titanium dioxide, TiO2, used in pigments, as a gemstone, titanite is usually some shade of chartreuse, but can be brown or black. Hue depends on Fe content, with low Fe content causing green and yellow colours and it is prized for its exceptional dispersive power which exceeds that of diamond. Jewelry use of titanite is limited, both because the stone is uncommon in gem quality and is relatively soft, titanite can also be used as a U-Pb geochronometer, specifically in metamorphic terranes
Sphene
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Titanite crystals on amphibole (image width 2 mm)
Sphene
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Green titanite crystal cluster from the Tormiq Valley, Haramosh Mountains, Pakistan
This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Greywacke". Encyclopædia Britannica (11th ed.). Cambridge University Press.
