A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earths volcanoes occur because its crust is broken into 17 major, therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. This type of volcanism falls under the umbrella of plate hypothesis volcanism, Volcanism away from plate boundaries has been explained as mantle plumes. These so-called hotspots, for example Hawaii, are postulated to arise from upwelling diapirs with magma from the boundary,3,000 km deep in the Earth. Volcanoes are usually not created where two plates slide past one another. Erupting volcanoes can pose hazards, not only in the immediate vicinity of the eruption. Historically, so-called volcanic winters have caused catastrophic famines, the word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology.
The study of volcanoes is called volcanology, sometimes spelled vulcanology, at the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. Most divergent plate boundaries are at the bottom of the oceans, most volcanic activity is submarine, black smokers are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the temperature of the overlying mantle wedge. This magma tends to be very viscous due to its high content, so it often does not reach the surface. When it does reach the surface, a volcano is formed, typical examples of this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire.
Because tectonic plates move across them, each volcano becomes dormant and is eventually re-formed as the plate advances over the postulated plume and this theory is currently under criticism, however. The most common perception of a volcano is of a mountain, spewing lava and poisonous gases from a crater at its summit, however. The features of volcanoes are more complicated and their structure. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have features such as massive plateaus
Natrocarbonatite is a rare carbonatite lava which erupts from the Ol Doinyo Lengai volcano in Tanzania within the East African Rift of eastern Africa. Whereas most lavas are rich in minerals, the natrocarbonatite lavas of Ol Doinyo Lengai are rich in the rare sodium and potassium carbonate minerals. Due to this composition, the lava is erupted at relatively low temperatures. This temperature is so low that the molten lava appears black in sunlight and it is much more fluid than silicate lavas. The black or dark brown lava and ash erupted begins to turn white within a few hours, the resulting volcanic landscape is different from any other in the world
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula Na2Al2Si3O10 · 2H2O, the type locality is Hohentwiel, Germany. It was named natrolite by Martin Heinrich Klaproth in 1803, the name is derived from νατρών natron, the Greek word for soda, in reference to the sodium content and λίθος lithos, meaning stone. Needle stone or needle-zeolite are other names, alluding to the common acicular habit of the crystals. The crystals are frequently epitaxial overgrowths of natrolite, larger crystals most commonly have the form of a square prism terminated by a low pyramid, the prism angle being nearly a right angle. The crystals are tetragonal in appearance, though actually orthorhombic, there are perfect cleavages parallel to the faces of the prism. The mineral occurs in compact fibrous aggregates, the fibers having a divergent or radial arrangement. Natrolite is readily distinguished from other fibrous zeolites by its optical characteristics, between crossed nicols the fibers extinguish parallel to their length, and they do not show an optic figure in convergent polarized light.
Natrolite is usually white or colorless, but sometimes reddish or yellowish, the luster is vitreous, or, in finely fibrous specimens, silky. The specific gravity is 2.2, and the hardness is 5.5, the mineral is readily fusible, melting in a candle-flame to which it imparts a yellow color owing to the presence of sodium. It is decomposed by hydrochloric acid with separation of gelatinous silica, natrolite occurs with other zeolites in the amygdaloidal cavities of basaltic igneous rocks. It is common in nepheline syenites, excellent specimens of diverging groups of white prismatic crystals are found in compact basalt at the Puy-deMarman, Puy-de-Dôme, France. Huge crystals have found on the Kola Peninsula, Russia. Mont St. Hilaire, Quebec has produced large crystals associated with many rare minerals, the Bay of Fundy in Nova Scotia, New Jersey and British Columbia have produced excellent specimens. Several varieties of natrolite have been distinguished by special names, fargite is a red natrolite from Glenfarg in Perthshire.
Bergmannite, or Spreustein, is a variety which has resulted by the alteration of other minerals, chiefly sodalite. Structure type NAT Mineral Galleries Mindat Webmineral This article incorporates text from a now in the public domain, Hugh
History of Earth
The history of Earth concerns the development of the planet Earth from its formation to the present day. Nearly all branches of science have contributed to the understanding of the main events of the Earths past. The age of Earth is approximately one-third of the age of the universe, an immense amount of geological change has occurred in that timespan, accompanied by the emergence of life and its subsequent evolution. Earth formed around 4.54 billion years ago by accretion from the solar nebula, volcanic outgassing probably created the primordial atmosphere and the ocean, but the atmosphere contained almost no oxygen and so would have been toxic to most modern life including humans. Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. A giant impact collision with a body named Theia while Earth was in its earliest stage. Over time, the Earth cooled, causing the formation of a solid crust, the geological time scale clock depicts the larger spans of time from the beginning of the Earth as well as a chronology of some definitive events of Earth history.
The Archean and Proterozoic eons follow, they produced the abiogenesis of life on Earth, there are microbial mat fossils such as stromatolites found in 3.48 billion-year-old sandstone discovered in Western Australia. According to one of the researchers, If life arose relatively quickly on Earth … it could be common in the universe, living forms derived from photosynthesis appeared between 3.2 and 2.4 billion years ago and began enriching the atmosphere with oxygen. More than 99 percent of all species, amounting to five billion species. Estimates on the number of Earths current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described. Geological change has been a constant of Earths crust since the time of its formation, species continue to evolve, taking on new forms, splitting into daughter species or going extinct in the process of adapting or dying in response to ever-changing physical environments.
The process of plate tectonics continues to play a dominant role in the shaping of Earths oceans and continents, in geochronology, time is generally measured in mya, each unit representing the period of approximately 1,000,000 years in the past. The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet, each eon saw the most significant changes in Earths composition and life. Each eon is divided into eras, which in turn are divided into periods. The history of the Earth can be organized according to the geologic time scale. The following four timelines show the time scale
Sodalite is a rich royal blue tectosilicate mineral widely used as an ornamental gemstone. Although massive sodalite samples are opaque, crystals are transparent to translucent. Sodalite is a member of the group with hauyne, nosean. A light, relatively hard yet fragile mineral, sodalite is named after its sodium content, well known for its blue color, sodalite may be grey, green, or pink and is often mottled with white veins or patches. The more uniformly blue material is used in jewellery, where it is fashioned into cabochons, lesser material is more often seen as facing or inlay in various applications. Although somewhat similar to lazurite and lapis lazuli, sodalite rarely contains pyrite and it is further distinguished from similar minerals by its white streak. Sodalites six directions of cleavage may be seen as incipient cracks running through the stone. It is sometimes referred to as poor mans lapis due to its similar color and its name comes from its high sodium content. Most sodalite will fluoresce orange under ultraviolet light, and hackmanite exhibits tenebrescence, hackmanite is an important variety of sodalite exhibiting tenebrescence.
When hackmanite from Mont Saint-Hilaire or Ilímaussaq is freshly quarried, it is pale to deep violet. Conversely, hackmanite from Afghanistan and the Myanmar Republic starts off creamy white, if left in a dark environment for some time, the violet will fade again. Tenebrescence is accelerated by the use of longwave or, much sodalite will fluoresce a patchy orange under UV light. Sodalite was first described in 1811 for the occurrence in its locality in the Ilimaussaq complex, Narsaq. Occurring typically in massive form, sodalite is found as fillings in plutonic igneous rocks such as nepheline syenites. It is associated with other minerals typical of undersaturated environments, namely leucite and natrolite, other associated minerals include nepheline, titanian andradite, microcline, albite, fluorite and baryte. Significant deposits of material are restricted to but a few locales, Bancroft and Mont-Saint-Hilaire, Quebec, in Canada, and Litchfield, Maine. The Ice River complex, near Golden, British Columbia, contains sodalite, smaller deposits are found in South America, Romania and Russia.
Hackmanite is found principally in Mont-Saint-Hilaire and Greenland, transparent crystals are found in northern Namibia and in the lavas of Vesuvius, Italy
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, lustre, colour, tenacity, fracture, more specific tests for describing minerals include magnetism, taste or smell 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, disilicates, inosilicates, other important mineral groups include the native elements, oxides, carbonates 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 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, crystals are periodic, an ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form 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
Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a rock, is a combination of the minerals quartz, feldspar. The Earths outer solid layer, the lithosphere, is made of rock, rock has been used by mankind throughout history. The minerals and metals found in rocks have been essential to human civilization, three major groups of rocks are defined, igneous and metamorphic. The scientific study of rocks is called petrology, which is a component of geology. At a granular level, rocks are composed of grains of minerals, the aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed, many rocks contain silica, a compound of silicon and oxygen that forms 74. 3% of the Earths crust. This material forms crystals with other compounds in the rock, the proportion of silica in rocks and minerals is a major factor in determining their name and properties.
Rocks are geologically classified according to such as mineral and chemical composition, the texture of the constituent particles. These physical properties are the end result of the processes that formed the rocks, over the course of time, rocks can transform from one type into another, as described by the geological model called the rock cycle. These events produce three general classes of rock, igneous and metamorphic, the three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks, hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series. Igneous rock forms through the cooling and solidification of magma or lava and this magma can be derived from partial melts of pre-existing rocks in either a planets mantle or crust. Typically, the melting of rocks is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, igneous rocks are divided into two main categories, plutonic rock and volcanic.
Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earths crust, a common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta, the chemical abundance and the rate of cooling of magma typically forms a sequence known as Bowens reaction series. Most major igneous rocks are found along this scale, about 64. 7% of the Earths crust by volume consists of igneous rocks, making it the most plentiful category. Of these, 66% are basalts and gabbros, 16% are granite, only 0. 6% are syenites and 0. 3% peridotites and dunites
Baryte or barite is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine and anhydrite, baryte is generally white or colorless, and is the main source of barium. Baryte and celestine form a solid solution SO4, the radiating form, sometimes referred to as Bologna Stone, attained some notoriety among alchemists for the phosphorescent specimens found in the 17th century near Bologna by Vincenzo Casciarolo. In practice, this is usually the mineral baryte, most crude baryte requires some upgrading to minimum purity or density. Baryte that is used as an aggregate in a heavy cement is crushed and screened to a uniform size, the name baryte is derived from the Greek word βαρύς. Other names have been used for baryte, including barytine, schwerspath, Heavy Spar, baryte occurs in a large number of depositional environments, and is deposited through a large number of processes including biogenic and evaporation, among others. Baryte commonly occurs in veins in limestones, in hot spring deposits.
It is often associated with the minerals anglesite and celestine and it has been identified in meteorites. It is mined in Arkansas, Virginia, North Carolina, Tennessee, Nevada, world baryte production for 2014 was 9.7 million tonnes. The major baryte producers are as follows, India, United States, Iran and Kazakhstan. The main users of baryte in 2014 were US, Gulf States, 77% of baryte worldwide is used as a weighting agent for drilling fluids in oil and gas exploration to suppress high formation pressures and prevent blowouts. As a well is drilled, the bit passes through various formations, the deeper the hole, the more baryte is needed as a percentage of the total mud mix. Baryte used for drilling petroleum wells can be black, brown or gray depending on the ore body. The baryte is finely ground so that at least 97% of the material, by weight, can pass through a 200-mesh screen, in August 2010 API published specifications to modify the 4.2 drilling grade standards for baryte to include 4.1 SG materials.
It is used to other barium chemicals, notably barium carbonate which is used for the manufacture of LED glass for television and computer screens. Historically baryte was used for the production of barium hydroxide for sugar refining, and as a pigment for textiles, paper. Although baryte contains a metal, it is not a toxic chemical because of its extreme insolubility. It is used as gemstone
Brazil, officially the Federative Republic of Brazil, is the largest country in both South America and Latin America. As the worlds fifth-largest country by area and population, it is the largest country to have Portuguese as an official language. Its Amazon River basin includes a vast tropical forest, home to wildlife, a variety of ecological systems. This unique environmental heritage makes Brazil one of 17 megadiverse countries, Brazil was inhabited by numerous tribal nations prior to the landing in 1500 of explorer Pedro Álvares Cabral, who claimed the area for the Portuguese Empire. Brazil remained a Portuguese colony until 1808, when the capital of the empire was transferred from Lisbon to Rio de Janeiro, in 1815, the colony was elevated to the rank of kingdom upon the formation of the United Kingdom of Portugal and the Algarves. Independence was achieved in 1822 with the creation of the Empire of Brazil, a state governed under a constitutional monarchy. The ratification of the first constitution in 1824 led to the formation of a bicameral legislature, the country became a presidential republic in 1889 following a military coup détat.
An authoritarian military junta came to power in 1964 and ruled until 1985, Brazils current constitution, formulated in 1988, defines it as a democratic federal republic. The federation is composed of the union of the Federal District, the 26 states, Brazils economy is the worlds ninth-largest by nominal GDP and seventh-largest by GDP as of 2015. A member of the BRICS group, Brazil until 2010 had one of the worlds fastest growing economies, with its economic reforms giving the country new international recognition. Brazils national development bank plays an important role for the economic growth. Brazil is a member of the United Nations, the G20, BRICS, Mercosul, Organization of American States, Organization of Ibero-American States, CPLP. Brazil is a power in Latin America and a middle power in international affairs. One of the worlds major breadbaskets, Brazil has been the largest producer of coffee for the last 150 years and it is likely that the word Brazil comes from the Portuguese word for brazilwood, a tree that once grew plentifully along the Brazilian coast.
In Portuguese, brazilwood is called pau-brasil, with the word brasil commonly given the etymology red like an ember, formed from Latin brasa and the suffix -il. As brazilwood produces a red dye, it was highly valued by the European cloth industry and was the earliest commercially exploited product from Brazil. The popular appellation eclipsed and eventually supplanted the official Portuguese name, early sailors sometimes called it the Land of Parrots. In the Guarani language, a language of Paraguay, Brazil is called Pindorama
Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally CaMg2. The term is used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name used for the dolomitic rock type is dolostone. Most probably the mineral dolomite was first described by Carl Linnaeus in 1768, nicolas-Théodore de Saussure first named the mineral in March 1792. The mineral dolomite crystallizes in the trigonal-rhombohedral system and it forms white, gray, or pink crystals. Dolomite is a carbonate, having an alternating structural arrangement of calcium and magnesium ions. It does not rapidly dissolve or effervesce in dilute hydrochloric acid as calcite does, solid solution exists between dolomite, the iron-dominant ankerite and the manganese-dominant kutnohorite. Small amounts of iron in the give the crystals a yellow to brown tint. Manganese substitutes in the structure up to three percent MnO. A high manganese content gives the crystals a rosy pink color, lead and cobalt substitute in the structure for magnesium.
The mineral dolomite is closely related to huntite Mg3Ca4, because dolomite can be dissolved by slightly acidic water, areas of dolomite are important as aquifers and contribute to karst terrain formation. Modern dolomite formation has been found to occur under conditions in supersaturated saline lagoons along the Rio de Janeiro coast of Brazil, Lagoa Vermelha. It is often thought that dolomite will develop only with the help of sulfate-reducing bacteria, low-temperature dolomite may occur in natural environments rich in organic matter and microbial cell surfaces. This occurs as a result of magnesium complexation by carboxyl groups associated with organic matter, vast deposits of dolomite are present in the geological record, but the mineral is relatively rare in modern environments. Reproducible, inorganic low-temperature syntheses of dolomite and magnesite were published for the first time in 1999, the general principle governing the course of this irreversible geochemical reaction has been coined breaking Ostwalds step rule.
There is some evidence for an occurrence of dolomite. One example is that of the formation of dolomite in the bladder of a Dalmatian dog. In 2015, it was discovered that the direct crystallization of dolomite can occur from solution at temperatures between 60 and 220 °C
Scandium and yttrium are considered rare earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties. They are not especially rare, but they tend to occur together in nature and are difficult to separate from one another, because of their geochemical properties, rare earth elements are typically dispersed and not often found concentrated as rare earth minerals in economically exploitable ore deposits. The first such mineral discovered was gadolinite, a composed of cerium, iron, silicon. This mineral was extracted from a mine in the village of Ytterby in Sweden, a table listing the seventeen rare earth elements, their atomic number and symbol, the etymology of their names, and their main usages is provided here. The distinction between the groups is more to do with atomic volume and geological behavior, Rare earth elements became known to the world with the discovery of the black mineral Ytterbite by Lieutenant Carl Axel Arrhenius in 1787, at a quarry in the village of Ytterby, Sweden.
Arrheniuss ytterbite reached Johan Gadolin, a Royal Academy of Turku professor, anders Gustav Ekeberg isolated beryllium from the gadolinite but failed to recognize other elements that the ore contained. After this discovery in 1794 a mineral from Bastnäs near Riddarhyttan, Sweden, in 1803 they obtained a white oxide and called it ceria. Martin Heinrich Klaproth independently discovered the same oxide and called it ochroia, in 1839 Carl Gustav Mosander, an assistant of Berzelius, separated ceria by heating the nitrate and dissolving the product in nitric acid. He called the oxide of the soluble salt lanthana and it took him three more years to separate the lanthana further into didymia and pure lanthana. Didymia, although not further separable by Mosanders techniques, was a mixture of oxides, in 1842 Mosander separated the yttria into three oxides, pure yttria and erbia. The earth giving pink salts he called terbium, the one that yielded yellow peroxide he called erbium, so in 1842 the number of known rare earth elements had reached six, cerium, didymium and terbium.
This confusion led to false claims of new elements, such as the mosandrium of J. Lawrence Smith. There were no further discoveries for 30 years, and the element didymium was listed in the table of elements with a molecular mass of 138. In 1879 Delafontaine used the new process of optical-flame spectroscopy. Also in 1879, the new element samarium was isolated by Paul Émile Lecoq de Boisbaudran from the mineral samarskite, the samaria earth was further separated by Lecoq de Boisbaudran in 1886 and a similar result was obtained by Jean Charles Galissard de Marignac by direct isolation from samarskite. They named the element gadolinium after Johan Gadolin, and its oxide was named gadolinia, the fractional crystallization of the oxides yielded europium in 1901. In 1839 the third source for rare earths became available and this is a mineral similar to gadolinite, uranotantalum. This mineral from Miass in the southern Ural Mountains was documented by Gustave Rose, the exact number of rare earth elements that existed was highly unclear, and a maximum number of 25 was estimated
Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava, the magma can be derived from partial melts of existing rocks in either a planets mantle or crust. Typically, the melting is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks and metamorphic rocks make up 90–95% of the top 16 km of the Earths crust by volume. Igneous rocks form about 15% of the Earths current land surface, most of the Earths oceanic crust is made of igneous rock. In terms of modes of occurrence, igneous rocks can be either intrusive or extrusive, the mineral grains in such rocks can generally be identified with the naked eye.
Intrusive rocks can be classified according to the shape and size of the intrusive body, typical intrusive formations are batholiths, laccoliths and dikes. When the magma solidifies within the earths crust, it cools slowly forming coarse textured rocks, such as granite, the central cores of major mountain ranges consist of intrusive igneous rocks, usually granite. When exposed by erosion, these cores may occupy huge areas of the Earths surface, intrusive igneous rocks that form at depth within the crust are termed plutonic rocks and are usually coarse-grained. Intrusive igneous rocks that form near the surface are termed subvolcanic or hypabyssal rocks, hypabyssal rocks are less common than plutonic or volcanic rocks and often form dikes, laccoliths, lopoliths, or phacoliths. Extrusive igneous rocks, known as rocks, are formed at the crusts surface as a result of the partial melting of rocks within the mantle. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks and they are formed by the cooling of molten magma on the earths surface.
The magma, which is brought to the surface through fissures or volcanic eruptions, hence such rocks are smooth and fine-grained. Basalt is an extrusive igneous rock and forms lava flows, lava sheets. Some kinds of basalt solidify to form long polygonal columns, the Giants Causeway in Antrim, Northern Ireland is an example. The molten rock, with or without suspended crystals and gas bubbles, is called magma and it rises because it is less dense than the rock from which it was created. When magma reaches the surface from beneath water or air, it is called lava, eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine. Black smokers and mid-ocean ridge basalt are examples of volcanic activity