Christian Leopold von Buch
His scientific interest was devoted to a broad spectrum of geological topics, fossils and more. His most remembered accomplishment is the definition of the Jurassic system. He was known as Leopold von Buch, Buch studied with Alexander von Humboldt under Abraham Gottlob Werner at the mining school in Freiberg, Saxony. He afterwards completed his education at the universities of Halle and Göttingen and he began writing on geological topics early in life. His Versuch einer mineralogischen Beschreibung von Landeck was translated into French, in 1802 he published Entwurf einer geognostischen Beschreibung von Schlesien, which became the first volume of his Geognostische Beobachtungen auf Reisen durch Deutschland und Italien. He was at time a zealous upholder of the Neptunian theory of Werner. In 1797, he met Humboldt at Salzburg, and with him explored the geological formations of Styria, in the spring of 1798, Buch extended his excursions into Italy, where his faith in the Neptunian theory was shaken.
In his early works, he had advocated the aqueous origin of basaltic and other formations, but now he saw cause to abandon Werners theory and he saw Vesuvius for the first time in 1799. Later, in 1805, he had the opportunity, along with Humboldt and Gay Lussac and it was a remarkable eruption, and supplied Buch with data for refuting many erroneous ideas entertained regarding volcanoes. In 1802 he examined the extinct volcanoes of the Auvergne in the south of France. The aspect of the Puy de Dôme, with its cone of trachyte and its strata of basaltic lava, the results of all these geological travels were given to the world in the two volumes of his Geognostische Beobachtungen. In 1806, Buch proceeded to Scandinavia and spent two years in examining its physical constitution and this furnished the materials for his work entitled Reise durch Norwegen und Lappland. He made many important observations on the geography of plants, on climatology and he showed that many of the erratic blocks on the North German plains must have come from Scandinavia.
He established the fact that the whole of Sweden is slowly but continuously rising above the level of the sea from Frederikshald to Abo, in 1815 Buch visited the Canary Islands in company with Christen Smith, a Norwegian botanist. These volcanic isles furnished the starting point from which Buch commenced a course of study on the production. This is attested by his work on the subject entitled Physical Description of the Canary Isles. During his time in the Canary Islands, he visited the Las Cañadas Caldera on Tenerife, when he published his memoirs and observations about his excursion, he introduced the Spanish word Caldera into the geological and scientific vocabulary. After his return from the Canaries he visited the group of the Hebrides
Metamorphism
Metamorphism is the change of minerals or geologic texture in pre-existing rocks, without the protolith melting into liquid magma. The change occurs primarily due to heat and the introduction of chemically active fluids, the chemical components and crystal structures of the minerals making up the rock may change even though the rock remains a solid. Changes at or just beneath Earths surface due to weathering and/or diagenesis are not classified as metamorphism, Metamorphism typically occurs between diagenesis, and melting. Three types of metamorphism exist, contact and regional, Metamorphism produced with increasing pressure and temperature conditions is known as prograde metamorphism. Conversely, decreasing temperatures and pressure characterize retrograde metamorphism, Metamorphic rocks can change without melting. When pressure is applied, somewhat flattened grains that orient in the same direction have a stable configuration. The upper boundary of metamorphic conditions is related to the onset of melting processes in the rock, the maximum temperature for metamorphism is typically 700 –900 °C, depending on the pressure and on the composition of the rock.
Migmatites are rocks formed at this limit, which contain pods. Since the 1980s it has recognized that rocks are rarely dry enough. Conditions producing widespread regionally metamorphosed rocks occur during an orogenic event, the collision of two continental plates or island arcs with continental plates produce the extreme compressional forces required for the metamorphic changes typical of regional metamorphism. These orogenic mountains are eroded, exposing the intensely deformed rocks typical of their cores. The conditions within the slab as it plunges toward the mantle in a subduction zone produce regional metamorphic effects. The techniques of structural geology are used to unravel the collisional history, regional metamorphism can be described and classified into metamorphic facies or metamorphic zones of temperature/pressure conditions throughout the orogenic terrane. Contact metamorphism occurs typically around intrusive igneous rocks as a result of the increase caused by the intrusion of magma into cooler country rock.
The area surrounding the intrusion where the contact metamorphism effects are present is called the metamorphic aureole, contact metamorphic rocks are usually known as hornfels. Rocks formed by contact metamorphism may not present signs of deformation and are often fine-grained. Contact metamorphism is greater adjacent to the intrusion and dissipates with distance from the contact, the size of the aureole depends on the heat of the intrusion, its size, and the temperature difference with the wall rocks. Dikes generally have small aureoles with minimal metamorphism whereas large ultramafic intrusions can have significantly thick, the metamorphic grade of an aureole is measured by the peak metamorphic mineral which forms in the aureole
Pegmatite
A pegmatite is a holocrystalline, intrusive igneous rock composed of interlocking phaneritic crystals usually larger than 2.5 cm in size, such rocks are referred to as pegmatitic. The word pegmatite derives from Homeric Greek, πεγνυμι, which means “to bind together”, in reference to the crystals of quartz. Most pegmatites are composed of quartz and mica, having a similar composition as granite. Crystal size is the most striking feature of pegmatites, with usually over 5 cm in size. Individual crystals over 10 metres long have been found, and many of the worlds largest crystals were found within pegmatites and these include, microcline and tourmaline. Similarly, crystal texture and form within pegmatitic rock may be taken to extreme size, perthite feldspar within a pegmatite often shows gigantic perthitic texture visible to the naked eye. The single feature that is diagnostic to all pegmatites is their large size crystal components, Pegmatite bodies are usually of minor size compared to typical intrusive rock bodies.
Pegmatite body size is on the order of magnitude of one to a few hundred meters, compared to typical igneous rocks they are rather inhomogeneous and may show zones with different mineral assemblages. Crystal size and mineral assemblages are usually oriented parallel to the rock or even concentric for pegmatite lenses. Crystal growth rates in pegmatite must be slow to allow gigantic crystals to grow within the confines and pressures of the Earths crust. The mineralogy of a pegmatite is in most cases dominated by some form of feldspar, often with mica and usually with quartz and this is because of the difficulty in counting and sampling mineral grains in a rock which may have crystals from centimeters to meters across. Garnet, commonly almandine or spessartine, is a common mineral within pegmatites intruding mafic, pegmatites associated with granitic domes within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain red and brown almandine garnet. Syenite pegmatites are quartz depleted and contain large feldspathoid crystals instead, Pegmatite is difficult to sample representatively due to the large size of the constituent mineral crystals.
Often, bulk samples of some 50–60 kg of rock must be crushed to obtain a meaningful, pegmatite is often characterised by sampling the individual minerals which comprise the pegmatite, and comparisons are made according to mineral chemistry. Occasionally, enrichment in the trace elements will result in crystallisation of equally unusual and rare minerals such as beryl, columbite, zinnwaldite. Pegmatites are the source of lithium either as spodumene, lithiophyllite or usually from lepidolite. The primary source for caesium is pollucite, a mineral from a zoned pegmatite, the majority of the worlds beryllium is sourced from non-gem quality beryl within pegmatite. Tantalum, rare-earth elements are sourced from a few pegmatites worldwide, bismuth and tin have been won from pegmatite, but this is not yet an important source of these metals
Pyroxene
The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes are silicon-aluminum oxides with Ca, Na, Fe, Mg, Zn, Mn, Li substituting for Si, although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes. They share a structure consisting of single chains of silica tetrahedra. The name pyroxene is derived from the Ancient Greek words for fire, they are simply early-forming minerals that crystallized before the lava erupted. The upper mantle of Earth is composed mainly of olivine and pyroxene, a piece of the mantle is shown at right and is dominated by olivine, typical for common peridotite. Pyroxene and feldspar are the minerals in basalt and gabbro. Pyroxene minerals are named according to the chemical species occupying the X site, the Y site, cations in Y site are closely bound to 6 oxygens in octahedral coordination. Cations in the X site can be coordinated with 6 to 8 oxygen atoms, twenty mineral names are recognised by the International Mineralogical Associations Commission on New Minerals and Mineral Names and 105 previously used names have been discarded. A typical pyroxene has mostly silicon in the site and predominately ions with a charge of +2 in both the X and Y sites, giving the approximate formula XYT2O6.
The names of the common calcium – iron – magnesium pyroxenes are defined in the pyroxene quadrilateral shown in Figure 2, the enstatite-ferrosilite series contain up to 5 mol. % calcium and exists in three polymorphs, orthorhombic orthoenstatite and protoenstatite and monoclinic clinoenstatite. Increasing the calcium content prevents the formation of the orthorhombic phases, there is not complete solid solution in calcium content and Mg-Fe-Ca pyroxenes with calcium contents between about 15 and 25 mol. % are not stable with respect to a pair of exolved crystals. This leads to a miscibility gap between pigeonite and augite compositions, there is an arbitrary separation between augite and the diopside-hedenbergite solid solution. The divide is taken at >45 mol. % Ca, as the calcium ion cannot occupy the Y site, pyroxenes with more than 50 mol. % calcium are not possible. A related mineral wollastonite has the formula of the hypothetical calcium end member, magnesium and iron are by no means the only cations that can occupy the X and Y sites in the pyroxene structure. A second important series of minerals are the sodium-rich pyroxenes.
The inclusion of sodium, which has a charge of +1, in jadeite and aegirine this is added by the inclusion of a +3 cation on the Y site. Table 1 shows the range of other cations that can be accommodated in the pyroxene structure. For example, Na and Al give the jadeite composition, coupled substitution of a 1+ ion on the X site and a mixture of equal numbers of 2+ and 4+ ions on the Y site
Magnetite
Magnetite is a mineral and one of the main iron ores. With the chemical formula Fe3O4, it is one of the oxides of iron, Magnetite is ferrimagnetic, it is attracted to a magnet and can be magnetized to become a permanent magnet itself. It is the most magnetic of all the minerals on Earth. Naturally-magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, today it is mined as iron ore. Small grains of magnetite occur in almost all igneous and metamorphic rocks, Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak. The chemical IUPAC name is iron oxide and the chemical name is ferrous-ferric oxide. In addition to rocks, magnetite occurs in sedimentary rocks, including banded iron formations and in lake. Magnetite nanoparticles are thought to form in soils, where they probably oxidize rapidly to maghemite, Magnetite has an inverse spinel crystal structure. As a member of the group, it can form solid solutions with similarly structured minerals, including ulvospinel.
Titanomagnetite, known as titaniferous magnetite, is a solution between magnetite and ulvospinel that crystallizes in many mafic igneous rocks. Titanomagnetite may undergo oxyexsolution during cooling, resulting in ingrowths of magnetite and ilmenite, Magnetite has been important in understanding the conditions under which rocks form. Magnetite reacts with oxygen to produce hematite, and the pair forms a buffer that can control oxygen fugacity. Commonly, igneous rocks contain solid solutions of both titanomagnetite and hemoilmenite or titanohematite, Magnetite is produced from peridotites and dunites by serpentinization. Lodestones were used as a form of magnetic compass. At low temperatures, magnetite undergoes a crystal structure phase transition from a structure to a cubic structure known as the Verwey transition. The Verwey transition occurs around 121 K and is dependent on size, domain state. An isotropic point occurs near the Verwey transition around 130 K, the Curie temperature of magnetite is 858 K.
Magnetite is sometimes found in large quantities in beach sand. Such black sands are found in places, such as Lung Kwu Tan of Hong Kong, California of the United States
Augite
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 contain significant aluminium, with declining temperature, augite may exsolve lamellae of pigeonite and/or orthopyroxene. There is 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 and basalt. It occurs in relatively high-temperature metamorphic rocks such as mafic granulite and it commonly occurs in association with orthoclase, labradorite, leucite 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
Anorthosite
Anorthosite is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar, and a minimal mafic component. Pyroxene, ilmenite and olivine are the minerals most commonly present. Anorthosite on Earth can be divided into two types, Proterozoic anorthosite and Archean anorthosite and these two types of anorthosite have different modes of occurrence, appear to be restricted to different periods in Earths history, and are thought to have had different origins. Lunar anorthosites constitute the areas of the Moons surface and have been the subject of much research. Proterozoic anorthosites were emplaced during the Proterozoic Eon, Anorthosite plutons occur in a wide range of sizes. Some smaller plutons, exemplified by many bodies in the U. S. and Harris in Scotland. Larger plutons, like the Mt. Lister Anorthosite, in northern Labrador, many Proterozoic anorthosites occur in spatial association with other highly distinctive, contemporaneous rock types. These rock types include iron-rich diorite and norite, leucocratic mafic rocks such as leucotroctolite and leuconorite, large volumes of ultramafic rocks are not found in association with Proterozoic anorthosites.
Occurrences of Proterozoic anorthosites are commonly referred to as massifs, there is some question as to what name would best describe any occurrence of anorthosite together with the rock types mentioned above. Batholith is used to such occurrences for the remainder of this article. The areal extent of anorthosite batholiths ranges from small to nearly 20,000 km2, in the instance of the Nain Plutonic Suite in northern Labrador. Major occurrences of Proterozoic anorthosite are found in the southwest U. S. the Appalachian Mountains, eastern Canada, across southern Scandinavia and eastern Europe. Mapped onto the Pangaean continental configuration of that eon, these occurrences are all contained in a single straight belt, the conditions and constraints of this pattern of origin and distribution are not clear. However, see the Origins section below, Anorthosites are common in layered intrusions. Anorthosite in these layered intrusions can form as cumulate layers in the parts of the intrusive complex or as later-stage intrusions into the layered intrusion complex.
Since they are composed of plagioclase feldspar, most of Proterozoic anorthosites appear, in outcrop. Individual plagioclase crystals may be black, blue, or grey, the feldspar variety labradorite is commonly present in anorthosites. Mineralogically, labradorite is a term for any calcium-rich plagioclase feldspar containing 50–70 molecular percent anorthite
Earth
Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes and other sources of water that contribute to the hydrosphere.
The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe.
It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
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 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, the legal system within Scotland has 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 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 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
Diabase
Diabase or dolerite or microgabbro is a mafic, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine grained to aphanitic chilled margins which may contain tachylite. Diabase normally has a fine, but visible texture of euhedral lath-shaped plagioclase crystals set in a matrix of clinopyroxene, typically augite, with minor olivine, magnetite. Accessory and alteration minerals include hornblende, apatite, chalcopyrite, chlorite, the texture is termed diabasic and is typical of diabases. This diabasic texture is termed interstitial, the feldspar is high in anorthite, the calcium endmember of the plagioclase anorthite-albite solid solution series, most commonly labradorite. Diabase is usually found in relatively shallow intrusive bodies such as dikes. Diabase dikes occur in regions of crustal extension and often occur in swarms of hundreds of individual dikes or sills radiating from a single volcanic center.
The Palisades Sill which makes up the New Jersey Palisades on the Hudson River, parts of the Deccan Traps of India, formed at the end of the Cretaceous includes dolerite. It is abundant in parts of Curaçao, an island off the coast of Venezuela. West of the Norseman–Wiluna Belt is the Yalgoo–Singleton Belt, where complex dolerite dike swarms obscure the volcaniclastic sediments, large dolerite sills such as the Golden Mile Dolerite can exhibit course grained texture, and show a large diversity in petrography and geochemistry across the width of the sill. The vast areas of mafic volcanism/plutonism associated with the Jurassic breakup of Gondwanaland in the Southern Hemisphere include many large diabase/dolerite sills and dike swarms. These include the Karoo dolerites of South Africa, the Ferrar Dolerites of Antarctica, in Tasmania dolerite dominates much of the landscape, particularly alpine areas. Ring dikes are large, near vertical dikes showing above ground as circular outcrops up to 30 km in diameter, thicker dikes are made up of plutonic rocks, rather than hypabyssal and are centred on deep intrusions.
Diabase is crushed and used as an aggregate for road beds, railroad beds. Diabase can be cut for use as as ornamental stone for countertops, facing stone on buildings, a form of dolerite, known as bluestone, is one of the materials used as in the construction of Stonehenge. In Tasmania, being one of the most common rocks found, it has used as a building stone, for landscaping. List of rock types Collection of dikes in the Fish River Canyon, Namibia
