Igneous rock - Igneous rock Igneous rocks are formed when molten rock (magma derived from the mantle, or, pre-existing rocks molten by extreme temperature) cools and solidifies, with or without crystallization. Over 700 types of igneous rocks have been described, most of them intrusive. Igneous rock are geologically important because: their minerals and global chemistry gives information about the composition of the mantle where they were extracted from, and the temperature and pressure conditions that allowed this extraction, or (below) their minerals and global chemistry gives information about the composition of the country pre-existing rock that melted their absolute ages can be obtained from various forms of radiometric dating and thus can be compared to adjacent strata, allowing a time sequence of events their features are usually characteristic of.
Sedimentary rock - Sedimentary rock Sedimentary rock is formed from the weathered remains of other rocks. Sedimentary rocks are formed from overburden pressure as particles of sediment are deposited out of air, ice, or water flows carrying the particles in suspension. As sediment deposition builds up, the overburden (or lithostatic) pressure squeezes the sediment into layered solids in a process known as lithification ("rock formation") and the original connate fluids are expelled. Sedimentary rocks are composed largely of silica (i.e. quartz), with other common minerals including feldspars, amphiboles, clay minerals and sometimes more exotic igneous minerals. Sedimentary rocks are classified as clastic, that is, they are composed of discrete clasts of material (rather than being composed of organic material as is the case for a limestone). Carbonate minerals precipitating out.
Rock (geology) - Rock (geology) Rock is a substance composed of minerals and classified according to mineral composition. Rocks are generally classified by the processes that formed them, and are thus separated into igneous, sedimentary, and metamorphic rocks. Igneous rocks are formed from molten magma, sedimentary rocks by deposition and compression of particulate matter, and metamorphic rocks by either of the first two categories after being changed by the effects of temperature and pressure. In cases where organic material leaves behind an imprint of itself in rock, the result is known as a fossil. See also: List of rocks List of minerals and stone types List of stone Quarrying Rock used in sculpting..
Metamorphic rock - Metamorphic rock Metamorphic rock are the result of the transformation of a pre-existing rock type, the protolith, in a process is called metamorphism. The nature of the protolith can be either sedimentary, igneous or older metamorphic rocks. Metamorphic rocks can be classified according texture or mineral assembly (metamorphic facies). See also: List of minerals, rock (geology), List of rocks.
List of rocks - of rocks This page is intended as a list of all rock types. See also: List of minerals -- List of stone -- Earth science -- mineralogy -- mineraloid -- rock -- metamorphic rock -- igneous rock -- sedimentary rock Sorted by name: Table of contents showTocToggle("show","hide") 1 A 2 B 3 C 4 D 5 E 6 F 7 G 8 H 9 I 10 J 11 K 12 L 13 M 14 N 15 O 16 P 17 Q 18 R 19 S 20 T 21 U 22 V 23 W 24 X 25 Y 26 Z 27 External Links A Amphibolite Andesite Anorthosite Aplite B Basalt Basanite Blue schist Breccia C Chert Clay Coal Concretion Conglomerate D Dacite Dendrite Diatomite Diorite Dolomite Dunite E Eclogite Epidiorite Epidosite Evaporite.
Island arc - the upper mantle. When melted this material becomes very boyant and rises up to the surface where it becomes lava and forms volcanos in the shape of an arc. Due to the reactions of the metamorphic and igneous rocks, it is not uncommon to find black-green beaches composed of olivine eroded from volcanic cones. On the ocean side of the island arc is a deep trench where the subducted plate sinks below the subducting plate. This trench is created by the friction of the subducting plate pulling the leading edge of the overbearing plate downward. Great frictinal forces heat the rock on both plates in this area. Oceans that are being reduced by the subduction of plates are called 'remnant oceans' as they will slowly be shrunken out of existence. This.
Gabbro - Gabbro is a dark, coarse-grained intrusive igneous rock chemically equivalent to basalt. It is a plutonic rock, formed when molten magma is trapped beneath the Earth's surface and cools slowly into a hard, coarsely crystalline mass. It is dense, greenish or dark-colored and contains varied percentages of plagioclase feldspar, pyroxene, amphibole, and olivine (called olivine gabbro when olivine is present in large quantities). Quartz gabbros are also known to occur and are probably derived from magma that was oversaturated with silica. On the other hand, essexites represent gabbros whose parent magma had an insufficiency of silica resulting in the formation of nephelite. Gabbro is too fragile to use in construction, but often contains valuable amounts of chromium, nickel, cobalt, gold, silver, platinum, and copper sulfides. See also: List of minerals.
Geography of Ethiopia - the depression in which is Lake Rudolf and---east of that lake--southern Somaliland. The western wall of the plateau from 6 deg. N. to 11 deg. N. is well marked and precipitous. North of 11 deg. N. the hills turn more to the east and fall more gradually to the plains at their base. On its northern face also the plateau falls in terraces to the level of the eastern Sudan. The eastern escarpment is the best defined of these outer ranges. It has a mean height of from 7000 to 8000 ft., and in many places rises almost perpendicularly from the plain. Narrow and deep clefts, through which descend mountain torrents to lose themselves in the sandy soil of the coast land, afford means of reaching the plateau, or the easier.
Geology of the Alps - is very clearly defined; nowhere does the Molasse pass beyond it to the south and nowhere does the Flysch extend beyond it to the north. The Molasse, in the neighbourhood of the mountains, consists chiefly of conglomerates and sandstones, and the Flysch consists of sandstones and shales; but the Molasse is of Miocene and Oligocene age, while the Flysch is mainly Eocene. The relations of the two series are never normal. Along the line of contact, which is often a fault, the oldest beds of the Molasse crop out, and they are invariably overturned and plunge beneath the Flysch. A few miles farther north these same beds rise again to the surface at the summit of an anticlinal which runs parallel to the chain. Beyond this point all signs of folding.
Geography of the Eastern United States - coast. Please refer to the Geography of the United States for the other areas. The Appalachain Highlands includes not just the Appalachian Mountains, but also the surrounding plateaus and valleys. The physiographic description of the system consists essentially of two belts: one on the southeast - folded strata. one on the northwest - largely crystalline rocks. The southeast portion is largely composed of ancient and greatly deformed crystalline rocks (e.g. igneous and metamorphic), while the northwest portion is a heavy series of folded Palaeozoic strata. It is convenient to associate a third belt, farther northwest, consisting of the same Palaeozoic strata but ying essentially horizontal. This belt constitutes the Appalachian plateau. At least in part, the crystalline belt represents the ancient highlands from whose ruins the sedimentary sandstones, shales and limestones.
Gneiss - derived by metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. Gneissic rocks are coarsely laminated and 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, etc. However, depending on their composition, they may also be called garnet gneiss, biotite gneiss, albite gneiss, etc. Orthogneiss designates a gneiss derived from an igneous rock and paragneiss one from a sedimentary rock. The word "gneiss" is from an old Saxon mining term which seems to have meant decayed or rotten, or possibly worthless material. See also: List of rocks.
Gondwana (India) - can also be found in other parts of India). It has given its name to the ancient continent of Gondwanaland because some of the earliest rock formations of this continent were first investigated in part of the region, in modern Orissa. As Gonds are spread widely across central India, and are a minority almost everywhere, there is no unambiguous boundary to the region. However, the core region can be considered to be the eastern part of the Vidarbha region of Maharashtra, the parts of Madhya Pradesh immediately to the north of it, and parts of the west of Chhattisgarh. The wider region extends beyond these, also including parts of northern Andhra Pradesh, and western Orissa. The region is part of the northern Deccan plateau, with an average height of about 6-700.
Granite - a common and widely-occurring group of intrusive felsic igneous rocks that forms at great depths and pressures under continents. Granite consists of orthoclase, plagioclase quartz, hornblende, biotite, muscovite and minor accessories such as magnetite, garnet, zircon and apatite minerals. Rarely a pyroxene is present. Ordinary granite always carries a small amount of plagioclase, but when this is absent the rock is referred to as alkali granite. An increasing proportion of plagioclase feldspar causes granite to pass into granodiorite. A rock consisting of equal proportions of orthoclase and plagioclase plus quartz may be considered a quartz monozonite. A granite containing both muscovite and biotite micas is called a binary granite. The word granite comes from the Latin granum, a grain, in reference to the grained structure of such a crystalline rock. Granite.
Feldspar - Feldspar (from the German Feld, field, and Spat, a rock that does not contain ore) is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earth's crust. They crystallize from magma in both intrusive and extrusive rocks; they occur as compact minerals, as veins, and are developed in many types of metamorphic rock. They may also be found in many types of sedimentary rock. This group of minerals consists of three silicates: a potassium-aluminium silicate (the orthoclase feldspars), a sodium-aluminium silicate, and a calcium-aluminium silicate (the plagioclase feldspars) and their isomorphous mixtures. Orthoclase feldspars Orthoclase (KAlSi3O8) is named based on the Greek for "straight fracture," because its two cleavages are at right angles to each other. It has a hardness of.
Fluorite - cm (2 inches) long. Octahedral fluorite crystals. Fluorite may occur as a vein deposit, especially with metallic minerals, where it often forms a part of the gangue (the worthless `host-rock' in which valuable minerals occur) and may be associated with barite, quartz and calcite. It is a common mineral in deposits of pneumatolytic origin and has been noted as a primary mineral in granites and other igneous rocks. Blue John One of the most famous of the older localities of fluorite is Derbyshire, England, where under the name of Derbyshire Blue John beautiful blue fluorite is used for ornamental purposes; its softness, however, has been a bar to general use. Uses As well as ornamental uses, fluorite is also used as a flux in the manufacture of steel, in the making.
Extrusive (geology) - Extrusive (geology) Extrusive refers to a mode of igneous rock (geology) formation, in which hot magma from inside the earth flows out (extrudes) onto the surface. The main effect of extrusion is that the magma can cool much more quickly in the open air, and there is little time for the growth of crystals. Often, a residual portion of the groundmass (geology) fails to crystalize at all, instead becoming an interstitial glass. If the magma contains free gas, which is common, then it may cool with large and small bubble shaped cavities, or the rock may be porous..
Dunite - Dunite Dunite is an igneous, plutonic (intrusive) rock, of ultramafic composition, with phaneritic texture. Mineral assembly is composed typically of > 90% olivine. Dunitic rocks are believed to represent the Earth's mantle. Typically, dunites occur at the base of ophiolite sequences. See also: igneous rocks, list of rocks.
Dacite - Volcanic National Park , Dacite is an igneous, volcanic (extrusive) rock, of felsic composition, with aphanitic to porphyritic texture. Mineral assembly is usually quartz, alkali feldspar and plagioclase (in a ratio < 1:2). Quartz and alkali feldspars may be scarce. Biotite, hornblende and pyroxene are common accessory minerals. See also: igneous rocks, list of rocks.
Aberdeenshire - Don. A valuable pearl in the Scottish crown is said to be from the Ythan. Loch Muick, the largest of the few lakes in the county, 1310 feet above the sea, 2½ miles long and 1/3 to ½ miles broad, lies some 8½ miles southwest of Ballater, and has Altnagiuthasach, a royal shooting-box, near its south-western end. Loch Strathbeg, six miles southeast of Fraserburgh, is only separated from the sea by a narrow strip of land. There are noted chalybeate springs at Peterhead, Fraserburgh, and Pannanich near Ballater. Table of contents showTocToggle("show","hide") 1 Geology 2 Flora and Fauna 3 Climate and Agriculture 4 Fisheries 5 Other Industries 6 Communications 7 Population and Government 8 History Geology The greater part of the county is composed of crystalline schists belonging to the metamorphic.
Abraham Gottlob Werner - no evidence that he had ever traveled beyond Saxony in his entire adult life. He died at Dresden from internal complications said to have been caused by his consternation over the misfortunes that had befallen Saxony during the Napoleonic Wars. Werner applied superposition in a classification similar to that of Lehmann. He believed that the earth could be divided into five formations: a. Primitive (Urgebirge) Series - intrusive igneous rocks and high rank metasediments considered to be the first precipitates from the ocean before the emergence of land. b. Transition (Ubergangsgebirge) Series - more indurated limestones, dikes, sills, and thick sequences of greywackes that very the first orderly deposits from the ocean. These were "universal" formations extending without interruption around the world. c. Secondary or Stratified (Flotz) Series - the remaining,.
