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33-498: The Sivalik Hills , also known as Churia Hills , are a mountain range of the outer Himalayas . The literal translation of "Sivalik" is 'tresses of Shiva '. The hills are known for their numerous fossils, and is also home to the Soanian Middle Paleolithic archaeological culture. The Sivalik Hills are a mountain range of the outer Himalayas that stretches over about 2,400 km (1,500 mi) from

66-482: A rock unit is a description of its physical characteristics visible at outcrop , in hand or core samples , or with low magnification microscopy. Physical characteristics include colour, texture, grain size , and composition. Lithology may refer to either a detailed description of these characteristics, or a summary of the gross physical character of a rock. Examples of lithologies in the second sense include sandstone , slate , basalt , or limestone . Lithology

99-409: A body of water or beneath ice. Unconsolidated surficial materials may also be given a lithology. This is defined by grain size and composition and is often attached to an interpretation of how the unit formed. Surficial lithologies can be given to lacustrine , coastal, fluvial , aeolian , glacial , and recent volcanic deposits, among others. Examples of surficial lithology classifications used by

132-411: A continually-increasing extent of metamorphism. Metamorphic facies are defined by the pressure-temperature fields in which particular minerals form. Additional metamorphic rock names exist, such as greenschist (metamorphosed basalt and other extrusive igneous rock) or quartzite (metamorphosed quartz sand). In igneous and metamorphic rocks, grain size is a measure of the sizes of the crystals in

165-408: A hand lens, the visible mineralogy is included as part of the description. In the case of sequences possibly including carbonates , calcite - cemented rocks or those with possible calcite veins, it is normal to test for the presence of calcite (or other forms of calcium carbonate ) using dilute hydrochloric acid and looking for effervescence . The mineralogical composition of a rock is one of

198-461: A particular depositional environment and may provide information on paleocurrent directions. In metamorphic rocks associated with the deeper levels of fault zones , small scale structures such as asymmetric boudins and microfolds are used to determine the sense of displacement across the zone. In igneous rocks, small-scale structures are mostly observed in lavas such as pahoehoe versus ʻAʻā basaltic flows, and pillows showing eruption within

231-569: A rock describes the relationship between the individual grains or clasts that make up the rock. Sedimentary textures include the degree of sorting , grading , shape and roundness of the clasts. Metamorphic textures include those referring to the timing of growth of large metamorphic minerals relative to a phase of deformation—before deformation porphyroclast —after deformation porphyroblast . Igneous textures include such properties as grain shape, which varies from crystals with ideal crystal shapes ( euhedral ) to irregular crystals (anhedral), whether

264-636: A sample. The colour of a rock or its component parts is a distinctive characteristic of some rocks and is always recorded, sometimes against standard colour charts, such as that produced by the Rock-Color Chart Committee of the Geological Society of America based on the Munsell color system . The fabric of a rock describes the spatial and geometric configuration of all the elements that make it up. In sedimentary rocks

297-639: Is a mixture of molten rock, dissolved gases, and solid crystals. Sedimentary rock is formed from mineral or organic particles that collect at the Earth's surface and become lithified . Metamorphic rock forms by recrystallization of existing solid rock under conditions of great heat or pressure. Igneous rocks are further broken into three broad categories. Igneous rock composed of broken rock fragments created directly by volcanic processes ( tephra ) are classified as pyroclastic rock . Pyroclastic rocks are further classified by average fragment ( clast ) size and whether

330-538: Is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains. The early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet (3,000 m) of mostly Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to

363-540: Is impractical, they may be classified chemically using the TAS classification . This is based on the total content of silica and alkali metal oxides and other chemical criteria. Sedimentary rocks are further classified by whether they are siliciclastic or carbonate . Siliciclastic sedimentary rocks are then subcategorized based on their grain size distribution and the relative proportions of quartz, feldspar, and lithic (rock) fragments. Carbonate rocks are classified with

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396-557: Is the basis of subdividing rock sequences into individual lithostratigraphic units for the purposes of mapping and correlation between areas. In certain applications, such as site investigations , lithology is described using a standard terminology such as in the European geotechnical standard Eurocode 7 . The naming of a lithology is based on the rock type . The three major rock types are igneous , sedimentary , and metamorphic . Igneous rocks are formed directly from magma , which

429-477: Is the diameter of the grains and/or clasts that constitute the rock. These are used to determine which rock naming system to use (e.g., a conglomerate , sandstone , or mudstone ). In the case of sandstones and conglomerates, which cover a wide range of grain sizes, a word describing the grain size range is added to the rock name. Examples are " pebble conglomerate" and "fine quartz arenite ". In rocks in which mineral grains are large enough to be identified using

462-865: The Alpide belt . The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera , the Aleutian Range , on through Kamchatka Peninsula , Japan , Taiwan , the Philippines , Papua New Guinea , to New Zealand . The Andes is 7,000 kilometres (4,350 mi) long and is often considered the world's longest mountain system. The Alpide belt stretches 15,000 km across southern Eurasia , from Java in Maritime Southeast Asia to

495-551: The Annamite Range . If the definition of a mountain range is stretched to include underwater mountains, then the Ocean Ridge forms the longest continuous mountain system on Earth, with a length of 65,000 kilometres (40,400 mi). The position of mountain ranges influences climate, such as rain or snow. When air masses move up and over mountains, the air cools, producing orographic precipitation (rain or snow). As

528-475: The Dunham or Folk classification schemes according to the constituents of the carbonate rock. Metamorphic rock naming can be based on protolith , mineral composition, texture, or metamorphic facies . Naming based on texture and a pelite (e.g., shale , mudrock ) protolith can be used to define slate and phyllite . Texture-based names are schist and gneiss . These textures, from slate to gneiss, define

561-628: The Early Miocene , until the Middle Pleistocene , around 18 million to 600,000 years ago. Some of the best known fossils from the hills include Megalochelys atlas , the largest known tortoise to have ever existed, Sivatherium giganteum , the largest known giraffid , and the ape Sivapithecus . Remains of the Lower - Middle Paleolithic Soanian culture dating to around 500,000 to 125,000 years Before Present were found in

594-804: The Iberian Peninsula in Western Europe , including the ranges of the Himalayas , Karakoram , Hindu Kush , Alborz , Caucasus , and the Alps . The Himalayas contain the highest mountains in the world, including Mount Everest , which is 8,848 metres (29,029 ft) high. Mountain ranges outside these two systems include the Arctic Cordillera , Appalachians , Great Dividing Range , East Siberians , Altais , Scandinavians , Qinling , Western Ghats , Vindhyas , Byrrangas , and

627-710: The Indus River eastwards close to the Brahmaputra River , spanning the northern parts of the Indian subcontinent . It is 10–50 km (6.2–31.1 mi) wide with an average elevation of 1,500–2,000 m (4,900–6,600 ft). Between the Teesta and Raidāk Rivers in Assam is a gap of about 90 km (56 mi). They are well known for their Neogene and Pleistocene aged vertebrate fossils. Geologically,

660-568: The Mithrim Montes and Doom Mons on Titan, and Tenzing Montes and Hillary Montes on Pluto. Some terrestrial planets other than Earth also exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars . Jupiter's moon Io has mountain ranges formed from tectonic processes including the Boösaule , Dorian, Hi'iaka and Euboea Montes . Lithology The lithology of

693-464: The QAPF classification , which is based on the relative content of quartz , alkali feldspar , plagioclase , and feldspathoid . Special classifications exist for igneous rock of unusual compositions, such as ultramafic rock or carbonatites . Where possible, extrusive igneous rocks are also classified by mineral content using the extrusive QAPF classification, but when determining the mineral composition

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726-630: The Main Frontal Thrust, with steeper slopes on that side. Below this, the coarse alluvial Bhabar zone makes the transition to the nearly level plains. Rainfall, especially during the summer monsoon , percolates into the Bhabar, then is forced to the surface by finer alluvial layers below it in a zone of springs and marshes along the northern edge of the Terai or plains. The Sivalik Hills are well known for fossils of vertebrates, spanning from

759-578: The Sivalik Hills belong to the Tertiary deposits of the outer Himalayas. They are chiefly composed of sandstone and conglomerate rock formations, which are the solidified detritus of the Himalayas to their north; they are poorly consolidated. The sedimentary rocks comprising the hills are believed to be 16–5.2 million years old. They are bounded on the south by a fault system called

792-931: The Sivalik region. Contemporary to the Acheulean , the Soanian culture is named after the Soan Valley in the Sivalik Hills of Pakistan . The Soanian archaeological culture is found across Sivalik region in present-day India, Nepal and Pakistan. The carbon stock and carbon sequestration rates of the Churia forests differ among different forest management regimes and are highest in protected areas. 27°46′N 82°24′E  /  27.767°N 82.400°E  / 27.767; 82.400 Mountain range Mountain ranges are usually segmented by highlands or mountain passes and valleys . Individual mountains within

825-627: The air descends on the leeward side, it warms again (following the adiabatic lapse rate ) and is drier, having been stripped of much of its moisture. Often, a rain shadow will affect the leeward side of a range. As a consequence, large mountain ranges, such as the Andes, compartmentalize continents into distinct climate regions . Mountain ranges are constantly subjected to erosional forces which work to tear them down. The basins adjacent to an eroding mountain range are then filled with sediments that are buried and turned into sedimentary rock . Erosion

858-485: The east. This mass of rock was removed as the range was actively undergoing uplift. The removal of such a mass from the core of the range most likely caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment. Computer simulation has shown that as mountain belts change from tectonically active to inactive,

891-440: The fragments are mostly individual mineral crystals , particles of volcanic glass , or rock fragments. Further classifications, such as by chemical composition , may also be applied. Igneous rocks that have visible mineral grains ( phaneritic rocks) are classified as intrusive , while those that are glassy or very fine-grained ( aphanitic ) are classified as extrusive rock . Intrusive igneous rocks are usually classified using

924-454: The main visible fabric is normally bedding , and the scale and degree of development of the bedding is normally recorded as part of the description. Metamorphic rocks (apart from those created by contact metamorphism ), are characterised by well-developed planar and linear fabrics. Igneous rocks may also have fabrics as a result of flow or the settling out of particular mineral phases during crystallisation, forming cumulates . The texture of

957-487: The major ways in which it is classified. Igneous rocks are classified by their mineral content whenever practical, using the QAPF classification or special ultramafic or carbonatite classifications. Likewise metamorphic facies, which show the degree to which a rock has been exposed to heat and pressure and are therefore important in classifying metamorphic rocks, are determined by observing the mineral phases that are present in

990-627: The rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System, including the Moon , are often isolated and formed mainly by processes such as impacts, though there are examples of mountain ranges (or "Montes") somewhat similar to those on Earth. Saturn 's moon Titan and Pluto , in particular, exhibit large mountain ranges in chains composed mainly of ices rather than rock. Examples include

1023-401: The rock shows highly nonuniform crystal sizes (is porphyritic ), or whether grains are aligned (which is described as trachytic texture). Rocks often contain small-scale structures (smaller than the scale of an individual outcrop). In sedimentary rocks this may include sole markings , ripple marks , mudcracks and cross-bedding . These are recorded as they are generally characteristic of

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1056-478: The rock. In igneous rock, this is used to determine the rate at which the material cooled: large crystals typically indicate intrusive igneous rock, while small crystals indicate that the rock was extrusive. Metamorphism of rock composed of mostly a single mineral, such as quartzite or marble , may increase grain size ( grain growth ), while metamorphism of sheared rock may decrease grain size (syntectonic recrystallization ). In clastic sedimentary rocks, grain size

1089-479: The same mountain range do not necessarily have the same geologic structure or petrology . They may be a mix of different orogenic expressions and terranes , for example thrust sheets , uplifted blocks , fold mountains, and volcanic landforms resulting in a variety of rock types . Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or

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