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Tibetan Himalayas
The geology of Nepal is dominated by the Himalaya, the highest, youngest and a very highly active mountain range. Himalaya is a type locality for the study of on-going continent-continent collision tectonics. The Himalayan arc extends about from Nanga Parbat () by the Indus River in northern Pakistan eastward to Namche Barwa () by the gorge of the Tsangpo-Brahmaputra in eastern Tibet. About of this extent is in Nepal; the remainder includes Bhutan and parts of Pakistan, India, and China. Since 55 Ma the Himalayan orogeny beginning with the collision of Indian subcontinent and Eurasia at the Paleocene/Eocene epoch, has thickened the Indian crust to its present thickness of . The northwest tip of India after colliding with Asia seems to have met along the full length of the suture by about 40 Ma. Immediately prior to the onset of the Indo-Asian collision, the northern boundary of the Indian shield was likely a thinned continental margin on which Proterozoic clasti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nepal Topo En
Nepal (; ne, नेपाल ), formerly the Federal Democratic Republic of Nepal ( ne, सङ्घीय लोकतान्त्रिक गणतन्त्र नेपाल ), is a landlocked country in South Asia. It is mainly situated in the Himalayas, but also includes parts of the Indo-Gangetic Plain, bordering the Tibet Autonomous Region of China to the north, and India in the south, east, and west, while it is narrowly separated from Bangladesh by the Siliguri Corridor, and from Bhutan by the Indian state of Sikkim. Nepal has a diverse geography, including fertile plains, subalpine forested hills, and eight of the world's ten tallest mountains, including Mount Everest, the highest point on Earth. Nepal is a multi-ethnic, multi-lingual, multi-religious and multi-cultural state, with Nepali as the official language. Kathmandu is the nation's capital and the largest city. The name "Nepal" is first recorded in texts from the Vedic period of the Indi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eurasia
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago and the Russian Far East to the east. The continental landmass is bordered by the Atlantic Ocean and Africa to the west, the Pacific Ocean to the east, the Arctic Ocean to the north, and by Africa, the Mediterranean Sea, and the Indian Ocean to the south. The division between Europe and Asia as two continents is a historical social construct, as many of their borders are over land; thus, in some parts of the world, Eurasia is recognized as the largest of the six, five, or four continents on Earth. In geology, Eurasia is often considered as a single rigid megablock. However, the rigidity of Eurasia is debated based on paleomagnetic data. Eurasia covers around , or around 36.2% of the Earth's total land area. It is also home to the largest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indo-Gangetic Plain
The Indo-Gangetic Plain, also known as the North Indian River Plain, is a fertile plain encompassing northern regions of the Indian subcontinent, including most of northern and eastern India, around half of Pakistan, virtually all of Bangladesh and southern plains of Nepal. The region is named after the Indus and the Ganges rivers and encompasses a number of large urban areas. The plain is bound on the north by the Himalayas, which feed its numerous rivers and are the source of the fertile alluvium deposited across the region by the two river systems. The southern edge of the plain is marked by the Deccan Plateau. On the west rises the Iranian Plateau. Many developed cities like Delhi, Dhaka, Kolkata, Lahore and Karachi are located in the Indo-Gangetic Plain. History The region is known for the Indus Valley civilization, which was responsible for the birth of ancient culture of the Indian subcontinent. The flat and fertile terrain has facilitated the repeated rise and expans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terai
The Terai or Tarai is a lowland region in northern India and southern Nepal that lies south of the outer foothills of the Himalayas, the Sivalik Hills, and north of the Indo-Gangetic Plain. This lowland belt is characterised by tall grasslands, scrub savannah, Shorea robusta, sal forests and clay rich swamps. In North India, the Terai spreads from the Yamuna River eastward across Haryana, Uttarakhand, Uttar Pradesh, Bihar and West Bengal. The Terai is part of the Terai-Duar savanna and grasslands ecoregion. The corresponding lowland region in West Bengal, Bangladesh, Bhutan and Assam in the Brahmaputra River basin is called 'Dooars'. In Nepal, the term is applied to the part of the country situated north of the Indo-Gangetic Plain. Nepal's Terai stretches over , about 23.1% of Nepal's land area, and lies at an elevation of between . The region comprises more than 50 wetlands. North of the Terai rises the Bhabar, a narrow but continuous belt of forest about wide. Etymology The Urdu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratigraphy
Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostratigraphy (lithologic stratigraphy), biostratigraphy (biologic stratigraphy), and chronostratigraphy (stratigraphy by age). Historical development Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition, the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. The first practical large-scale application of stratigraphy was by William Smith (geologist), William Smith in the 1790s and early 19th century. Known as the "Father of English geology", Smith recognized the significance of Stratum, strata or rock layering and the importance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectonostratigraphy
In geology, tectonostratigraphy is stratigraphy that refers either to rock sequences in which large-scale layering is caused by the stacking of thrust sheets, or nappes, in areas of thrust tectonics or to the effects of tectonics on lithostratigraphy. Tectonically formed stratigraphy One example of such a tectonostratigraphy is the Scandinavian Caledonides. Within the entire exposed 1800 km length of this orogenic belt the following sequence is recognised from the base upwards: * Autochthon : undisturbed foreland of the Baltic plate * Parautochthon : thrust sheets that have moved only a short distance (up to 10s of km) from their original position * Lower allochthon : far travelled thrust sheets derived from the Baltic plate passive margin, mainly sediments associated with the break-up of Rodinia * Middle allochthon : also derived from the margin of the Baltic plate, Proterozoic basement and its psammitic cover * Upper allochthon : thrust sheets including island arc and oph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tethys Ocean
The Tethys Ocean ( el, Τηθύς ''Tēthús''), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean that covered most of the Earth during much of the Mesozoic Era and early Cenozoic Era, located between the ancient continents of Gondwana and Laurasia, before the opening of the Indian and Atlantic oceans during the Cretaceous Period. It was preceded by the Paleo-Tethys Ocean, which lasted between the Cambrian and the Early Triassic, while the Neotethys formed during the Late Triassic and lasted until the early Eocene (about 50 million years ago) when it completely closed. A portion known as the Paratethys formed during the Late Jurassic, was isolated during the Oligocene (34 million years ago) and lasted up to the Pliocene (about 5 million years ago), when it largely dried out. Many major seas and lakes of Europe and Western Asia, including the Mediterranean Sea, the Black Sea, the Caspian Sea, and the Aral Sea are thought to be remnants of the Paratethys. Ety ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian
The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clastic Rock
Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks by physical weathering.Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-5 Geologists use the term clastic to refer to sedimentary rocks and particles in sediment transport, whether in suspension or as bed load, and in sediment deposits. Sedimentary clastic rocks Clastic sedimentary rocks are rocks composed predominantly of broken pieces or ''clasts'' of older weathered and eroded rocks. Clastic sediments or sedimentary rocks are classified based on grain size, clast and cementing material (matrix) composition, and texture. The classification factors are often useful in determining a sample's environment of deposition. An example of clastic environment would be a river system in which the full range of grains being transported by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proterozoic
The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic. The Proterozoic covers the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth. The name ''Proterozoic'' combines two forms of ultimately Greek origin: meaning 'former, earlier', and , 'of life'. The well-identified events of this eon were the transition to an oxygenated atmosphere during the Paleoproterozoic; the evolution of eukaryotes; several glaciations, which produced the hypothesized Snowball Earth during the Cryogenian Period in the late Neoproterozoic Era; and the Ediacaran Period (635 to 538.8 Ma) which is characterize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continental Margin
A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin consists of three different features: the continental rise, the continental slope, and the continental shelf. The continental shelf is the relatively shallow water area found in proximity to continents. Continental margins constitute about 28% of the oceanic area. Zones of the continental margin The continental shelf is the portion of the continental margin that transitions from the shore out towards to ocean. Continental shelves are believed to make up 7% of the sea floor. The width of continental shelves worldwide varies in the range of 0.03–1500 km. The continental shelf is generally flat, and ends at the shelf break, where there is a drastic increase in slope angle: The mean angle of continental shelves worldwide is 0° 07′, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suture (geology)
In structural geology, a suture is a joining together along a major fault zone, of separate terranes, tectonic units that have different plate tectonic, metamorphic and paleogeographic histories. The suture is often represented on the surface by an orogen or mountain range. Overview In plate tectonics, sutures are the remains of subduction zones, and the terranes that are joined together are interpreted as fragments of different palaeocontinents or tectonic plates. Outcrops of sutures can vary in width from a few hundred meters to a couple of kilometers. They can be networks of mylonitic shear zones or brittle fault zones, but are usually both. Sutures are usually associated with igneous intrusions and tectonic lenses with varying kinds of lithologies from plutonic rocks to ophiolitic fragments. An example from Great Britain is the Iapetus Suture which, though now concealed beneath younger rocks, has been determined by geophysical means to run along a line roughly paralle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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