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Tibesti (departement)
The Tibesti Mountains are a mountain range in the central Sahara, primarily located in the extreme north of Chad, with a small portion located in southern Libya. The highest peak in the range, Emi Koussi, lies to the south at a height of and is the highest point in both Chad and the Sahara. Bikku Bitti, the highest peak in Libya, is located in the north of the range. The central third of the Tibesti is of volcanic origin and consists of five volcanoes topped by large depressions: Emi Koussi, Tarso Toon, Tarso Voon, Tarso Yega and Toussidé. Major lava flows have formed vast plateaus that overlie Paleozoic sandstone. The volcanic activity was the result of a continental hotspot that arose during the Oligocene and continued in some places until the Holocene, creating fumaroles, hot springs, mud pools and deposits of natron and sulfur. Erosion has shaped volcanic spires and carved an extensive network of canyons through which run rivers subject to highly irregular flows that are ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tarso Toon
Tarso Toon (sometimes also known as Tarso Toh; "Tarso" means "high plateau".) is a volcano in the central Tibesti mountains. The volcano reaches a maximum height of and a width of , covering a surface of . It also features a caldera wide, with a gap on its northern side. It was active in the Miocene, developing over older ignimbrites with tholeiitic rocks. Later, felsic In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, whi ... volcanic rocks were emplaced within the caldera and the Voon ignimbrite buried parts of the tholeiite. References Sources * External links {{Commons-inline, Tarso Toon See also * Tarso Toh, an unrelated volcano Miocene shield volcanoes Volcanoes of Chad Calderas of Chad Polygenetic shield volcanoes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as ''physical'' or ''mechanical'' erosion; this contrasts with ''chemical'' erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Agents of erosion include rainfall; bedrock wear in rivers; coastal erosion by the sea and waves; glacial plucking, abrasion, and scour; areal flooding; wind abrasion; groundwater processes; and mass movement processes in steep landscapes like landslides and debris flows. The rates at which such processes act control how fast a surface is eroded. Typically, physical erosion procee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Elemental sulfur is a bright yellow, crystalline solid at room temperature. Sulfur is the tenth most abundant element by mass in the universe and the fifth most on Earth. Though sometimes found in pure, native form, sulfur on Earth usually occurs as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, being mentioned for its uses in ancient India, ancient Greece, China, and ancient Egypt. Historically and in literature sulfur is also called brimstone, which means "burning stone". Today, almost all elemental sulfur is produced as a byproduct of removing sulfur-containing contaminants from natural gas and petroleum.. Downloahere The greatest commercial use of the element is the production o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natron
Natron is a naturally occurring mixture of sodium carbonate decahydrate ( Na2CO3·10H2O, a kind of soda ash) and around 17% sodium bicarbonate (also called baking soda, NaHCO3) along with small quantities of sodium chloride and sodium sulfate. Natron is white to colourless when pure, varying to gray or yellow with impurities. Natron deposits are sometimes found in saline lake beds which arose in arid environments. Throughout history natron has had many practical applications that continue today in the wide range of modern uses of its constituent mineral components. In modern mineralogy the term ''natron'' has come to mean only the sodium carbonate decahydrate (hydrated soda ash) that makes up most of the historical salt. Etymology The English and German word ''natron'' is a French cognate derived from the Spanish ''natrón'' through Latin ''natrium'' and Greek ''nitron'' (). This derives from the Ancient Egyptian word ''nṯrj''. ''Natron'' refers to Wadi El Natrun or Natr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mud Pool
A mudpot, or mud pool, is a sort of acidic hot spring, or fumarole, with limited water. It usually takes the form of a pool of bubbling mud. The acid and microorganisms decompose surrounding rock into clay and mud. Description The mud of a mudpot takes the form of a viscous, often bubbling, slurry. As the boiling mud is often squirted over the brims of the mudpot, a sort of mini-volcano of mud starts to build up, sometimes reaching heights of 1 to 1.5 meters. Although mudpots are often called "mud volcanoes", true mud volcanoes are very different in nature. The mud of a mudpot is generally of white to greyish color, but is sometimes stained with reddish or pink spots from iron compounds. When the slurry is particularly colorful, the feature may be referred to as a paint pot. Geology Mudpots form in high-temperature geothermal areas where water is in short supply. The little water that is available rises to the surface at a spot where the soil is rich in volcanic ash, clay, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hot Spring
A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circulation through faults to hot rock deep in the Earth's crust. In either case, the ultimate source of the heat is radioactive decay of naturally occurring radioactive elements in the Earth's mantle, the layer beneath the crust. Hot spring water often contains large amounts of dissolved minerals. The chemistry of hot springs ranges from acid sulfate springs with a pH as low as 0.8, to alkaline chloride springs saturated with silica, to bicarbonate springs saturated with carbon dioxide and carbonate minerals. Some springs also contain abundant dissolved iron. The minerals brought to the surface in hot springs often feed communities of extremophiles, microorganisms adapted to extreme conditions, and it is possible that life on Earth had its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fumaroles
A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcanic activity, but fumarole activity can also precede a volcanic eruption and has been used for eruption prediction. Most fumaroles die down within a few days or weeks of the end of an eruption, but a few are persistent, lasting for decades or longer. An area containing fumaroles is known as a fumarole field. The predominant vapor emitted by fumaroles is steam, formed by the circulation of groundwater through heated rock. This is typically accompanied by volcanic gases given off by magma cooling deep below the surface. These volcanic gases include sulfur compounds, such as various sulfur oxides and hydrogen sulfide, and sometimes hydrogen chloride, hydrogen fluoride, and other gases. A fumarole that emits significant sulfur compounds is some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch, called the Flandrian interglacial.Oxford University Press – Why Geography Matters: More Than Ever (book) – "Holocene Humanity" section https://books.google.com/books?id=7P0_sWIcBNsC The Holocene corresponds with the rapid proliferation, growth and impacts of the human species worldwide, including all of its written history, technological revolutions, development of major civilizations, and overall significant transition towards urban living in the present. The human impact on modern-era Earth and its ecosystems may be considered of global si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hotspot (geology)
In geology, hotspots (or hot spots) are volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Examples include the Hawaii, Iceland, and Yellowstone hotspots. A hotspot's position on the Earth's surface is independent of tectonic plate boundaries, and so hotspots may create a chain of volcanoes as the plates move above them. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The alternative plate theory is that the mantle source beneath a hotspot is not anomalously hot, rather the crust above is unusually weak or thin, so that lithospheric extension permits the passive rising of melt from shallow depths. Origin The origins of the concept of hotspots lie in the work of J. Tuzo Wilson, who postulated in 1963 that the formation of the Hawaiian Islands resulted from the slow movement of a tecton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ''zōḗ'' (), "life", meaning "ancient life" ). It is the longest of the Phanerozoic eras, lasting from , and is subdivided into six geologic periods (from oldest to youngest): # Cambrian # Ordovician # Silurian # Devonian # Carboniferous # Permian The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era. The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earth's history, known as the Cambrian explosion, in which most modern phyla first appeared. Arthropods, molluscs, fish, amphibians, reptiles, and synapsids all evolved during the Paleozoic. Life began in the ocean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lava Flow
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from . The volcanic rock resulting from subsequent cooling is also often called ''lava''. A lava flow is an outpouring of lava during an effusive eruption. (An explosive eruption, by contrast, produces a mixture of volcanic ash and other fragments called tephra, not lava flows.) The viscosity of most lava is about that of ketchup, roughly 10,000 to 100,000 times that of water. Even so, lava can flow great distances before cooling causes it to solidify, because lava exposed to air quickly develops a solid crust that insulates the remaining liquid lava, helping to keep it hot and inviscid enough to continue flowing. The word ''lava'' comes from Italian and is probably derived from the Latin word ''labes'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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