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Eltanin Impact
The Eltanin impact is thought to be an impact event, asteroid impact in the eastern part of the South Pacific Ocean that occurred around the Pliocene-Pleistocene boundary approximately 2.51 ± 0.07 million years ago. The impact occurred at the north edge of the Bellingshausen Sea southwest of Chile, where the sea floor is approximately deep. The asteroid was estimated to be about in diameter. No crater associated with the impact has been discovered. The impact likely evaporated of water, generating large tsunami waves hundreds of metres high. Description The possible impact site was first discovered in 1981 as an iridium anomaly in sediment cores collected by the research vessel ''USNS Eltanin (T-AK-270), Eltanin'', after which the site and impactor are named. Later studies were done by the vessel ''RV Polarstern, Polarstern''. Sediment at the bottom of the deep ocean in the area had an iridium enrichment, a strong sign of extraterrestrial contamination. Possible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek () 'most' and (; Latinized as ) 'new'. The aridification and cooling trends of the preceding Neogene were continued in the Pleistocene. The climate was strongly variable depending on the glacial cycle, oscillating between cold Glacial period, glacial periods and warmer Interglacial, int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinel
Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , a diminutive form of ''spine,'' in reference to its pointed crystals. Properties Spinel crystallizes in the isometric system; common crystal forms are octahedron, octahedra, usually Crystal twinning, twinned. It has no true Cleavage (crystal), cleavage, but shows an octahedral Parting (crystal), parting and a conchoidal fracture. Its Mohs scale of mineral hardness, hardness is 8, its specific gravity is 3.5–4.1, and it is transparent to opaque with a vitreous to dull Lustre (mineralogy), luster. It may be colorless, but is usually various shades of red, lavender (color), lavender, blue, green, brown, black, or yellow. Chromium(III) causes the red color in spinel from Burma. Some spinels are among the most famous gemstones; among them are the Black Prince's Ruby and the "Timur ruby" in the British Crown Jewels ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Albedo
Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects all incident radiation). ''Surface albedo'' is defined as the ratio of Radiosity (radiometry), radiosity ''J''e to the irradiance ''E''e (flux per unit area) received by a surface. The proportion reflected is not only determined by properties of the surface itself, but also by the spectral and angular distribution of solar radiation reaching the Earth's surface. These factors vary with atmospheric composition, geographic location, and time (see position of the Sun). While directional-hemispherical reflectance factor is calculated for a single angle of incidence (i.e., for a given position of the Sun), albedo is the directional integration of reflectance over all solar angles in a given period. The temporal resolution may range from seconds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Acidification
Soil acidification is the buildup of hydrogen cations, which reduces the soil pH. Chemically, this happens when a proton donor gets added to the soil. The donor can be an acid, such as nitric acid, sulfuric acid, or carbonic acid. It can also be a compound such as aluminium sulfate, which reacts in the soil to release protons. Acidification also occurs when base cations such as calcium, magnesium, potassium and sodium are leached from the soil. Soil acidification naturally occurs as lichens and algae begin to break down rock surfaces. Acids continue with this dissolution as soil develops. With time and weathering, soils become more acidic in natural ecosystems. Soil acidification rates can vary, and increase with certain factors such as acid rain, agriculture, and pollution. Causes Acid rain Rainfall is naturally acidic due to carbonic acid forming from carbon dioxide in the atmosphere. This compound causes rainfall pH to be around 5.0–5.5. When rainfall has a lower pH than n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ozone Layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorption (electromagnetic radiation), absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer peaks at 8 to 15 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately above Earth, although its thickness varies seasonally and geographically. The ozone layer was discovered in 1913 by French physicists Charles Fabry and Henri Buisson. Measurements of the sun showed that the radiation sent out from its surface and reaching the ground on Earth is usually consistent with the spectrum of a black body with a temperature in the range of , except that there was no radiation below a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Shelve
An ice shelf is a large platform of glacial ice floating on the ocean, fed by one or multiple tributary glaciers. Ice shelves form along coastlines where the ice thickness is insufficient to displace the more dense surrounding ocean water. The boundary between the ice shelf (floating) and grounded ice (resting on bedrock or sediment) is referred to as the grounding line; the boundary between the ice shelf and the open ocean (often covered by sea ice) is the ice front or calving front. Ice shelves are found in Antarctica and the Arctic (Greenland, Northern Canada, and the Russian Arctic), and can range in thickness from about . The world's largest ice shelves are the Ross Ice Shelf and the Filchner-Ronne Ice Shelf in Antarctica. The movement of ice shelves is principally driven by gravity-induced pressure from the grounded ice. That flow continually moves ice from the grounding line to the seaward front of the shelf. Typically, a shelf front will extend forward for years ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Cap
In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Description By definition, ice caps are not constrained by topographical features (i.e., they must lie over the top of mountains). By contrast, ice masses of similar size that ''are'' constrained by topographical features are known as ice fields. The ''dome'' of an ice cap is usually centred on the highest point of a massif. Ice flows away from this high point (the ice divide) towards the ice cap's periphery. Ice caps significantly affect the geomorphology of the area they occupy. Plastic moulding, gouging and other glacial erosional features become present upon the glacier's retreat. Many lakes, such as the Great Lakes in North America, as well as numerous valleys have been formed by glacial action over hundreds of thousands of years. The Antarctic and Greenland contain 99% of the ice volume on earth, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiji
Fiji, officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about 110 are permanently inhabited—and more than 500 islets, amounting to a total land area of about . The most outlying island group is Ono-i-Lau. About 87% of the total population live on the two major islands, Viti Levu and Vanua Levu. About three-quarters of Fijians live on Viti Levu's coasts, either in the capital city of Suva, or in smaller urban centres such as Nadi (where tourism is the major local industry) or Lautoka (where the Sugarcane, sugar-cane industry is dominant). The interior of Viti Levu is sparsely inhabited because of its terrain. The majority of Fiji's islands were formed by Volcano, volcanic activity starting around 150 million years ago. Some geothermal activity still occurs today on the islands of Vanua Levu and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tasmania
Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The state encompasses the main island of Tasmania, the List of islands by area#Islands, 26th-largest island in the world, and the List of islands of Tasmania, surrounding 1000 islands. It is Australia's smallest and least populous state, with 573,479 residents . The List of Australian capital cities, state capital and largest city is Hobart, with around 40% of the population living in the Greater Hobart area. Estimated resident population, 30 June 2017. Tasmania is the most decentralised state in Australia, with the lowest proportion of its residents living within its capital city. Tasmania's main island was first inhabited by Aboriginal Australians, Aboriginal peoples, who today generally identify as Palawa or Pakana. It is believed that Abori ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctic Peninsula
The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martin in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctica. The Antarctic Peninsula is part of the larger peninsula of West Antarctica, protruding from a line between Cape Adams (Weddell Sea) and a point on the mainland south of the Eklund Islands. Beneath the ice sheet that covers it, the Antarctic Peninsula consists of a string of bedrock islands; these are separated by deep channels whose bottoms lie at depths considerably below current sea level. They are joined by a grounded ice sheet. Tierra del Fuego, the southernmost tip of South America, is about away across the Drake Passage. The Antarctic Peninsula is in area and 80% ice-covered. The marine ecosystem around the western continental shelf of the Antarctic Peninsula (WAP) has been subjected to rapid Climate change in Antarctica, clima ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erosion Surface
In geology and geomorphology, an erosion surface is a surface of rock (geology), rock or regolith that was formed by erosion and not by construction (e.g. lava flows, sediment deposition) nor fault (geology), fault displacement. Erosional surfaces within the Lithostratigraphy#Stratigraphic relationship, stratigraphic record are known as unconformity, unconformities, but not all unconformities are buried erosion surfaces. Erosion surfaces vary in scale and can be formed on a mountain range or a rock. Particularly large and flat erosion surfaces receive the names of peneplain, wikt:paleoplain, paleoplain, planation surface or pediplain. An example of erosion surface is road surface erosion which is caused by natural and anthropogenic factors. Erosion surface can be measured through direct, contact measurement methods and indirect, non-contact measurement methods. Road surface erosion Just like mountains and rocks, erosion can also occur on unsealed roads due to natural and Human im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanium
Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in sea water, aqua regia, and chlorine. Titanium was discovered in Cornwall, Great Britain, by William Gregor in 1791 and was named by Martin Heinrich Klaproth after the Titans of Greek mythology. The element occurs within a number of minerals, principally rutile and ilmenite, which are widely distributed in the Earth's crust and lithosphere; it is found in almost all living things, as well as bodies of water, rocks, and soils. The metal is extracted from its principal mineral ores by the Kroll and Hunter processes. The most common compound, titanium dioxide (TiO2), is a popular photocatalyst and is used in the manufacture of white pigments. Other compounds include titanium tetrachloride (TiCl4), a component of smoke screens and cata ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
