tektite
tek·tite
T0085600 (tĕk′tīt′)tektite
(ˈtɛktaɪt)tek•tite
(ˈtɛk taɪt)n.
tek·tite
(tĕk′tīt′)| Noun | 1. | tektite - thought to derive from meteorites |
| 单词 | tektite | |||
| 释义 | tektitetek·titeT0085600 (tĕk′tīt′)tektite(ˈtɛktaɪt)tek•tite(ˈtɛk taɪt)n. tek·tite(tĕk′tīt′)
tektitetektite(tĕktīt), naturally occurring, silica-rich (65%–80% SiO2) glass resembling obsidian and sometimes shale, and is normally jet black to olive green. They appear as small rounded or elongated objects that often have aerodynamic shapes and range from a fraction of an ounce to several pounds in weight. They are found in limited areas on the earth's surface called strewn fields (in contrast to meteorites, which show a random distribution over the whole earth). Tektites, originally named by Eduard SuessSuess, Eduard, 1831–1914, Austrian geologist, b. London. He was a professor (1857–1901) at the Univ. of Vienna and served for more than 20 years in the Austrian parliament. ..... Click the link for more information. are usually given a name derived from the region in which they are found; moldavites (from the Vlatava, or Moldau, River in the Czech Republic), bediasites (from the territory of the Bedias Native Americans in Texas), indochinites, philippinites, australites, javanites, and Côte d'Ivoire tektites are the principal groups. Their peculiar composition, physical characteristics, and restricted geographic distribution gave rise to several theories: one suggests a lunar origin, i.e., that they were the result of a lunar meteorite impact that ejected splashes of molten lunar rock, some of which eventually made their way to earth; however, the composition of moon rocks does not resemble tektites, and the lunar-origin theory, for the most part, is questionable. Another theory suggests their origin to be through the fusion and ejection of terrestrial material by the impact of giant meteorites or comets on the earth; the moldavites and the Côte d'Ivoire tektites have been linked with such impacts, but the source of the remaining tektite groups is still uncertain. Tektitea collective term for objects of natural glass that are green, yellow, or black in color, that are wholly fused, and that possess various shapes and dimensions and a characteristic surface sculpture. Tektites may contain up to 88.5 percent SiO2, 20.5 percent Al2O3, 11.5 percent FeO, and 8.5 percent CaO; the presence of Ni and the low content of water compared with other glasses are important features. Tektites have no magnetization. The term “tektite” was introduced by the Austrian geologist F. E. Suess in 1900. Numerous legends circulated among ancient peoples concerning tektites, which were used in healing and as amulets. Tektites have been found on all the continents except Antarctica. Tektites are often named after the place where they are found. Irgizites and zhamanshinites are named for the Irgiz River and the Zhamanshin area in the Southern Urals, respectively. Moldavites take their name from the Moldau River, now called the Vltava, in Czechoslovakia. Philippinites were discovered in the Philippines, indochinites in Indochina, and australites in Australia. Tektites are found only in Paleogene-Anthropogenic beds or simply on the earth’s surface in areas that preclude the possibility of volcanic origin. There is as yet no generally accepted hypothesis concerning the origin of tektites. While some consider tektites to be meteorites, others suggest that tektites were formed as a result of the impact of meteorites, asteroids, or comets. Studies on tektites in the 1960’s and 1970’s at the Zhamanshin area in the USSR support the idea that Zhamanshin’s ring structure originated from the impact of a meteorite and that tektites were formed primarily from terrestrial matter through a remelting process occasioned by high temperatures (impact metamorphism). REFERENCEVorob’ev, G. G. Chto vy znaete o tektitakh. Moscow, 1966.T. A. GRETSKAIA tektite[′tek‚tīt]tektite
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