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The Eltanin impact was an asteroid impact in the southeast Pacific Ocean at the beginning of the Quaternary Period 2.5 million years ago. The location was at the edge of the Bellingshausen Sea southwest of Chile. The impact was described in 1981. The evidence was collected in 1965 by the research vessel USNS Eltanin (T-AK-270), after which the impact and asteroid are named. Later studies were done by the vessel Polarstern. Sediment at the bottom of the deep ocean in the area had an iridium enrichment, a strong sign of extraterrestrial contamination. Debris from the asteroid is spread over an area of . Sediments from the Eocene and Paleocene were mixed up and deposited again chaotically. Also mixed in were melted and fragmented meteorite matter. The area near the Freeden Seamounts over has a meteorite density of 10–60 kg/m2. Of this, 87% is melted and 13% only fragmented. This is the region of the Earth's surface with the highest density of meteorite material coverage.〔 The disturbed sediment had three layers. The bottommost layer SU IV is a chaotic mixture of broken up sediments in the form of a breccia. Above this is layer SU III consisting of layered sand deposited from turbulently flowing water. Above this is SU II layer with meteorite fragments and graded silt and clay that settled out of still but dirty water.〔 ==Asteroid== The impacting body, the Eltanin asteroid was between in diameter and traveled with a speed of . The size of the asteroid can be calculated by the amount of iridium found in the disturbed sediments. Assuming that there were 187 parts per billion of iridium in the asteroid, the known distribution of the metal leads to estimates that the body was over in diameter. The composition of the meteorites classifies them as low metal mesosiderites. The meteorite explosion also produced microspherules under half a millimeter in diameter. Some of these are glass, and others have spinel and pyroxene. Elements enriched include calcium, aluminium and titanium.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Eltanin impact」の詳細全文を読む スポンサード リンク
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