The Eltanin impact is thought to be an asteroid impact in the eastern part of the South Pacific Ocean during the Pliocene-Pleistocene boundary around 2.51 ± 0.07 million years ago. The location was at the edge of the Bellingshausen Sea southwest of Chile. The asteroid was estimated to be about in diameter and the impact would have left a crater approximately across.
Description
The possible impact site was first discovered in 1981 as an iridium anomaly in sediment cores collected by the research vessel Eltanin, after which the site and impactor 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. Possible debris from the asteroid is spread over an area of. Sediments from the Eocene and Paleocene were jumbled and deposited again chaotically. Also mixed in were melted and fragmented meteorite matter. The area near the Freeden Seamounts over has a meteorite material surface density of. Of this, 87% is melted and 13% only fragmented. This area is the region of the Earth's surface with the highest known density of meteorite material coverage. The disturbed sediment had three layers. The lowermost layer SU IV is a chaotic mixture of crumbled 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 supposed impacting body, the Eltanin asteroid, is estimated to have been between in diameter and traveling with a speed of. The possible size of the asteroid was 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 size. Based on a diameter of one km, it is estimated it would have left a crater about across. The composition of the meteorites classifies them as low metal mesosiderites. The meteorite explosion would also have 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.
Tsunami
On the shorelines of the Pacific Ocean there are erosional features that are indicative of a very large tsunami. These include an erosional surface and chaotic deposits of mixed terrestrial and ocean-derived sediment. Boulders as big as buses are mixed with marine fossils and mud. The most well-characterised tsunami deposits are near the coast of Chile. Off the coast of Antarctica there are mudslides into the deep ocean from this age. The size of a possible tsunami has been calculated. An asteroid that was in diameter falling onto the deep ocean would have blasted the water off the ocean floor for at least, and made a wave over high on the southern end of Chile and the Antarctic Peninsula. After ten hours, waves around would reach Tasmania, Fiji and Central America, and the New Zealandeast coast would have been washed with high waves. If the impact object was in diameter, the wave heights would have been one-fifth as great.
