The Eltanin impact is thought to be an

asteroid impact An impact event is a collision between astronomical objects causing measurable effects. Impact events have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effe ...

in the eastern part of the

South Pacific Ocean South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both west and east. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþa ...

that occurred around the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene 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 fin ...

boundary approximately 2.51 ± 0.07 million years ago. The impact occurred at the north edge of the Bellingshausen Sea southwest of

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

, 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 A tsunami ( ; from , ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and underwater explosions (including detonations, ...

waves hundreds of metres high.

Description

The possible impact site was first discovered in 1981 as an

iridium Iridium is a chemical element; it has the symbol Ir and atomic number 77. This very hard, brittle, silvery-white transition metal of the platinum group, is considered the second-densest naturally occurring metal (after osmium) with a density ...

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 The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

and

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

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 Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...

. Above this is layer SU III consisting of layered sand, consistent with having been deposited from turbulently flowing water. Above this is SU II layer with meteorite fragments and graded silt and clay that plausibly 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 In science and engineering, the parts-per notation is a set of pseudo-units to describe the small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measur ...

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 suspected asteroid remnants has been classified as low metal

mesosiderite Mesosiderites are a class of stony–iron meteorites consisting of about equal parts of metallic nickel-iron and silicate. They are breccias with an irregular texture; silicates and metal occur often in lumps or pebbles as well as in fine-grained ...

s. The bolide explosion would also have produced microspherules under half a millimeter in diameter. Some of these are glass, and others have

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. Prop ...

and

pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...

. Elements enriched include

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

and

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 ...

Tsunami

On the shorelines of the Pacific Ocean there are erosional features that are indicative of a very large

. 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 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. ...

. After ten hours, waves around would reach

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 sta ...

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 ...

and Central America, and the New Zealand east 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.

Ice age trigger

At the time of the impact in the

Late Pliocene Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * Late (The 77s album), ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudo ...

, the Earth was cooling. The impact and disruption to the weather could have triggered the start of

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 topogra ...

formation in the Northern Hemisphere. The impact would have put a large amount of water and salt into the atmosphere, disrupted ice shelves, depleted the

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 a ...

, caused surface acidification, and increased the Earth's

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 ...

References

External links