Eltanin
The only known impact of a large asteroid into the deep ocean.
Key facts
- When
- about 2.5 million years ago
- Where
- Bellingshausen Sea, south-eastern Pacific Ocean
- What hit
- an asteroid probably about 1 to 2 km across
- Era
- Deep time
- Location
- 57.80° S, 90.80° W
Very roughly a hundred thousand to a million megatons of TNT.
Similar to or larger than the Ries impact, but into water about 5 km deep.
What happened
Most impact craters are found on land, but about 70 per cent of Earth's surface is ocean. Eltanin is the one well-studied case of a large asteroid striking deep water.
It was discovered in 1981, when scientists found unusually high levels of iridium in sediment cores collected in the 1960s by the research ship Eltanin, between South America and Antarctica. Later expeditions in 1995 and 2001 collected more cores, which contain broken meteorite fragments and melted droplets mixed with jumbled sea-floor sediment.
There is no crater. The water was so deep that the asteroid did not reach the sea floor with full force; most of its energy went into the ocean.
Effects
Computer models suggest the impact threw up a curtain of water several kilometres high and launched enormous waves across the Pacific and Southern Oceans, which would have struck the coasts of South America and Antarctica. Rocks in Antarctica and Chile have been examined for signs of such a tsunami, but firm evidence is hard to find.
The evidence
The iridium anomaly, meteoritic debris in the sediment cores, and a disturbed layer of sea-floor sediment spread over a large area.
Did you know?
Eltanin happened at about the time the great ice ages of the northern hemisphere were beginning, but no link between the two has been shown.
Without cores taken for other reasons decades earlier, this impact might never have been found.
Related pages
How is impact energy measured? See energy explained, or try the impact calculator.