Asteroid impacts.

matthyaouw

I've been wondering- what would happen to an asteroid striking the deep ocean? On land they leave fairly massive craters, but at sea, would there be an impact crater on the floor, or would the resistance of the water reduce the asteroid to a fine sediment before it could impact with the bottom?

Andre

I have seen a banana, shot by an compressed air cannon going right though a wooden panel. So breaking up would not change the sum of the tremendous inertia momentum of the parts. This may be too high to slow it down significantly.

Evo

This isn't much

"More recent prehistoric impacts are theorized (Ancient Crash, Epic Wave by Sandra Blakeslee, New York Times, 14 Nov 2006) by the Holocene Impact Working Group, including Dallas Abbott of Lamont-Doherty Earth Observatory in Palisades, N.Y. This group points to four enormous chevron sediment deposits at the southern end of Madagascar, containing deep-ocean microfossils fused with metals typically formed by cosmic impacts. All of the chevrons point toward a spot in the middle of the Indian Ocean where a newly discovered crater, 18 miles in diameter, lies 12,500 feet below the surface. This group posits that a large asteroid or comet impact 4,500--5,000 years ago, produced a mega-tsunami at least 600 feet high. If this and other recent impacts prove correct, the rate of asteroid impacts is much higher than currently thought."

http://en.wikipedia.org/wiki/Impact_event

Andrew Mason

Given that a chunk of the Canary Islands (of about 20 cubic kilometres in volume or about 3000 m x 3000 m x 2200 m) falling into the Atlantic would, it is predicted (by some), cause a massive 200 foot tidal wave on the US east cost, an asteroid of much smaller size hitting the ocean would be a cataclysmic event unlike anything mankind has ever experienced.

AM

matthyaouw

Thanks for the link Evo. I googled submarine impact crater etc. and nothing came up about the deep ocean. I guess i was ignoring the obvious source!

billiards

Obviously it depends on the size of the impactor, one striking feature of the oceans is that the crust is thinner and I believe hotter. Thus an impactor on the ocean is more likely to give rise to large igneous provinces, could the Ontong Java Plateau have been caused by an impact?

Note: this is a controvercial topic right now, for more information visit http://www.mantleplumes.org/OJ_Impact.html

One way to test the hypothesis would be to drill to the base of the layer and see how old it is in relation to the surface rocks, if the age gap were relatively small (a few 100,000 years) it would lend weight to the impact hypothesis, the only problem is you'd need to drill a hole 10-30 km deep!

matthyaouw

Interesting. Thanks for the link! It will come in handy for an essay I'm doing at the moment too

Phobos

Looks like a 1.7 km asteroid (or an object with an expected 30 km crater) will plow right through the deepest ocean and slam into bedrock unhindered. Obviously, smaller asteroids could hit bottom too depending on the location of the strike.

source: Report of the Task Force on potentially hazardous Near Earth Objects. UK. Sept 2000