Ancient Crash, Epic Wave

avtchillsboro writes "A NY Times article says that scientists have discovered evidence a massive impact crater 18 miles in diameter and 12,500 feet under the Indian Ocean. The evidence, they say, consists of four massive chevron-shaped sediment deposits on the island of Madagascar. 'Each covers twice the area of Manhattan with sediment as deep as the Chrysler Building is high. On close inspection, the chevron deposits contain deep ocean microfossils that are fused with a medley of metals typically formed by cosmic impacts. And all of them point in the same direction — toward the middle of the Indian Ocean where a newly discovered crater, 18 miles in diameter, lies 12,500 feet below the surface.' Interestingly, the scientists say that the currently accepted notion that there have been no major impacts in the last 10,000 years is wrong; and that major impacts occur on average every 1,000 years, rather than the currently accepted 500,000 to 1,000,000 year interval. '(T)he self-described "band of misfits" that make up the two-year-old Holocene Impact Working Group say that astronomers simply have not known how or where to look for evidence of such impacts along the world's shorelines and in the deep ocean.'"

Comments

I thought it sounded familiar

[smooth wombat]

And then I realized, it's from 6 days ago when I posted the exact same story in my journal. On top of which I had also checked it off to be a possible story and the editors of course rejected it.

Slashdot, where the news is stale, the editors don't edit and geeks still can't get a girlfriend.

Re:Written history

[Anonymous Coward]

4,800 years ago would be Pre-dynastic Eygpt, so it'd be better looking elsewhere, maybe mesopotamia?

Re:Written history

[dreamchaser]

You mean like the Great Flood stories shared by most ancient civilizations?

Interesting research, but ...

[Mostly a lurker]

... I find it difficult to understand how failure to account before for ocean impacts of meteors could change the anticipated frequency of large meteor impacts from once every 500,000-1,000,000 years to once every 1,000. Surely, a frequency of once every 1,000 years or so would mean several hundred hitting land every million years. Those would, one imagines, leave pretty obvious evidence.

Re:Interesting methods, troubling results

[zeropointburn]

I stand corrected.
You're absolutely right: a 10-megaton impact would be quite surviveable for the majority of humans. Certainly locally catastrophic, but bomb shelters and the like would be useful down to some distance from impact (based on size, density, velocity, and material at impact, as well as shelter design). I did specify 'large impact', but it was in the context of the article, so that would equate to about 10 megatons.
This would help explain how they came up with the 1,000 year per impact number as opposed to the .5 million year per impact number. Their definition of 'major' apparently differs... of course, it may be that they can find evidence from much smaller impacts underwater due to this gravitational scanning technology than are observable on land after x thousands of years of erosion. Since smaller impacts presumably happen more often, that would make the rate of 10-megaton impacts much faster than that of 1,000 megaton impacts, for instance.