Wednesday, November 15, 2006
Asteroid and Comet Strikes
The NY Times has a great piece on an ongoing project that is reviewing the world's shorelines for "chevron" deposits. The article decsribes some found in Madagascar like this:
"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.
The explanation is obvious to some scientists. A large asteroid or comet, the kind that could kill a quarter of the world’s population, smashed into the Indian Ocean 4,800 years ago, producing a tsunami at least 600 feet high, about 13 times as big as the one that inundated Indonesia nearly two years ago. The wave carried the huge deposits of sediment to land. "
The graphic I borrowed maps known major craters and chevron deposits world-wide. It sort of shrank when I pasted it. Take a good look at the original. We've been hit a lot in the past.