[SunkenCiv]

from another file, a post by "Owen" (didn't check this):

There's also an impact crater buried under eastern Antarctica. The crater is about the size of the state of Ohio, and the asteroid that caused it was probably 30 miles wide. That event also dates from the P/T boundary. Either of them would have been hefty enough to cause worldwide climatic instability lasting for milennia, not to mention the initial cascade of firestorms resulting from ejecta falling bath onto Earth. And the locations of both creaters might have been sufficent to give the opposite side of the world (Siberia at that time) a hefty boot from below. Any putative Siberian magma chambers existing then could conceivable have moved closer to the surface and/or actually broken out, yielding the Siberian Traps as we know them.

[SunkenCiv]

Old-style topic, I had it saved into a file; refers to Devonian impact:

• New Crater Found Down Under