I live not too far from the Danish location Stevn Klint, a chalk cliff formation where the Alvarez'es found one very neat exhibit for their case. Utterly fascinating: You can climb to the foot of the cliffs, and there, unmistakable and obvious, is the dark, horizontal line in the massive wall of white - you can see it, you can touch it, and you can ponder the very different nature of fossil below and above the line.

There is a local museum rigth next to the cliffs. A few years ago, I spoke to the leader there, a woman with a ph.d. in history, who more or less supplied the final death blow to any lingering respect I might have held for any kind of humanities: Her only take on Walter and Louis Alvarez and their world famous work in her own backyard was how of course they were so arrogant, they had raised hostility among scientists and everybody else the world over.

what's that to do with anything in the thread

Arrogant about what?

I took it to be a humanities view of being out of whack with concensus.

> Could the volcanic activity be triggered by comets?

That's an interesting question. My completely unqualified opinion would be no, an comet couldn't trigger the massive and ongoing volcanic activity that a mass extinction requires. I'd like to hear from someone more informed though.

Could a big enough comet impact cause the Earth behave like a liquid and therefore a wave destabilize the crust and increase volcanic events?