Late Pleostocene Human Population Bottlenecks. . . (Toba)

The Bradshaw Foundation ^ | 1998 | Stanley H. Ambrose

[blam]

The 10 Biggest Volcanic Eruptions in History

"Uturuncu, the highest peak in SW Bolivia, is surrounded by one of the most dense concentrations of supervolcanoes on the planet, all of which fell silent some 1 million years ago. "

[SunkenCiv]

Anniversary re-ping.

[blam]

"Does the author state what was the largest known eruption?"

Sorry, I wasn't ignoring you...I just came across this year old question.

I don't know. I can't answer the question.

[piasa]

Actually when preparing a stable platform on an arrowhead or knife for percussion flaking you do grind it on a bit of sandstone, especially if the chert is heat treated and a bit brittle.

But it’s true the pictured stone doesn’t look a thing like a grindstone.