[DJtex]

One of these super-volcanos erupts on average every 50,000 years or so. Any of them will end civilization, either Toba, or Yellowstone, or Mammoth Mountain in California, or dozens of others.

At 50k years vs. 20 million for an asteriod to hit, this threat is 400 times as likely to end the good times. Also, of course, we're in one of the brief inter-glaciation stages in the Ice Ages that have dominated the earth for 1 to 3 million years. (Eight in the last 750k years). We just don't know how lucky we've been or how tenuous civilization is.

[AntiGuv]

There are twelve more or less 'confirmed' supervolcanos worldwide: four in the lower 48 (WY, CA, OR, NM); one in Alaska; two in Japan; and one each in Indonesia, Italy, New Zealand, Australia, and Ecuador. There's also evidence of possible supervolcanos beneath Guatemala, Vanuatu (in the South Pacific), the Philippines, Papua New Guinea, and under Loch Ness in Scotland.

[Steve Eisenberg]

One of these super-volcanos erupts on average every 50,000 years or so. Any of them will end civilization, either Toba, or Yellowstone, or Mammoth Mountain in California, or dozens of others.

End civilization? What they will do is lower temperatures a fair amount for a couple years. If we have a couple years worth of rice and wheat saved up, civilization should barely burp except in the area of the volcano.