fred:

Check out the historic volcanic activity at this site:

http://volcanic-eruptions.findthedata.org/

I found it to be quite interesting. The list includes 617 eruptions rated from 'non-explosive' to 'colossal' in our recent geological history. It seems to me that there is a continual 'zitfest' going on.

The scariest one for us in western North America, & perhaps even farther, is the sleeping giant, Yellowstone's Super Volcano, WY.

http://www.foxnews.com/scitech/2011/04/13/yellowstones-supervolcano-surprisingly-humongous/

It is surmised that it may blow its top again sometime; however, for much of North America, climate change will be the least of our worries...

TAM