I found a cool web site about dry ice:
http://www.dryiceinfo.com
Here is a quote:
...A fantastic simulated volcano can be made in a sink with a garbage disposal. Run hot water and put one to two pound pieces Dry Ice into your garbage disposal. When you turn the disposal on it will make a marvelous eruption. Be sure to wear goggles as the hot water and ejected Dry Ice could be dangerous...