Originally posted by WiLL
why would it explode?
if the thing hits the earth. the people living where the collision will have headaches for a while. 
h: then fires will start. the vibrations will be that of many huge earthquakes. dust will start to arise, covering the sky starting years of darkness. plants will die...and then the dinosaurs will also.
Yellow stone national park is the largest volcano. Years back it did erupt and statistics show a sudden decline in the population. Its scary because its a tourist hot spot and yet deep down below its slowing starting to work towards an eruption.