Krakatoa

This is what the volcano Krakatoa looked like before it exploded in August 1883:

This is what it looks like now, the three islands forming what used to be the perimeter of the pre-1883 volcano:

36,000 people died from this eruption--35,000 of them due to the tsunamis. Water was not the only thing moved by the explosion.  Air was moved as well.  Airborne shock waves, measured as atmospheric pressure spikes by rich-ass victorians on their barographs, traveled around the earth seven times!

People on Rodrigues islands heard the explosion, 3000 miles away, which to this day represents the longest distance over which an unamplified natural sound has been detected by the human ear.

Here is a google map of that distance (Krakatoa is on the right):

The eruption was responsible for lowering the temperature by around 1 degree Fahrenheit across the entire globe (on average, for the year following the eruption). In the immediate vicinity of the eruption, temperatures were lowered by 15 degrees Fahrenheit. These effects are due mainly to the dust and sulfuric acid that were spewed into the upper atmosphere, lowering the radiation that hit the earth's surface and making for awesome sunsets.

Most of this information was found in the book "Krakatoa - the day the world exploded" by Simon Winchester, one of my favorite non-fiction authors.

Here is a sweet picture of lava: