Ecuador's Tungurahua volcano — "the Black Giant" — is one of the most active volcanos on Earth.  For the last 1300 years, Tungurahua has been nature's version of the bipolar girlfriend.  Beautiful and friendly for awhile, and then  every 80—100 years...boom! The top blows.  Tungurahua's latest foul mood started around 1999, after almost a century of good behavior.