Whenever I go to Japan, my father-in-law always brings me some place interesting.  He knows that I love earth science, so this year he took me to Mt. Bandai, the scene of a horrific volcanic eruption in 1888.  This was similar to Mt. St. Helens because it was a huge explosion, followed by mud and ash flows.  In the picture below, you can see the missing part of the mountain (lighter brown with missing vegetation).  It used to be a “conical” mountain much like Mt. Fuji.  Because of this, they called it Aizu-Fuji.  After the explosion, it didn’t look like Fuji anymore. 

This type of eruption is called a “phreatic” eruption, meaning the mountain exploded due to pressure from steam supplied from underground magma and/or heated groundwater.  The eruption also produced heated blasts of steam and gases, thickly mixed with ashes and rock fragments.  This is similar to what happened at Mt. St. Helens in 1980.  The 1888 eruption of Mt. Bandai produced a debris avalanche of 2 billion tons and the summit area rapidly collapsed down into nearby rivers to form mudflows which destroyed 5 villages killing many people.   

The mudflows and avalanches dammed up several rivers forming about 300 lakes and ponds.  Today, these lakes and ponds are a popular tourist hiking destination, as the different minerals in each lake give them different colors.  I saw one lake which was a brilliant light blue color that must have had plenty of magnesium in it.

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