What Mr. Mimatsu Saw

What Mr. Mimatsu Saw and Other Information About Volcanoes

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     In 1943, there was a mailman named Mr. Mimatsu who lived in Japan.  He was looking out the window at his workplace and saw a volcano forming in a potato field.  He saw steam, ash, and lava burst out of the ground.  This was the beginning of a new volcano. 

     Mr. Mimatsu thought that he should keep track of how this volcano grew.  He was looking at it through a window that had wire mesh  in it.  The window looked like graph paper.  

     He got an idea.  He decided to show how much the volcano was growing by recording it on graph paper.  Each month he made a new line on the graph paper to show how much taller the volcano was.  

     This volcano became known as the Showa Shinzan Volcano.

     Showa Shinzan volcano is an example of a dome volcano.  These volcanoes grow slowly as lava flows gently from under the earth's crust.

     Today, Showa Shinzan volcano is 1,320 feet tall and still growing.  

     Some volcanoes, like the one that Mr. Mimatsu saw, change slowly over a long period of time.  However, the Krakatau volcano eruption in 1883 was just the opposite.  

     At first there were several small eruptions on the island.  Then suddenly there was a very violent eruption.  This eruption was violent because Mount Krakatau was over a subduction zone.  

     During this eruption, this 2,620 foot tall volcano blew away and more than half of the island was gone!  

     When the Krakatau volcano blew away, all that was left was a big hole in the ocean floor called a caldera . 

     The big eruption also created a tsunami , a giant wave, that killed about 40,000 people.  

There are different kinds of volcanoes.  Two examples are hot spot volcanoes and mid-ocean ridge volcanoes.  They are formed in different ways.

     Hot spot volcanoes  form when a hot spot, or area of active magma, pushes up through a plate  to create a slow-growing, easy-flowing volcano. 

      Over time, the plate over the hot spot moves.  That first volcano becomes extinct  because the active area of magma (hot spot) is gone. 

     However, a new volcano can now form over the hot spot and will be active until the plate moves it away from the hot spot. 

     After a while, there can be a chain of volcanoes.  The only active one will be the one over the hot spot.   

     Mid-ocean ridge volcanoes form when two plates move away from each other at the center of the oceans.  They form along the mid-ocean ridge, which is one large ridge system that is part of every ocean on earth. 

     This leaves a gap where magma can move up and create many small volcanoes. 

     These volcanoes are always active and actually create new ocean floor.  They can erupt violently creating earthquakes and tsunamis.

Now you know more about volcanoes than you did before you read this book.  

The earth is always changing and volcanoes are one example of how these changes happen.