This style of convergence forces the subducting plates into the athenosphere generating friction. The partially molten athenosphere and the solid ocean crust become completely molten in areas and that molten material rises to the surface of the ocean crust. The molten material cools as it rises, creating islands. Since converging plates and not hot spots, like Hawaii, create these islands they should continue building as long as the plates move in this fashion.
In the case of Japan, the subduction zone allows for an abundance of active volcanos. Beppu as well as Mount Aso, an active composite volcano, reside on Kyushu. Mt. Aso is not a single peak, but actually composed of Mt. Taka, Mt. Naka, Mt. Eboshi, Mt. Kijima, and Mt. Neko. Pyroclastic flows from four different explosions supposedly formed each peak- the oldest about 270,000 years ago (“Description”). To this day, the crater of Mt. Naka continues realeasing volcanic ash made of incredibly tiny pyroclastics, also known as tephra.
One of the world's largest calderas, measuring 11x15 miles, surrounds the five peaks (“Mt. Aso”). Although a composite volcano like Mt. Aso encourages explosive eruptions, this caldera formed nonexplosively. Instead of volcanos collapsing in on themselves after erupting, this area of the continental plate "floated" on chambers of molten material. When the volcanos contained in the area exploded, the magma released from the underground chambers causing the structure to fall. A vast expanse of fertile land capable of sustaining over 50,000 people remained ("Mt. Aso).
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| Mt. Naka Crater |
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| Mt. Aso Caldera |
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| Mt. Aso Caldera Basin |
Sources:
“Description of Mt. Aso.” Information on Restrictions for the Aso Volcano West Crater.
Web. The Aso Volcano Disaster Prevention Council, 2008. Web. 9 February.
2012.
“Mt. Aso.” Japan Atlas: Nature. Web Japan. Web. 9 February. 2012.
Images Courtesy of (in order of appearance):
-http://www.japan-hopper.com/2007/10/30_061262.php
-http://mynxbrom.blogspot.com/2011/07/kyushu-spring-break-adventure.html
-http://www.houseofjapan.com/travel/a-visit-to-mount-aso
I had the pleasure of exploring this area several years ago while staying in Fukuoka, and in may aspects, driving around is like driving around Kansas except on the wring side of the road. I didn't realise that Mt. Aso is actually comprised of several peaks, or that its caldera stretches on for so long. Good to know there is still volcanic activity happening on Kyushuu! I wonder what effect that ash has had on the people in that area.
ReplyDeleteYour blog has a great amount of information about the formation of Japan. It is interesting to me how Japan was formed by subducting plates. I have known that Japan has many earthquakes but I was never really know why until now. I have experienced the useful of dry magma from the volcano in my country Vietnam. The soil is very rich in minerals and nutrition so it is very good to use for agriculture.Before when it comes to Japan, I only know about its famous cherry blossom but thanks to your blog that now I know more about Japan's formation and mountains.
ReplyDeleteTram Vo