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Description of Mt. Aso

Overview of Mt. Aso

 Located in the Aso area of Kumamoto Prefecture in the center of Kyushu, this is one of the largest calderas in the world. It is 17 kilometers across from east to west, 25 kilometers across from north to south, and has an area of roughly 350 square kilometers. The central crater group, which includes the still active Mt. Naka, incorporates the five Aso peaks.
central crater group is referred to as Mt. Aso.
The five Aso peaks are Mt. Taka, Mt. Naka, Mt. Eboshi, Mt. Kijima, and Mt. Neko. There is no single Mt. Aso.
In addition, the so-called outer mountains were formed from the pyroclastic flows on the outside of the caldera. From an academic perspective, these outer mountains are considered a part of the Aso volcano.

The composition of the site

 It is thought that the current Mt. Aso was created by four large eruptions in the ancient past.
These occurred about 270,000 years ago, about 140,000 years ago, about 120,000 years ago, and about 90,000 years ago. The last eruption about 90,000 years ago was particularly large, The deposits generated by the pyroclastic flows from that eruption have been confirmed to have traveled across the sea to Shimabara, Amakusa, and Yamaguchi Prefecture.
The most distant location of these deposits has been confirmed to be Akiyoshidai in Yamaguchi Prefecture. Deposits of volcanic ash from this eruption more than 10 centimeters deep still remain in the eastern part of Hokkaido.
This volcanic activity spewed an enormous amount of underground magma to the surface. This created a large underground space that resulted in the collapse of the ground. That is thought to be the reason the large caldera in Aso was created.
After the formation of the caldera about 70,000 years ago, the central crater group was created in its center. Today, the five peaks that make up Mt. Aso are arrayed in the center of this large caldera.

What is a caldera?

  A caldera is a circular depression in the earth that is larger than an ordinary crater.
Generally speaking, most craters do not exceed one kilometer, but a caldera is much larger than that.
A caldera is distinguished from a crater because the large depression is not thought to have been created by a simple eruption or explosion.
There are three types of calderas classified by the way in which they were created: explosive, non-explosive, and non-volcanic. The Aso caldera, which extends 17 kilometers from east to west and 25 kilometers from north to south, is a non-explosive caldera. It is one of the largest calderas in the world, roughly equal in size to the Aira caldera.
The word caldera is derived from the Portuguese word for cauldron.