Latest Issue

2016 Vol.125 No.3

Komezuka Scoria Cone at Aso Volcano

The Komezuka scoria cone (370-380 m in basal diameter; 80 m in height), located in the northwestern part of the post-caldera central cones of Aso Volcano, southwestern Japan, was formed by strombolian eruptions 3300 years ago, and is one of the youngest volcanoes in the Aso caldera. Komezuka, which means rice mound, is named after a legend in which Takeiwatatsunomikoto, the main god of the Aso Shrine, skimmed rice from the mound by hand and distributed it among poor people. The scoria cone is a famous part of the representative landscape of Aso Volcano, because of the beautiful grassed shape of the cone. However, several cracks were formed around the crater rim by the Kumamoto earthquake (Mj 7.3) on April 16, 2016 (arrows of photo taken after the earthquake)． The earthquake triggered many shallow landslides on the slope of the Janoo cinder cone located about 1.5 km west of Komezuka (Fig. 13 of Pictorial 1)． In contrast, the beautiful shape of the Komezuka scoria cone was preserved, although there was a small displacement due to the formation of cracks around the crater rim. The Aso caldera wall, which is called somma, can be seen in the background. The northern caldera wall ranges in height from 300 to 450 m, and has a flattened top because the Aso ignimbrites completely fill topographic lows around the northern caldera rim. Several landslides occurred on steep slopes at the northwestern to western caldera walls due to the 2016 Kumamoto earthquake.

（Photograph & Explanation: Yasuo MIYABUCHI; May 1, 2016）