31.Omine Volcano Geosite
Feel the large lava flow and active fault
About 90,000 years ago, huge eruption occurred in Aso (Aso-4). This eruption covered most Kyushu with pyroclastic flow, and covered whole Japan with ash. Just before this huge eruption, Omine Volcano was formed in the west of the caldera. It consists of Omine Pyroclastic Cone and Takayubaru lava spilled from this cone. Futagawa Fault is located at the southern margin of this lava plateau. We can identify a vertical displacement and inclination of lava plateau formed by repeated earthquakes. Today this plateau serves as the Aso Kumamoto Airport.
Fig.1 Omine Volcano erupted in the west of the Aso Caldera. Enormous amount of lava flowed down to the west. This volcano is located just on the Futagawa Fault running to the southwest direction via Mashiki-town from Tateno district in the western margin of Aso Caldera. A similar volcano, Akai Volcano is also formed near from the point of intersection with Futagawa Fault and Hinagu Fault.
(after Watanabe et al., 1979)
Fig. 2 We are looking at Aso Caldera from the west. The caldera wall was destroyed by the repeated earthquakes in Futagawa Fault, and Shirakawa River is flowing through this valley. Omine Volcano erupted west of the caldera, and huge lava flowed to the west. We can see many central cones within the caldera.
Fig. 3 Omine Volcano and Futagawa Fault viewed from the east side.
Fig. 4 The eruption of Omine
Volcano formed Omine Pyroclastic Cone (409m high), and vast lava plateau (Takayubaru Plateau) about 100 m thick, 9 km east-west and 4 km north-south. Repeated large earthquakes (once per thousands of years) occurred in Futagawa Fault formed a vertical displacement about 100 m, and the lava plateau inclines toward the south a little. Today the plateau serves as the Aso Kumamoto Airport.
Fig. 5 The tip of the Takayubaru Lava. We can see the situation which lava flow stops. Flat part was using for the airport and the tip area was used for golf course.
