Akita-Komagatake

Geography & Climate

Akita-Komagatake is located in Japan, within the Northeast Japan Volcanic Arc of the broader Northwestern Pacific Volcanic Regions. Situated at 39.76° N, 140.80° E in the Northern Hemisphere, the volcano lies within a temperate climate zone. With a summit elevation of 1,637 meters above sea level, Akita-Komagatake is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Akita-Komagatake sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Japan near Akita-Komagatake, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is basalt / picro-basalt, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

Akita-Komagatake has 18 recorded eruptions in the geological database, spanning from 8800 BCE to 1970 CE. The most powerful recorded event was a cataclysmic eruption with ash columns reaching the stratosphere in 7850 BCE, reaching VEI 4 on the Volcanic Explosivity Index. Notable eruptions include 807 CE (VEI 3), 350 BCE (VEI 3), 5950 BCE (VEI 3). This level of eruptive frequency indicates a persistently active volcanic system that warrants ongoing monitoring. The most recent eruption in 1970 CE places this volcano within the modern era of volcanological observation.

Significance

With a maximum recorded VEI of 4, Akita-Komagatake has demonstrated the capacity for significant explosive eruptions that can impact regional aviation, agriculture, and communities tens of kilometers from the summit. VEI 4 eruptions produce ash columns reaching 15-25 kilometers into the atmosphere. With 18 recorded eruptions, Akita-Komagatake has a substantial eruptive history that provides valuable data for understanding volcanic behavior and assessing future hazards in the Northwestern Pacific Volcanic Regions region. Given its recent activity, Akita-Komagatake is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

Two calderas partially filled by basaltic cones cut the summit of Akita-Komagatake volcano. The larger southern caldera is 1.5 x 3 km wide and has a shallow sloping floor that is drained through a narrow gap cutting the SW caldera rim. On its northern side is a smaller more circular 1.2-km-wide caldera whose rim is breached widely to the NE. The two calderas were formed following explosive eruptions at the end of the Pleistocene, between about 13,500 and 11,600 years ago. Two cones, Medake and Kodake, occupy the NE corner of the southern caldera, whose long axis trends NE-SW. The Onamedake cone within the northern caldera has produced lava flows to the north and east; it has a 100-m-wide summit crater. Small-scale historical eruptions have occurred from cones and fissure vents inside the southern caldera. The temperatures of geothermal areas increased beginning in 2005, and some fumarolic plumes were observed in 2011-12.

— Smithsonian Institution, Global Volcanism Program