Minami-Hiyoshi

Geography & Climate

Minami-Hiyoshi is located in Japan, within the Mariana Volcanic Arc of the broader Northwestern Pacific Volcanic Regions. Situated at 23.50° N, 141.94° E in the Northern Hemisphere, the volcano lies within a tropical climate zone. With an elevation of -107 meters — below sea level — Minami-Hiyoshi is a submarine or submerged volcanic feature. Submarine volcanoes make up the majority of Earth's volcanic activity, though most eruptions go unobserved beneath the ocean surface. 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

Minami-Hiyoshi 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 Minami-Hiyoshi, 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 trachyandesite / basaltic trachyandesite, 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

Minami-Hiyoshi has 6 recorded eruptions in the geological database, spanning from 1975 CE to 1996 CE. This eruption frequency indicates a moderately active volcanic system with periodic reawakenings. The most recent eruption in 1996 CE places this volcano within the modern era of volcanological observation.

Significance

With 6 recorded eruptions on file, Minami-Hiyoshi has enough documented activity to help scientists identify patterns in its eruptive behavior. Given its recent activity, Minami-Hiyoshi is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

Periodic water discoloration and water-spouting have been reported over the Minami-Hiyoshi submarine volcano since 1975, when detonation sounds and an explosion were also reported. It lies near the SE end of a coalescing chain of youthful seamounts, and is the only vent with recorded activity. The reported depth of the summit of the trachyandesitic volcano has varied between 274 and 30 m. The morphologically youthful seamounts Kita-Hiyoshi and Naka-Hiyoshi lie to the NW, and Ko-Hiyoshi to the SE.

— Smithsonian Institution, Global Volcanism Program