Fukutoku-Oka-no-Ba

Geography & Climate

Fukutoku-Oka-no-Ba is located in Japan, within the Ogasawara Volcanic Arc of the broader Northwestern Pacific Volcanic Regions. Situated at 24.29° N, 141.48° E in the Northern Hemisphere, the volcano lies within a subtropical climate zone. With an elevation of -29 meters — below sea level — Fukutoku-Oka-no-Ba 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

Fukutoku-Oka-no-Ba 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 Fukutoku-Oka-no-Ba, 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

Fukutoku-Oka-no-Ba has 38 recorded eruptions in the geological database, spanning from 1904 CE to 2021 CE. The most powerful recorded event was a cataclysmic eruption with ash columns reaching the stratosphere in 2021 CE, reaching VEI 4 on the Volcanic Explosivity Index. Notable eruptions include 2021 CE (VEI 4), 1914 CE (VEI 3), 1904 CE (VEI 3). With an average interval of roughly 3 years between eruptions over a span of 117 years, this is one of the more frequently active volcanoes in the database. This persistent activity suggests a robust and well-supplied magma system beneath the volcano. With eruptive activity as recently as 2021 CE, Fukutoku-Oka-no-Ba remains an actively monitored volcano.

Significance

With a maximum recorded VEI of 4, Fukutoku-Oka-no-Ba 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. Its 38 recorded eruptions make it one of the most prolific volcanoes in our database, reflecting a persistent and well-documented eruptive history that has provided volcanologists with extensive data for understanding eruption patterns and forecasting future activity. Given its recent activity, Fukutoku-Oka-no-Ba is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

Fukutoku-Oka-no-ba is a submarine volcano located 5 km NE of the island of Minami-Ioto. Water discoloration is frequently observed, and several ephemeral islands have formed in the 20th century. The first of these formed Shin-Ioto ("New Sulfur Island") in 1904, and the most recent island was formed in 1986. The volcano is part of an elongated edifice with two major topographic highs trending NNW-SSE, and is a trachyandesitic volcano geochemically similar to Ioto.

— Smithsonian Institution, Global Volcanism Program