Maruyama

Geography & Climate

Maruyama is located in Japan, within the Kuril Volcanic Arc of the broader Northwestern Pacific Volcanic Regions. Situated at 43.42° N, 143.03° E in the Northern Hemisphere, the volcano lies within a temperate climate zone. At 2,013 meters above sea level, Maruyama rises above the surrounding terrain into montane or subalpine conditions. The elevation creates distinct ecological zones along its flanks, from forested lower slopes to exposed rocky terrain near the summit. 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

Maruyama 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 Maruyama, 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 andesite / basaltic andesite, 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

Maruyama has 2 recorded eruptions in the geological database, spanning from 1700 BCE to 1898 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1898 CE, reaching VEI 2 on the Volcanic Explosivity Index. These eruptions span roughly 3,598 years of volcanic history.

GVP Reference Summary

The Nipesotsu-Maruyama volcano group, located west of Nukabira Lake about 20 km E of Tokachidake volcano, is composed of a number of overlapping andesitic-to-rhyolitic stratovolcanoes and lava domes constructed along a NW-SE trend. These volcanoes overlap the SW rim and SW caldera floor of the Pleistocene Tokachimitsumata caldera. The highest peak in the complex is Nipesotsuyama stratovolcano, which was active during the mid-Pleistocene, about 0.4-0.2 million years ago. The Maruyama stratovolcano and lava dome at the southern end of the complex was discovered to be a Quaternary volcano only in 1989. It is also referred to as Higashi-Tokachi-Maruyama to distinguish it from several other volcanoes named Maruyama, which means "Round Mountain." A minor phreatic eruption took place at the Maruyama lava dome in 1898, and fumaroles are present on one of its summit craters.

— Smithsonian Institution, Global Volcanism Program