The Nipesotsu-Maruyama volcano group, located west of Nukabira lake about 20 km east of Tokachi-dake 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 2013-m-high Nipesotsu-yama 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 Maru-yama, which means "Round Mountain."  A minor phreatic eruption took place at Maru-yama lava dome in 1898, and fumaroles are present on one of its summit craters.