The massive Iyang-Argapura volcanic complex dominates the landscape between Raung and Lamongan volcanoes in eastern Java. Valleys up to 1000 m deep dissect the strongly eroded basal Iyang volcano. Several Holocene volcanic cones have been constructed at the center of a N-S-trending central rift. No major eruptions have occurred within at least the last 500 years, although there was an unverified report of an eruption in 1597 AD. Fumaroles occur in some of the many explosion pits found in the summit crater complex.