Niikappu mud volcano, Mud volcano in Niikappu, Hokkaido, Japan

Niikappu mud volcano is a group of hills along National Route 235, about 2 km north-northwest of Niikappu town centre, where mud and water seep out at the surface. Eight mounds were once recorded; today only four remain, numbered First and Sixth to Eighth, and the Eighth is the largest and most active.

The mud volcanoes formed after the last glacial period, and their present shape was largely complete before the 1663 eruption of Mount Usu. Mud and ground deformation were recorded mainly at the eighth hill during major earthquakes, including the 1952 and 2003 Tokachi-oki earthquakes. The site is a Hokkaido Prefectural Natural Monument.

The name Niikappu mud volcano covers a row of hills along National Route 235, about 2 km north-northwest of Niikappu town centre. Eight were once recorded; today only the first and sixth to eighth remain, and the eighth, the largest and most active, is the one usually seen from the road.

The mud volcanoes stand on private pasture land, so visitors can only view them from a distance, mainly along National Route 235. Entry is allowed only for academic research with the landowner's permission. Four of the original eight cones remain, and the eighth is the largest and most active.

The mud volcanoes are not volcanic landforms: they sit where an anticline is cut by faults, and gas, mud and soil erupt after large earthquakes. Eruptions were recorded at the eighth mound during the 1952, 1968, 1981, 1994, 2003 and 2008 earthquakes.