Akan volcano (阿寒岳, Akan-dake) is one of Hokkaido's most active volcanoes. Akan consists of a large 24 x 13 km diameter caldera and a group of younger partly Holocene andesite cones. The highest point of the complex is the Mount Meakan (1499 m) stratovolcano. The frequent historic eruptions occurred all from the Me-Akan group, east of Lake Akan. Me-Akan volcano (雌阿寒岳 Meakan-dake) consists of 9 overlapping cones. Its summit has 3 craters. Me-Akan has had at least 17 small phreatic eruptions since the beginning of the 19th century and from geologic studies it is known that there were at least 4 major magmatic eruptions with pyroclastic flows have occurred in prehistoric time during the past 10,000 years. Lake Akan is part of the Akan National Park. It is known for a rare green algae (marimo) which can grow to about the size of a soccer ball. The only town around the lake is the resort of Akankohan known for its hot springs and the "bokke", bubbling mud pools found at the lakeshore.

The Akan caldera is located immediately SW of Kutcharo caldera and has an elonogated, irregular shape due to several caldera-forming explosive eruptions between the early and mid Pleistocene.

Growth of 3 post-caldera stratovolcanoes, 3 at the SW end of the caldera and the other at the NE side, has reduced the size of the caldera lake. The conical O-Akan volcano was frequently active during the Holocene. The 1-km-wide Nakamachineshiri crater of Me-Akan volcano was formed during a major pumice-and-scoria eruption about 13,500 years ago.