The 26 x 20 km wide Kussharo Caldera, also known as Kutcharo Caldera, was formed during series of major explosive eruptions between 340'000 and 30'000 years ago. The caldera forms together with the Akan Caldera and Mashu Caldera the Akan Nationalpark.
The Lake Kussharo covers most of the western half of the caldera. A less than 10'000 years old lava-dome is forming an island in the lake, known as Nakajima. The Mount Iozan ("Sulfur Mountain") is an active volcano and part of the Kussharo Caldera.
Japan 1950, Kussharo Caldera Lake.
The stamp was issued in sheets of 20 stamps and in the miniaturesheet "Akan Nationalpark".
The Mt. Iozan is a 508 m high active volcano with hissing vents, clouds of steam and bright yellow sulphur deposits. In the background there is the Kussharo Caldera Lake.