A caldera is a vast cirque–shaped basin of volcanic origin, often with steep walls and a more or less flat bottom. Such a lowering of the relief is formed on the volcano after the collapse of the walls of the crater or as a result of its catastrophic eruption.
Golovnina Volcano is an active volcano on the island of Kunashir, the southernmost volcano of the Kuril Islands. The last eruption was in 1998. The caldera with a diameter of up to 4.7 km is surrounded by a ridge up to 541 m high . At the bottom of the caldera there are 4 small volcanic domes and 2 explosive craters, in one of which there are two lakes, they emit jets of gases, thick steam and hot water to the surface. One of them is named Hot, and the second, which is located directly in one of the craters, is Boiling Lake Kipyashchiy. There are a large number of sulfuric and sulfide compounds in lakes, and sulfide-sulfur foam floats on KipyashchiyBoiling water at all. You can get here only through the Kurilsky Nature Reserve.