The caldera of the Uzon volcano is another major natural attraction in Kamchatka; it is a huge depression that is 9 by 12 km with an area of 150 square kilometres. It developed on the site of a destroyed volcano. From a bird's-eye view, Uzon looks like a huge bowl made up of two cupped hands (caldera means "cauldron" in Spanish).
The bottom of the caldera is a relatively flat lowland at 650 m above sea level. The sides are made of black basalt and rise another 500 m to 960 m. The lowest areas of the caldera are wetlands with areas of tundra in the western and south-western parts.
In the northern part of the caldera, there are five separate geothermal fields, including the Eastern, the Ozyornoye (located near Fumarolnoye Lake), the Western, the Northern, and the Southern geothermal fields. There are some smaller geothermal fields between the Eastern and Northern fields, including the Tsepochka, the Oranzhevaya, the Vosmyorka, and the Kraynyaya. In the caldera, there are about 100 springs and over 500 individual hydrothermal manifestations of virtually all the types of waters found in Kamchatka. The total heat output produced by natural heat carriers is 70 thousand kcal/sec.
Among the most remarkable lakes in the caldera are:
- Central Lake (the largest but shallowest and coldest lake);
- Fumarolnoye Lake (warm and non-freezing)4
- Bannoye Lake (with a constant temperature of 40°C and a false bottom of molten native sulfur);
- Utinoye Lake (with a unique sulfur beach).
The caldera of the Uzon volcano is unique in that it has the characteristics of a young volcano, mineral and ore formation, the development of thermal lakes, the emergence of the world's youngest oil, and microbiological processes in thermal springs. The caldera also has diverse fauna: the ground heat attracts animals, and sandpipers, whooper swans, and various duck species nest at the geothermal fields.
About 370,000 to 750,000 years ago, there was a large shield volcano at the caldera site that was pouring out highly mobile basaltic lava. The modern Uzon caldera was formed about 40,000 years ago as a result of powerful movements of the Earth's crust.