User:The Cosmonaut/Sandbox/Uzon

The Uzon Caldera is a caldera located within the Kronotsky Nature Reserve in the Russian Kamchatka region.

Geology
A large shield volcano was active in the western part of the modern depression during the Pleistocene, 370—750 kya, erupting fluid basaltic lavas that covered large areas of the surrounding flat terrain. Its centre has been reconstructed at the northern part of the Uzon-Geyser Depression. Deposits of lava and tuff are well-exposed at the western flank of the caldera. By mid-Pleistocene, 225—370 kya, a stratovolcano began growing on the western slope, eventually reaching the heghy of up to 3 km. It was composed of the same two-pyroxene olivine-containing basalts with some pyroclastics as the shield volcano, but contained more silica. The system became highly active 175—225 kya. Explosive eruption produced a giant crater in the eastern part of the system, producing large flows of glassy felsic lava that formed the ignimbrites around the structure.