Oshima as an island stratovolcano with a large caldera on its summit. Stratovolcanoes are conical volcanoes built up by many layers of hardened lava and volcanic ash, with steep profiles and periodic eruptions.Continue Reading
The main stratovolcano cone of the island has a base composed of basalt lava and pyroclastic rocks. When an erupting volcano empties a shallow magma chamber, the volcanic formation can collapse into the voided reservoir and produce a cauldron-like depression.
Based on geological evidence, it is estimated that Oshima has erupted over 100 times since 8450 B.C. As of 2014, the last eruption was in 1990 at the summit of Mihara-yama.Learn more about Volcanoes
A caldera forms as a volcano's magma chamber empties, resulting in a loss of support for the earth above it. These bowl-shaped depressions can range in size from a few hundred meters to several kilometers wide. They are generally caused by large volcanic eruptions.Full Answer >
Mount Tambora is a stratovolcano, also known as a composite volcano. In addition to a stratovolcano's conical form, other common characteristics include the volcano's steep profile, thick lava that hardens quickly and a composition that includes layers of lava, ash and fragments pushed from the volcano during an eruption.Full Answer >
A composite cone volcano, or a stratovolcano, is built by multiple eruptions from surrounding volcanoes. They are formed over hundreds of thousands of years and have their entire structure build by magma flowing from geographically close volcanoes.Full Answer >
Mount Pinatubo is an active stratovolcano, or a cone-shaped volcano, that is made from many layers of hardened ash, lava and other volcanic rock. Stratovolcanoes are also called composite volcanoes.Full Answer >