Department of Biological Sciences and Geology

Close-Up--Plate Tectonics Theory


Stratovolcanoes are made of layers of pyroclastics and lava from successive eruptions. As long as a stratocone continues to have a conical shape it should be considered a potential killer.

The magma that is extruded to make the stratovolcano is intermediate in composition, and is generated by partial melting of subducted ocean plate material and the sediments that mantle the subducting slab. Water vapor is the major gas that causes explosive volcanism and the more viscous intermediate magma holds back the high pressure gases until there is catastrophic failure leading to an explosion.

Composite or Stratovolcano

Stratovolcanoes occur all around the Pacific rim and up to around 150 km inland from the coast. These volcanoes give the rim its nickname "the Ring of Fire."

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