Knowra Stratovolcano Stratovolcano A steep-sided volcano built from alternating layers of lava, ash, and other volcanic debris. Its viscous, gas-rich magma can produce explosive eruptions.
Subduction zone : A region where one tectonic plate descends beneath another into the mantle. Many stratovolcanoes form above descending oceanic plates that release water into the mantle.
Lava : Molten rock that has erupted onto Earth’s surface. Repeated lava flows contribute solid layers to a stratovolcano’s flanks.
Mount Fuji : A 3,776-meter stratovolcano on Japan’s Honshu island and a prominent national symbol. Its symmetrical cone is a widely recognized example of stratovolcano form.
Shield volcano : A broad, gently sloping volcano built mainly by repeated flows of low-viscosity lava. Its fluid lava builds wide slopes rather than the steep layered cone typical of stratovolcanoes.
Andesite : A fine-grained volcanic rock with intermediate silica content, commonly composed of plagioclase and other minerals. Andesitic magma is common in stratovolcanoes and can be viscous enough to trap gases.
Volcanic ash : Fragments of volcanic rock, minerals, or glass smaller than two millimeters, blasted into the air during eruptions. Ash falls between lava deposits, helping build the volcano’s alternating layers.
Mount St. Helens : An active stratovolcano in Washington State, United States, that erupted catastrophically in 1980. Its 1980 eruption demonstrated how flank collapse and explosive activity can reshape a stratovolcano.
Cinder cone : A small, steep volcano built mainly from loose fragments ejected around a vent. It is typically simpler and smaller than a stratovolcano, with less extensive lava-and-debris layering.
Magma chamber : A subsurface reservoir or network of molten rock and crystals beneath a volcano. Magma accumulates and evolves below many stratovolcanoes before rising toward the surface.
Tephra : Any fragment of volcanic material ejected into the air during an eruption, regardless of size. Ash, lapilli, and blocks are all tephra that can accumulate around a stratovolcano.
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