How are volcanoes created?
In a volcano, eruption occurs when magma that has risen from underground reaches the surface, causing lava to flow and volcanic ash to accumulate, forming a volcano.Volcanoes are repeatedly formed and destroyed through eruptions.
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1.Occurrence of trench volcanoes
Trench volcanoes are volcanoes distributed along oceanic trenches where the oceanic plate is subducted beneath the continental plate, as in Japan. The subduction of the oceanic plate is greatly related to eruptions. |
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2.Generation of magma
Water entrained with the subducting oceanic plate melts a portion of the upper mantle, causing it to rise and generate magma. |
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3.magma reservoir
As magma rises and loses its buoyancy, it stops at a certain depth, and there is a place where magma gathers. This place is called magma chamber. |
 ©Source: Kurunavi “Volcanic Powerhouse Japan” |
4.eruption
When the magma in the magma chamber rises further. The surrounding rock can no longer withstand the pressure and breaks, and lava and volcanic ash are suddenly ejected from the surface. |
Main damage caused by volcanoes
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1.cinder block
Among the objects that fly in a trajectory unaffected by the wind during an eruption, those with a diameter of 20 to 30 cm or more are called large volcanic blocks. |
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2.pyroclastic flow
This is a phenomenon in which high-temperature volcanic ash and lava flow down slopes at high speed together with volcanic gas. |
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3.lava flow
A phenomenon in which molten rock flows over the earth's surface. Buildings, roads, farmland, forests, and villages are destroyed, leaving the land completely barren. |
©Source: Japan Meteorological Agency “Volcano”
Types of volcanoes
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Shield volcano ・The slope is gentle, so the area is wide. ・The viscosity of the magma is weak, and the lava is dark in color. ・The most famous volcano is Mauna Loa. |
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bell-shaped volcano ・The slope is steep and the viscosity is strong. ・The lava is whitish in color and erupts explosively. ・Representative volcanoes are Showa Shinzan and Unzen Fugendake. |
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stratovolcano ・It erupts over and over again from the same location, forming a cone shape. ・Mureike is between a shield volcano and a bell volcano, and the lava is gray in color. ・Representative volcanoes are Mt. Fuji and Mt. Asama. |
