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USGS CMG InfoBank: Island Arc System

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Comment: 07:45 - 08:41 (00:56)
Source: Annenberg/CPB Resources - Earth Revealed - 6. Plate Dynamics
Keywords: "plate tectonics", plate, subduction, trench, earthquake, mantle, crust, basalt, "oceanic crust", pressure, magma, andesite, eruption, "volcanic chain", island, "island arc"

Our transcription: As the plate sinks, earthquakes occur within it.
These quakes range from shallow events at the trench itself to very deep cataclysms near the heated end of the descending slab as much as 700 kilometers beneath the surface.
These earthquakes can be used to trace the descent of the subducting plate into the mantle.
By diving into the mantle, the subducting plate creates friction and heat, and the basaltic oceanic crust partially melts under the intense pressure.
The molten rock rises, ultimately reacting with overlying rock to form andesitic magma, which erupts in curving or arc shaped chains of volcanoes.
The volcanic chain parallels the ocean trench and at sea forms a string of volcanic islands known as an "Island Arc System."

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