Volcanoes erupt when molten rock called magma rises to the surface. Magma is formed when the earth's mantle melts. Melting may happen where tectonic plates are pulling apart or where one plate is pushed down under another. If magma is thick, gas bubbles cannot easily escape and pressure builds up as the magma rises.
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Answer:
Volcanoes erupt when molten rock called magma rises to the surface. Magma is formed when the earth's mantle melts. Melting may happen where tectonic plates are pulling apart or where one plate is pushed down under another. If magma is thick, gas bubbles cannot easily escape and pressure builds up as the magma rises.
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Answer:
volcanoes form when one tectonic plate moves under another