Volcanoes & Plate Tectonics

What is a Volcano? A weak spot in the crust where molten material comes to the surface Magma – a molten mixture of rock-forming substances, gases, and water from the mantle When reaches the surface called lava Forms solid rock after cools Builds up Earth’s surface

Volcanoes & Plate Boundaries cont… Volcanic belts form along the boundaries of Earth’s plates Remember…at plate boundaries plates diverge or converge Causes crust to fracture allowing magma to reach surface

Example of Volcano at plate boundaries Mount Etna – Eurasian & African plates

Divergent Boundaries Form along mid-ocean ridges Ocean floor slowly builds up forming new mountains Examples…Great Rift Valley in East Africa

Converging Boundaries Form where 2 oceanic plates collide Older plate sinks beneath trench into mantle Some rock above subducting plate melts & forms magma Magma is less dense than rock, so rises toward surface Breaks through ocean floor creating volcano Creates string of islands called island arc (Japan, Philippines, Caribbean Islands)

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Hot Spot Volcanoes Hot spot – area where material from deep within mantle rises then melts forming magma Volcano forms when magma erupts through crust and reaches surface Can be found in middle of plates (away from boundaries) or at boundaries Can form series of volcanic mountains (Hawaiian Islands) Can form under continents (Yellowstone National Park in Wyoming)

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