Volcanoes Plate Tectonics What is a Volcano n

Volcanoes & Plate Tectonics

What is a Volcano? n. 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… n Volcanic belts form along the boundaries of Earth’s plates n Remember…at plate boundaries plates diverge or converge – Causes crust to fracture allowing magma to reach surface

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

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

Converging Boundaries n 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 n Creates string of islands called island arc (Japan, Philippines, Caribbean Islands)

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Hot Spot Volcanoes n 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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