1. Volcanoes & Plate Tectonics

2. 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

4. 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

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

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

7. 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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9. 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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