1. Chapter 7 Section 1
Key terms: Volcano, magma, lava, ring of fire, island arc, hot spot
Key concepts: Where are most of Earth’s volcanoes found? How do hot spot volcanoes form?

2. Volcanoes are not your buddies
A volcano is a weak spot in the crust where magma comes through
Magma is a molten mixture of rock, gas, and water
When magma reaches the surface, it is called lava. When lava cools, it forms solid rock (igneous)

3. Volcanoes and plate boundaries are buddies
One major volcanic belt is the Ring of Fire around the Pacific Ocean
Volanic belts form around the boundaries of Earth’s plates
At plate boundaries, huge pieces of the crust diverge or converge. The crust fractures and magma is allowed to reach the surface.

4. Diverging boundaries (moving away)
Volcanoes form along mid ocean ridges (long, underwater mountain ranges that sometimes have a rift valley down the center. Lava pours out of cracks in the ocean floor, eventually making new mountains.

5. Converging boundaries (coming together)
Where oceanic plates return to the mantle
Volcanoes form where plates collide with a continental plate.
Older, denser plates sink. The rock above the plate melts and forms magma. Because magma is less dense, it rises to the surface. Eventually, the magma breaks through the ocean floor, creating volcanoes.

6. Converging continued
The resulting volcanoes create a string of islands called an island arc. (Japan, New Zealand, Caribbean Islands)
Volcanoes also occur where an oceanic plate is subducted beneath a continental plate.

7. Hot Spot Volcanoes
A hot spot is an area where material from deep within the mantle rises and then melts, forming magma. A volcano forms above a hot spot when magma erupts through the crust and reaches the surface.
It can gradually form a series of volcanic mountains.