1. HOMEWORK
Read Section 9.2
Page 198 Q 1-3

2. How and Where Volcanoes Form
Section 9.1
Write what is in RED on the handout provided

3. Quick Review What is magma? Why does magma rise?
At what kind of plate tectonic boundary/ boundaries do we find volcanoes?
Why do volcanoes form here?

4. Definition of Volcano
Volcano: Both an opening in Earth’s crust through which molten rock, gases and ash erupt and to the landform that develops around this opening

5. Magma Formation
1. Decreasing pressure can lower the melting temperatures of materials in the asthenosphere (ex. Rift valley/mid-ocean ridge)
2. Increasing temperatures can cause materials in the astenosphere to melt. (ex. Hot spot)
3. Increasing water in the asthenosphere can lower melting temperatures (ex. Subduction boundaries)

6. Rise to the Top
Magma tends to rise to the surface because it is less dense than the solid material surrounding it
The traits of the magma and the rate at which is rises depends on the amount of silica

7. Please make this chart in your notes
Volcano Location
Reason
Volcano Formation
Special Notes
Examples

8. Subduction Boundary Divergent Boundary Hot Spot Row 1 Volcano Location
Reason
Volcano Formation
Special Notes
Examples
Subduction Boundary
Divergent Boundary
Hot Spot

9. Collision between Oceanic/Continental Or Oceanic/Oceanic
Row 2
Volcano Location
Reason
Volcano Formation
Special Notes
Examples
Subduction Boundary
Collision between Oceanic/Continental
Or Oceanic/Oceanic
Divergent Boundary
High temperature + low pressure = lots of magma
Hot Spot
Hot molten magma from deep within the Earth rises up through the crust and reaches the surface

10. On plate that does not sink
Row 3
Row 4
Row 5
Volcano Location
Reason
Volcano Formation
Special Notes
Examples
Subduction Boundary
Collision between Oceanic/Continental
Or Oceanic/Oceanic
On plate that does not sink
Divergent Boundary
High temperature + low pressure = lots of magma
Where the plates separate
Hot Spot
Hot molten magma from deep within the Earth rises up through the crust and reaches the surface
In the middle of plates away from plate boundaries

11. oceanic/oceanic, forms “VOLCANIC ARC”
Row 4
Volcano Location
Reason
Volcano Formation
Special Notes
Examples
Subduction Boundary
Collision between Oceanic/Continental
Or Oceanic/Oceanic
On plate that does not sink
oceanic/oceanic, forms “VOLCANIC ARC”
Divergent Boundary
High temperature + low pressure = lots of magma
Where the plates separate
Most of these volcanoes are underwater
Hot Spot
Hot molten magma from deep within the Earth rises up through the crust and reaches the surface
In the middle of plates away from plate boundaries
Hot spots do not move, but the crust does

12. O/C: Cascades in California O/O: Aleutians in Alaska
Row 5
Volcano Location
Reason
Volcano Formation
Special Notes
Examples
Subduction Boundary
Collision between Oceanic/Continental
Or Oceanic/Oceanic
On plate that does not sink
oceanic/oceanic, forms “VOLCANIC ARC”
O/C: Cascades in California
O/O: Aleutians in Alaska
Divergent Boundary
High temperature + low pressure = lots of magma
Where the plates separate
Most of these volcanoes are underwater
Mid-ocean ridge, Iceland
Hot Spot
Hot molten magma from deep within the Earth rises up through the crust and reaches the surface
In the middle of plates away from plate boundaries
Hot spots do not move, but the crust does
Hawaiian Islands, Canary Islands, Yellowstone