1. 9.3 Actions at Plate Boundaries
Divergent Boundaries-tectonic plates
move apart
9.3 Actions at Plate Boundaries
 Oceanic Ridges and Seafloor Spreading
• Oceanic ridges are continuous elevated zones on the floor of all major ocean basins.
• Seafloor spreading produces new oceanic lithosphere.

2. 9.3 Actions at Plate Boundaries
Oceanic Ridges example- Mid-Atlantic Ridge
9.3 Actions at Plate Boundaries

3. Spreading Center Divergent tectoniv plate boundary Seafloor spreading
Mid-ocean ridge

4. 9.3 Actions at Plate Boundaries
Convergent Boundaries-
Occur when two plates move together
Three kinds of convergent plate boundaries:
Oceanic-Continental
Continental –Continental
Oceanic-Oceanic

5. 1. Oceanic-Continental Convergent Boundary
• Continental volcanic arcs form in part by volcanic activity caused by the subduction of oceanic crust beneath a continent. Examples include the Andes Moujntains
along the west coast of South America.

6. 9.3 Actions at Plate Boundaries
Convergent Boundaries
9.3 Actions at Plate Boundaries
2. Oceanic-Oceanic
• Two oceanic slabs converge and one descends beneath the other.
• Volcanic island arcs form as volcanoes emerge from the sea.
• Examples include the Aleutian, Mariana, and Tonga islands.

7. 2. Oceanic-Oceanic Convergent Boundary

8. 9.3 Actions at Plate Boundaries
Convergent Boundaries
9.3 Actions at Plate Boundaries
3. Continental-Continental
• When 2 continents collide
• This kind of boundary can produce new mountain ranges, such as the Himalayas.

9. Collision of India and Asia

10. Testing Plate Tectonics
Evidence for Plate Tectonics
Testing Plate Tectonics
 Hot Spots
A hot spot is a concentration of heat in the mantle capable of producing magma, which rises to Earth’s surface;
The Pacific tectonic plate moves over a hot spot, producing the Hawaiian Islands.
Hot spot evidence supports that the plates move over the Earth’s surface.

11. Hot Spot

12. Convergent Plate Boundaries Summary
1. Oceanic-Oceanic
Ocean crust moves under ocean crust
Produces volcanic islands
Example Aleutian Islands
2. Continental-Continental
Continents move into each other
Prodices mountains
Example Himalayan Mountains of Nepal
3. Oceanic –Continental
Ocean crust moves under a continent
Produces Volcanic arcs
Example Andes Mountains