1. Plate Tectonic Booklet Convection Currents

2. Example: Mid-Atlantic Ridge Effects: 1. Creates a submarine mountain range 2. Volcanic activity in the form of fissure eruptions 3. Shallow earthquake activity 4. Creates new sea floor and widens ocean basins Example: East African Rift Valley Effects: 1. Sometimes occupied by fresh or salt water 2. Many normal faults in the rift valley 3. Shallow earthquakes along the faults 4. Sometimes there is volcanic activity in the rift valley Magma from the mantle

3. Mid-Atlantic Ridge East African Rift Valley

4. Example: Andes Mountains in South America Effects: 1. A zone of earthquake activity along the continent margin 2. Sometimes ocean trenches form offshore 3. A line of volcanic eruptions a few hundred miles inland 4. Destruction of oceanic crust Example: Aleutian islands Effects: 1. A zone of progressively deeper earthquakes 2. An oceanic trench 3. A chain of volcanic islands 4. Destruction of oceanic crust

5. Mid-Atlantic Ridge East African Rift Valley Andes Mountains Aleutian islands

6. Example: Himalaya Mountain Range Effects: 1. Intense folding and faulting 2. A broad folded mountain range 3. Shallow earthquake activity 4. Shortening and thickening of the continental plates Example: San Andreas Fault Effects: 1. Location of recurring earthquake activity and faulting 2. The earthquakes are usually shallow 3. Volcanic activity is normally NOT present

7. Mid-Atlantic Ridge East African Rift Valley Andes Mountains Himalaya Mountains Aleutian islands San Andreas Fault

8. Theory of Continental Drift-- the theory that the earth's continents move gradually over the surface of the Earth. Theory of Plate Tectonics-- the theory that the Earth’s lithosphere is broken into plates that float on the asthenosphere. Convection current-- cooler, denser rock near the astenosphere sinks while hotter, less dense rock in the lower mantle rises driving the movement of the tectonic plates. Tension-- a force that pulls two plates apart from each other. Divergent Boundary-- plate boundary where two plates are moving away from each other because of tension. Compression-- a force that pushes two plates together. Convergent Boundary-- plate boundary where two plates are pushed together because of compression. Subduction--A type of plate movement that happens when one plate sinks beneath another plate. Shear force– a force that fractures rock along a plane because of movement in opposite directions. Transform Boundary– plate boundary where two plates are moving parallel to each other in opposite directions because of shear force.