1. Vocabulary convection The movement of materials based on density. Warm materials are less dense, so they rise and cool, becoming more dense and then sink.

2. Vocabulary convection The movement of materials based on density. Warm materials are less dense, so they rise and cool, becoming more dense and then sink.

3. Vocabulary sea floor spreading The process by which the oceanic lithosphere is created as older materials are pulled apart at a divergent boundary.

4. Vocabulary sea floor spreading The process by which the oceanic lithosphere is created as older materials are pulled apart at a divergent boundary.

5. Vocabulary sea floor spreading The process by which the oceanic lithosphere is created as older materials are pulled apart at a divergent boundary.

6. Vocabulary sea floor spreading The process by which the oceanic lithosphere is created as older materials are pulled apart at a divergent boundary.

7. Vocabulary sea floor spreading The process by which the oceanic lithosphere is created as older materials are pulled apart at a divergent boundary.

8. Vocabulary subduction The process by which an oceanic plate sinks down into the asthenosphere at a convergent boundary, usually between continental and oceanic plates.

9. Vocabulary subduction The process by which an oceanic plate sinks down into the asthenosphere at a convergent boundary, usually between continental and oceanic plates.