Plate Boundaries - Quick Reference

Definition: plates move apart; new crust forms at the gap.
Interactions:
- Continental-Continental Divergence ( $C-C$ )
- Rift valleys form; can evolve into new ocean basins.
- Example: Great Rift Valley, Africa.
- Oceanic-Oceanic Divergence ( $O-O$ )
- Seafloor spreading; formation of new oceanic crust; mid-ocean ridges.
- Example: Mid-Atlantic Ridge.
- Oceanic-Continental Divergence ( $O-C$ )
- Rift valleys form; potential new ocean basin (rifting).
- Example: South Atlantic Rift.
Key landforms/concepts:
- Rift valley, mid-ocean ridge, seafloor spreading, new crust creation.

Definition: plates move toward each other; different outcomes based on plate types.
Interactions:
- Continental-Continental Convergence ( $C-C$ )
- Neither plate subducts; intense compression; mountain building.
- Example: Himalayas (India-Asia collision).
- Continental-Oceanic Convergence ( $C-O$ )
- Oceanic plate subducts beneath continental plate; trenches form; volcanic arcs on continental crust.
- Example: Andes, Cascades.
- Oceanic-Oceanic Convergence ( $O-O$ )
- Older oceanic plate subducts under younger; trenches form; volcanic island arcs develop.
- Example: Mariana Trench region, other volcanic island arcs.
Key landforms/concepts:
- Trench, subduction zone, volcanic arc, mountain ranges, earthquakes.

Definition: plates slide past one another horizontally (shear).
Features:
- Shallow earthquakes, fault lines, lateral rock displacement.
- Volcanoes are rare at these boundaries.
Example: San Andreas Fault (California).