Overview
This lecture explains the three main types of plate boundaries—convergent, divergent, and transform—and describes the processes and landforms associated with each.
Types of Plate Boundaries
- Plate boundaries are the edges where two tectonic plates meet.
- There are three major types: convergent, divergent, and transform boundaries.
Convergent Plate Boundaries
- Convergent boundaries occur where two plates move toward each other.
- Oceanic-continental convergence forms trenches and volcanic arcs (e.g., Andes Mountains).
- Oceanic-oceanic convergence forms deep sea trenches and island arcs (e.g., Marianas Trench).
- Continental-continental convergence forms high mountain ranges (e.g., Himalayas).
Divergent Plate Boundaries
- Divergent boundaries occur where two plates move away from each other.
- Most often found at mid-ocean ridges, creating new oceanic crust.
- Can also occur on land, forming rift valleys (e.g., East African Rift Valley).
Transform Plate Boundaries
- Transform boundaries occur where two plates slide past each other horizontally.
- Feature strong earthquakes due to stress build-up and release (e.g., San Andreas Fault).
- No major landforms are created, and crust is neither destroyed nor created.
Landforms and Geologic Events
- Convergent boundaries cause earthquakes, volcanic eruptions, mountain formation, and deep-sea trenches.
- Divergent boundaries cause seafloor spreading, formation of new crust, and rift valleys.
- Transform boundaries cause frequent, strong earthquakes.
Key Terms & Definitions
- Plate Boundary — The region where two tectonic plates meet.
- Convergent Boundary — A boundary where plates move toward each other and collide.
- Divergent Boundary — A boundary where plates move apart from each other.
- Transform Boundary — A boundary where plates slide past each other.
- Trench — A deep area in the ocean where one plate is subducted under another.
- Rift Valley — A lowland region formed where Earth's tectonic plates move apart.
- Subduction — The process of one plate sinking beneath another.
Action Items / Next Steps
- Review diagrams of different plate boundaries and associated landforms.
- Prepare examples of each type of plate boundary for class discussion.