Overview
This lesson covers the three main types of plate boundaries (divergent, convergent, and transform), the different kinds of convergent boundaries, and examples of locations where these occur.
Plate Boundaries Introduction
- Plate boundaries are the edges where two lithospheric plates meet.
- Plate movement is driven by convection currents in the Earth's interior.
- Plate boundaries cause earthquakes, volcanism, and mountain formation.
Types of Plate Boundaries
Divergent Boundaries
- Divergent boundaries form when two tectonic plates move apart.
- New crust is created as magma rises and solidifies at these boundaries.
- Also called "constructive boundaries."
- Mid-ocean ridges and continental rift valleys form at divergent boundaries.
- Example: The Mid-Atlantic Ridge (Eurasian and North American plates).
Convergent Boundaries
- Convergent boundaries occur when two plates move toward each other.
- There are three types: oceanic-continental, oceanic-oceanic, and continental-continental.
- Oceanic-Continental: Oceanic plate subducts under continental plate, causes volcanism.
- Oceanic-Oceanic: One oceanic plate subducts under another, forming volcanic island arcs and trenches.
- Continental-Continental: Plates collide, crumple, and form mountain ranges like the Himalayas.
- Subduction is the process where one plate moves beneath another.
Transform Boundaries
- Transform (strike-slip) boundaries occur when two plates slide past each other horizontally.
- Rocks along the boundary break and slip, forming faults.
- Example: The San Andreas Fault (Pacific and North American plates).
- Can create undersea canyons and linear fault valleys.
Key Terms & Definitions
- Plate boundary — The line where two lithospheric plates meet and interact.
- Divergent Boundary — Plates move away from each other; new crust forms.
- Convergent Boundary — Plates move toward each other, causing subduction, volcanism, or mountain formation.
- Transform Fault Boundary — Plates slide past each other horizontally.
- Subduction — The process where one tectonic plate moves beneath another at a convergent boundary.
- Mid-ocean ridge — An underwater mountain range formed by divergent boundaries.
- Oceanic trench — A deep underwater trench formed at subduction zones.
- Compression — The process of plates pushing against each other, thickening the crust.
Action Items / Next Steps
- Review examples of each boundary type (Mid-Atlantic Ridge, Himalayas, San Andreas Fault).
- Practice identifying boundary types based on plate movement and features formed.
- Complete any assigned activity on classifying plate boundary diagrams.