Overview
This lesson explains the different types of plate boundaries, compares types of convergent boundaries, and identifies where these boundaries are found on Earth.
Plate Boundaries Overview
- Plate boundaries are the edges where different lithospheric plates meet and interact.
- Plate movement is caused by convection currents within the Earth's interior.
- The three main plate boundary types are divergent, convergent, and transform.
Divergent Boundaries
- Divergent boundary: plates move apart from each other, creating tension.
- New crust forms as magma rises and solidifies at the surface.
- Also called constructive boundary.
- Examples: mid-ocean ridges (e.g., Mid-Atlantic Ridge), continental rift valleys.
- Divergent boundaries often cause earthquakes and form new oceanic crust.
Convergent Boundaries
- Convergent boundary: plates move toward each other.
- Three types:
- Oceanic-continental: oceanic plate subducts beneath continental plate (process called subduction); can form volcanic mountains.
- Oceanic-oceanic: one oceanic plate subducts beneath another, forming island volcanic chains and trenches.
- Continental-continental: plates collide, causing compression and mountain formation (e.g., Himalayas).
- Subduction zones are marked by deep oceanic trenches and volcanic activity.
Transform Fault Boundaries
- Transform boundary: plates slide past each other horizontally.
- Also called strike-slip or transform fault.
- Rocks along the boundary break and slip, creating linear valleys or undersea canyons.
- Example: San Andreas Fault in California.
How Boundaries Relate to Geological Features
- Plate interactions cause earthquakes, volcanic activity, and mountain building.
- Each boundary type produces distinct geological features based on plate motion.
Key Terms & Definitions
- Plate Boundary — the line where two tectonic plates meet and interact.
- Divergent Boundary — boundary where plates move apart and new crust forms.
- Convergent Boundary — boundary where plates move toward each other and may subduct or collide.
- Subduction — process where one plate bends downward into the mantle beneath another plate.
- Transform Fault — boundary where plates slide past each other horizontally.
- Compression — squeezing and folding of Earth's crust during plate collision.
Action Items / Next Steps
- Review the different types of plate boundaries and their key features.
- Practice identifying real-world examples of each boundary type.
- Prepare for the next lesson by studying related geological features.