Overview
This lecture covers the three types of convergent plate boundaries, their geological formations, and how Earth's crust is recycled through these processes.
Introduction to Convergent Plate Boundaries
- Plate boundaries are edges where two tectonic plates meet.
- Convergent boundaries occur when plates collide due to compressional stress.
- Collision leads to elevation or subduction, forming various landforms.
Types of Convergent Boundaries
Continental-Continental Convergence
- Two continental crusts collide and both are uplifted, forming mountain features.
- Common formations: mountains, mountain ranges, hills.
- No subduction occurs because both crusts are relatively light.
- Notable examples: Mount Everest, Himalayan Mountain Range, Sierra Madre in the Philippines, Chocolate Hills.
Oceanic-Oceanic Convergence
- Two oceanic crusts collide; the older, denser crust subducts under the younger crust.
- Produces volcanoes, islands, and deep ocean trenches.
- Notable examples: Augustine Volcano (Alaska), 100 Islands (Philippines), Mariana Trench (deepest trench).
Oceanic-Continental Convergence
- The denser oceanic crust subducts beneath the lighter continental crust.
- Creates volcanoes and trenches but not islands.
- Subduction results in magma formation and volcanic eruptions.
The Subduction Cycle and Earth’s Matter Recycling
- Subducted crust sinks to the mantle and melts to form magma.
- Magma rises and is expelled by volcanoes as lava.
- Lava cools into rocks, becoming part of the crust again.
- This cycle recycles Earth's landforms without human involvement.
Recap & Application (Q&A)
- Oceanic-oceanic convergence forms volcanoes, islands, and trenches.
- Oceanic-continental convergence forms volcanoes and trenches.
- Continental-continental convergence forms mountains, ranges, and hills; no subduction occurs.
- Compression is the driving stress for all convergent boundaries.
Key Terms & Definitions
- Convergent Boundary — where two tectonic plates move towards each other and collide.
- Compression — driving stress that pushes plates together.
- Subduction — process where one plate sinks beneath another.
- Magma — molten rock beneath Earth's surface.
- Lava — magma that reaches Earth's surface.
- Trench — deep area where subduction occurs.
- Mountain Range — a series of connected mountains.
Action Items / Next Steps
- No homework assigned; review the video for reinforcement.
- Enjoy your long weekend; class resumes on Tuesday.