Overview
This lecture explains the theory of plate tectonics, categorizes plate boundaries, and describes how large-scale Earth systems interact at those boundaries.
Plate Tectonics Basics
- The lithosphere is divided into rigid plates that move over the softer asthenosphere beneath.
- Plate movement is driven by convection currents in the mantle due to heat escaping from Earth's core.
- Plate tectonics explains continental drift, earthquakes, volcanoes, and mountain formation.
Types of Plate Boundaries
- There are three main types of plate boundaries: divergent, convergent, and transform.
- At divergent boundaries, plates move apart, typically forming mid-ocean ridges and new crust.
- At convergent boundaries, plates collide, causing subduction zones, earthquakes, and mountain ranges.
- At transform boundaries, plates slide horizontally past each other, often resulting in earthquakes.
Major Interactions and Features
- Divergent boundaries cause seafloor spreading and create rift valleys on land.
- Convergent boundaries result in ocean trenches, volcanic arcs, and uplifted mountains as one plate is forced under another.
- Transform boundaries are marked by fault lines, such as the San Andreas Fault, with significant earthquake activity.
Key Terms & Definitions
- Lithosphere — the rigid outer layer of Earth, comprising the crust and upper mantle.
- Asthenosphere — the semi-fluid layer beneath the lithosphere that allows plate movement.
- Divergent boundary — where two tectonic plates move away from each other.
- Convergent boundary — where two plates move toward each other, often resulting in subduction.
- Transform boundary — where plates slide past one another horizontally.
- Subduction zone — area where one plate is pushed beneath another into the mantle.
Action Items / Next Steps
- Review diagrams of plate boundary types and identify real-world examples.
- Prepare to discuss the effects of plate movement on natural disasters in the next class.