Overview
This lecture covers the structure of tectonic plates, their movement, and the types of boundaries formed, explaining how these processes shape Earth's surface and cause geological events.
Structure of the Earth
- The Earth has three main layers: the core, mantle, and crust.
- The crust and upper mantle form the lithosphere, which is broken into tectonic plates.
- Below the lithosphere lies the partially molten asthenosphere, which allows plates to move.
Tectonic Plates
- Tectonic plates are large, rigid sections of Earth's lithosphere.
- Plates can include both continental and oceanic crust.
- There are seven major plates and several minor ones worldwide.
Plate Movement
- Plates move due to convection currents in the mantle.
- Plate movements are slow, typically a few centimeters per year.
- Plate tectonics is responsible for the changing positions of continents over time.
Types of Plate Boundaries
- Divergent boundaries: plates move apart, allowing new crust to form (e.g., mid-ocean ridges).
- Convergent boundaries: plates move towards each other, causing subduction or mountain building.
- Transform boundaries: plates slide horizontally past each other, often creating earthquakes.
Geological Features and Hazards
- Earthquakes commonly occur at plate boundaries due to stresses and movement.
- Volcanoes often form near convergent and divergent boundaries.
- Mountain ranges are produced by the collision of continental plates.
Key Terms & Definitions
- Tectonic Plate — A rigid segment of Earth's lithosphere that moves over the asthenosphere.
- Lithosphere — The rigid outer layer of Earth, including the crust and uppermost mantle.
- Asthenosphere — The partially molten, flexible region of the upper mantle beneath the lithosphere.
- Convection Current — The movement of material in the mantle driving plate motion.
- Divergent Boundary — A location where two tectonic plates move apart.
- Convergent Boundary — A location where two plates move toward each other.
- Transform Boundary — A location where two plates slide horizontally past each other.
- Subduction — The process where one plate is forced below another at a convergent boundary.
Action Items / Next Steps
- Review the types of plate boundaries and memorize examples for each.
- Study images of tectonic plate boundaries and related features.
- Prepare for a quiz on key terms and definitions.