Overview
This lesson introduces tectonic plates, Earth's compositional layers, and helps students sketch the locations of major plate boundaries using earthquake data.
Earth's Structure and Tectonic Plates
- Earth is divided into three main layers: crust, mantle, and core.
- The crust is a thin outer layer above the thick mantle.
- The mantle surrounds a two-part core: a solid inner core and a molten outer core.
- A tectonic plate includes the crust and the rigid uppermost mantle, forming the lithosphere.
- The lithosphere is several hundred kilometers thick and floats atop the asthenosphere.
- The asthenosphere is partially molten, allowing the overlying plates to move slowly.
Plate Movement and Boundaries
- The lithosphere is divided into separate tectonic plates, like pieces of orange skin.
- Plates move relative to each other, causing earthquakes, volcanoes, and mountain formation at their boundaries.
- Plate boundaries are identified by the distribution of tectonic activity such as earthquakes.
Mapping Plate Boundaries
- Earthquake location data helps reveal plate boundaries.
- Major boundaries include the Atlantic Ocean ridge and plate separations in the Pacific and Indian Oceans.
- By tracing earthquake zones, students can outline major tectonic plates.
- Most plates are named after continents or oceans.
Major and Minor Plates
- The eight major plates: Pacific, North American, South American, African, Eurasian, Antarctic, Indian-Australian, and Nazca.
- Smaller plates include Cocos, Caribbean, Scotia, Philippine, and Arabian.
Key Terms & Definitions
- Tectonic Plate — A rigid slab of the lithosphere (crust and uppermost mantle) that moves over the asthenosphere.
- Lithosphere — The solid, outer layer of Earth, comprising the crust and upper mantle.
- Asthenosphere — A partially molten layer beneath the lithosphere that allows plate movement.
- Plate Boundary — The region where two tectonic plates meet, often marked by earthquakes and volcanic activity.
Action Items / Next Steps
- Obtain a blank world map and practice drawing the major tectonic plate boundaries using earthquake data.