Earth and Space Science / Unit 3: Plate Tectonics
3.5 The Theory of Plate Tectonics
Notes
Plate tectonics says the lithosphere is divided into plates that move slowly over the asthenosphere.
- Plates move a few centimeters per year, about as fast as fingernails grow.
- Driving forces: mantle convection, slab pull (a sinking plate edge pulls the rest along) and ridge push.
- There are about 7 major plates, including the Pacific, North American, Eurasian, African, South American, Antarctic and Indo-Australian plates.
- Most earthquakes and volcanoes occur along plate boundaries.
Practice
Plates move over which layer?
The weak asthenosphere allows plate motion.
Which is a driving force of plate motion?
Sinking dense plate edges pull plates.
Plates typically move at about:
Typical rates are 2-10 cm per year.
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