World Geography / Unit 2: Physical Geography
2.1 Earth's Structure and Plate Tectonics
Notes
Earth has four main layers: the thin solid crust, the thick mantle of hot, slowly flowing rock, the liquid outer core and the solid inner core.
- The crust and top of the mantle are broken into large tectonic plates that move a few centimeters per year.
- Divergent boundaries: plates move apart (Mid-Atlantic Ridge, East African Rift).
- Convergent boundaries: plates collide. Continent-continent collisions build mountains (India and Eurasia formed the Himalayas). When an ocean plate sinks under another plate (subduction), trenches and volcanoes form (the Andes).
- Transform boundaries: plates slide past each other, causing earthquakes (San Andreas Fault in California).
- The Ring of Fire around the Pacific Ocean has many of the world's earthquakes and volcanoes.
Practice
Which type of plate boundary formed the Himalayas?
The Indian Plate collided with the Eurasian Plate, pushing up the Himalayas.
Which layer of Earth is liquid?
The outer core is liquid metal; the inner core is solid.
The San Andreas Fault in California is where two plates slide past each other. What type of boundary is it?
Plates moving sideways past each other form a transform boundary.
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