1. Changes Within the Earth
Geography

2. The Earth’s Layers
Core – center of the earth, consists of very hot metal
Mantle – a thick layer of rock around the core, mobile
Crust – rocky surface layer of the earth, thin like frosting on a cake

3. The Earth’s Layers

4. Plate Techtonics
Lithosphere – the surface features of the earth, including soil, rocks, and landforms
The lithosphere is broken into a number of moving plates
Plates vary in size and thickness
They slide over a hot and flexible layer of mantle
The earth’s oceans and continents ride atop the plates as they move

5. Plate Tectonics
Most earthquakes, volcanoes, and other geologic events occur along plate boundaries

6. Subduction and Convergence
Convergence – a collision of plates
Subduction – when one plate meets another and the lighter plate slides below the denser (more solid) plate
Oceanic plates are more dense than continental plates

7. Convergent Boundary – Oceanic/Continental
As the oceanic plate sinks the rock it is made of melts. Some of this will cool.
Effects: Volcanoes made from eruptions of the melted plate that did not cool

8. Cascade Mountains

9. Convergent Boundary – Oceanic/oceanic
The denser plate slides beneath the other
Effect: an arc of volcanic islands may form around the plate boundary

10. Japan

11. Convergent Boundary – Continent/continent
When two continental plates collide neither will sink
Convergence is slow and violent
Effect: Spectacular mountain ranges

12. The Himalayas
Still colliding at a rate of about 2 inches per year