The document discusses the structure of the Earth and the theory of plate tectonics. It describes the Earth's layers including the inner and outer core, mantle, and thin crust. It explains that evidence such as matching fossil and rock patterns on continents support the idea that continents move and were once joined. It then outlines three types of plate boundaries: constructive boundaries where plates move apart causing volcanoes, destructive boundaries where one plate subducts under another causing volcanoes, and collision boundaries where mountains are formed when plates push together.

2. Cross section of the Earth

3. Inner Core Mantle Outer Core Crust The outer layer of the earth. It is a very thin layer ranging from 6-70km thick. Layer of liquid made up largely of iron. Due to the high temperature of this thick layer it has a consistency like jam! Temperatures range from 5000 0C near the core to 1300 0C just below the crust. This is a solid layer and is also made up if iron. Temperatures can reach 5,500 0C

4. Why do the plates move?

6. Continental drift

9. Constructive plate boundary At a constructive plate boundary, two plates move apart. As the two plates move apart, magma rises up to fill the gap. This causes volcanoes. However, since the magma can escape easily at the surface the volcano does not erupt with much force. Earthquakes are also found at constructive boundaries. An example of a constructive boundary is the Mid-Atlantic Ridge .

10. Destructive plate boundary A destructive plate boundary is found where a continental plate meets an oceanic plate. The oceanic plate descends under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is now hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface, the liquid rock forms a volcano.

11. Collision plate boundary Collision boundaries occur when two plates of similar densities move together (i.e. a continental plate and a continental plate). This causes the material between them to buckle and rise up, forming fold mountains. The Himalayas are an example of a chain of fold mountains. They have been formed by the Indian plate colliding into the Eurasian plate.

12. A good example of this type of motion is the San Andreas Fault which runs through California. PLATES MOVING SIDE BY SIDE