Understand the structure of earth and its internal processes. Know the ideas behind, and the evidence for, the theory of plate tectonics. Understand the mechanisms that cause plates to move. Understand the relationship between plate tectonics and natural hazards. Earth is layered: earth is layered and dynamic, the internal structure of earth can be considered in two fundamental ways: By composition, state and density or by strength. Melting forms magma but the other thing that is occuring as the oceanic crust is subducting under the continental crust: causes friction, like dragging sand paper together also can stick causes earthquakes** Different levels: step by step slides in pp. Inner core: solid, the middle part, 1300 km in thickness. High temperature, composed of iron, other stuff in there too but mostly iron. Outer core: liquid, 2000km in thickness, composition similar to the inner core just not as solid. The difference of having a liquid or solid centre matters greatly.