The Earth’s tectonic plates

1. The Earth’s tectonic plates

2. There are two types of crust: - Oceanic crust – denser and about 5km thick. Continental crust – lighter and about 30km thick.

3. Plate Boundaries The crust is made up of individual plates. These plates are constantly moving due to the hot convection currents that rise within the mantle. The movement of the plates has a great impact on the boundaries of the plates, but the middle area of the plates are relatively stable. Convection CurrentsLarge convection systems in the mantle may carry along the plates of the lithosphere like a conveyor belt.

4. Plates may move apart, move closer together or slide past each other. This may result in: - • Fold mountains • Volcanoes • Earthquakes • Rift valleys • Deep ocean trenches

5. Exercise – name the plates!!! Types of Plates

6. Compressional (destructive) plate boundary • Plates move together • One plate sinks below the other • The plate melts in the subduction zone where there is great pressure • Energy may be released as an earthquake • The molten rock or magma may rise forming composite volcanoes • The lighter crust at the surface may crumple to form fold mountains

7. Tensional (constructive) plate boundaries • Plates move apart • Gap filled by rising magma from the mantle • Rising magma forms shield volcanoes • Most common under oceans so submarine volcanoes or volcanic islands • Plates buckle to form ridges

8. Passive (conservative) plate boundaries • Plates slide past each other • May slide past each other the same direction ( and different speeds) or the opposite direction. • Pressure builds up until one plate gives way causing an earthquake • Can cause land to be crumpled or ridged • E.G. North American Plate/Pacific Plate – San Andreas Fault.

9. What is the likelihood of tectonic activity in the UK? • 2. Tectonic activity in Europe is concentrated in Iceland and southern Italy. State one tectonic similarity and one difference between Iceland and Italy. 3.