Revision plate tectonic (landforms)
- 2. b. What is the internal structure of the earth?
- 3. Characteristics of the different earth structures Crust Mantle Core Temperature Nil 800-3000°C 3000- 5000°C Thickness About 70 km 2900km 3000 km Types of materials Basalt (Oceanic: 5- 8km) & Granite (Continental crust- 30-60km but less dense) Solid rocks Iron and Nickel Summary- It is thicker and hotter as it moves from the crust to the core.
- 4. Why do tectonic plate moves? • Convection current • Slab pull force
- 5. Why do tectonic plate moves? • Tectonic plates float on molten mantle, driven by convection currents. As the molten mantle materials is heated by the core, mantle expands, rises and spreads out, dragging the plates away from each other. •Subsequently, the hot molten mantle cools slightly and sinks, pulling the plates along. Hence plates move towards each other. •The sinking mantle material heats up again as it nears the core and the whole process repeats.
- 7. 2. Slab-pull force • Subduction occurs with the difference in density. An oceanic plate (denser) subducts under a less dense plate and pulls the rest of the plate along. • The subducting plate drives the downward- moving of the crust. d. Why do tectonic plates move?
- 8. Oceanic-Oceanic diverging • When two oceanic plates diverge, fractures are formed at the plate boundary. • Magma rises from the mantle to fill the gap between the plates. • New sea floor is formed when the magma cools and solidifies. • Magma rises at the zone of divergence to form the mid-oceanic ridge. • At various points along the ridge, magma builds up above the ocean to form volcanic islands.
- 9. Continental-continental diverging • When continental plates diverge, they are stretched, causing fractures to form at plate boundary. • Land in between 2 continental crusts sinks, forming a depression known as rift valley. *When the crusts on either side of the normal faults move apart, they sink and leave the central block standing higher than the rest, thus forming a block mountain.
- 10. 3.Oceanic-continental plate convergence • When an oceanic plate meets a continental plate, the denser oceanic plate subducts under the less dense continental plate. • A subduction zone forms, creating a deep oceanic trench along the plate boundary. • The subduction of the continental plate causes the soild mantle material to melt and magma is formed. e. What are the different types of plate boundaries?
- 11. 1. Oceanic–oceanic plate convergence • When two oceanic plates converge, one subducts under the other. • A subduction zone forms, creating a deep oceanic trench. • The subduction of the oceanic plate causes the solid mantle material to melt and magma is formed. • The magma rises through the mantle and ocean floor to emerge as volcanoes. • Eventually a chain or arc of islands called island arc is formed.
- 13. 2. Continental-continental plate convergence • However, both plates have similar densities and hence, resist subduction. • As a resist of the compressional force put against both plates, the plates break, slide along fractures in the crust, buckle and fold, forming fold mountains. • E.g. the Himalayas - convergence of the Indian Plate and the Eurasian Plate.
- 15. • When oceanic and continental converge, oceanic plate subducts under the continental. • A subduction zone forms, creating a deep oceanic trench. • The subduction of the oceanic plate causes the solid mantle material to melt and magma is formed. • The magma rises through the mantle and ocean floor to emerge as volcanoes. • The edge of thick continental plate buckles to form fold mountains. • Earthquakes may also occur. • E.g. the Australian Plate subducting under a section of the Eurasian Plate near Sumatra formed the Sunda Trench. 3.Oceanic-continental plate convergence e. What are the different types of plate boundaries?
- 16. Transform plate boundaries • Plates slide past each other. • As they do so, tremendous stress builds up. • This stress is eventually released, often as a violent earthquake. • E.g. San Andreas Fault, United States of America & North Anatolian Fault, Turkey e. What are the different types of plate boundaries?
- 17. Transform plate boundaries • Plates slide past each other. • As they do so, tremendous stress builds up. • This stress is eventually released, often as a violent earthquake. • E.g. San Andreas Fault, United States of America & North Anatolian Fault, Turkey e. What are the different types of plate boundaries?