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Tectonics The changing position of the continents is called continental drift. Plates move a few centimetres a year. Plate movement causes continents to collide, and split apart. The Earth’s crust is divided up into 7 large and 13 small plates. They float on the molten mantle. The plate boundaries are under extreme pressure and this is where most of the Earth’s earthquakes and volcanoes occur. Convection currents in the mantle cause the plates to move. Put the sentences in the correct order. They describe the process of PLATE TECTONICS. Tectonics The Earth’s crust is divided up into 7 large and 13 small plates. Plates move a few centimetres a year. They float on the molten mantle. Convection currents in the mantle cause the plates to move. Plate movement causes continents to collide, and split apart. The changing position of the continents is called continental drift. The plate boundaries are under extreme pressure and this is where most of the Earth’s earthquakes and volcanoes occur. Tectonics Plate Boundaries Tectonics Plate Boundaries Tectonics Plate Boundaries North American Eurasian Pacific Pacific African Nazca South American Indo-Australian Plate Antarctic Tectonics Plate Boundaries Tectonics Types of Boundary Types of Plates Continental crust is much thicker than Oceanic crust. As a result it has more force and can ‘push the Oceanic crust around’. Tectonics Types of Boundary Divergent Plate Boundaries At a divergent 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 divergent boundaries. An example of a constructive boundary is the Mid-Atlantic Ridge. Tectonics Types of Boundary Divergent Plate Boundaries Tectonics Types of Boundary Divergent Plate Boundaries mid-ocean ridge ocean mantle Tectonics Types of Boundary Convergent Plate Boundaries A convergent 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. Tectonics Types of Boundary Convergent Plate Boundaries Tectonics Types of Boundary Convergent Plate Boundaries F E A B D 1.oceanic plate C 2. The oceanic crust sinks under the less dense continental crust. 4. continental crust 5. explosive volcanoes 3. The oceanic crust melts and rises. 6. mantle Tectonics Types of Boundary Convergent Plate Boundaries Tectonics Types of Boundary Convergent Plate Boundaries 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 African plate colliding into the Eurasian plate. Tectonics Types of Boundary Convergent Plate Boundaries Tectonics Types of Boundary Conservative Plate Boundaries Conservative plate boundaries exist where two plates do not directly collide but slide past each other along a fault (weakness). No volcanoes are found along these plate boundaries, but earthquakes do occur. An example of such a boundary is the San Andreas Fault in California. Tectonics Types of Boundary Conservative Plate Boundaries Tectonics Where are what type of boundary? North American Eurasian Pacific Pacific African Nazca South American Indo-Australian Plate Antarctic