Plate Tectonics 1 of 26 Boardworks Ltd 2003

Plate Tectonics 1 of 26 © Boardworks Ltd 2003

Teacher’s notes and Flash files Most slides contain notes to accompany the presentation. This icon indicates that the notes contain particularly detailed instructions or extension activities. To access these notes go to ‘Notes Page View’ (Power. Point 97) or ‘Normal View’ (Power. Point 2000/2002). Notes Page View Normal View This icon indicates that a Flash file has been embedded into the Power. Point slide. These files are not editable. 2 of 26 © Boardworks Ltd 2003

How old is the Earth? The Earth is… 2 million years old 100 million years old 4600 million years old 3 of 26 © Boardworks Ltd 2003

Mark the following events on your time line. What do you notice? India collides with Asia – 50 m First flowers appear – 100 m Man (homo sapiens) inhabits the Earth – 0. 1 m Formation of the Alps – 30 m Dinosaur extinction – 65 m You were born! – 0. 00013 m Industrial Revolution (UK) - 0. 0001 m (figures are in ‘millions of years ago’) 4 of 26 © Boardworks Ltd 2003

Cross section of the Earth 5 of 26 © Boardworks Ltd 2003

Continental drift 6 of 26 © Boardworks Ltd 2003

Evidence for plate tectonics 1. Study of fossils – similar fossils are found on different continents. This is evidence that these regions were once very close or joined together. 2. Pattern of rocks – similar pattern of rock layers on different continents is evidence that the rocks were once close together or joined. 3. Shape of continents fit together like a jigsaw. Africa South America 7 of 26 © Boardworks Ltd 2003

Evidence for plate tectonics 4. Magnetic field pattern in iron containing rocks The reversal of the Earth’s magnetic field is recorded in the rocks that solidify at constructive margins. The symmetry around the margin is evidence that the rocks are moving apart. constructive margin SN S S S N N S N pattern same both sides 8 of 26 © Boardworks Ltd 2003

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Why do the plates move? Crust Convention Currents Mantle 10 of 26 © Boardworks Ltd 2003

Eurasian North American Pacific African Plate Nazca South American Indo Australian Plate Antarctic Plate Names 11 of 26 © Boardworks Ltd 2003

African. APlate Indo Australian Plate Boundaries 12 of 26 Can you name plates A and B? © Boardworks Ltd 2003

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Plate boundaries 14 of 26 link 1 link 2 © Boardworks Ltd 2003

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 at this type of boundary. 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. 15 of 26 © Boardworks Ltd 2003

Constructive plate boundary link 1 link 2 link 3 link 4 16 of 26 © Boardworks Ltd 2003

Mid-Atlantic ridge Sea Floor Spreading! Did you know that the ocean floor in the Atlantic is growing by 3 cm per year? Which of the following pairs of continents are moving further away from each other? 1) Europe and Africa 2) Europe and North America 3) South America and North America 17 of 26 © Boardworks Ltd 2003

How fast do plates move? The plates move at different rates. The Nazca and Pacific plates are moving apart at a rate of 18 cm per year while the Eurasian and North American plates are moving apart at a rate of 3 cm per year. To the nearest metre, how far will the Nazca and Pacific plates have moved over the next 200 years? 6 metres 18 of 26 36 metres 200 metres 928 metres © Boardworks Ltd 2003

A destructive plate boundary is found where a continental plate meets an oceanic plate. Destructive Plate Boundary 19 of 26 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. © Boardworks Ltd 2003

Collision Boundary 21 of 26 Collision boundaries occur when 2 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. © Boardworks Ltd 2003

Conservative plate boundaries exist where two plates do not directly collide but slide past each other along a fault (weakness). Conservative Boundary 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. 23 of 26 © Boardworks Ltd 2003

Attach labels to the correct part of the diagram. Outer core Crust Mantle Inner

Name this plate boundary A G B E C F D Match the labels to the letters Earthquakes occur due to friction The oceanic crust sinks under the less dense continental crust Oceanic plate Continental crust 26 of 26 Explosive volcanoes The oceanic crust melts and rises Mantle © Boardworks Ltd 2003

Constructive plate boundaries MID OCEAN RIDGE B A Oceanic Crust Mantle Where would you find older rocks – at A or at B? 27 of 26 © Boardworks Ltd 2003