Dangerous Earth: a plate tectonic story

Ideas and Evidence in Science – a comprehension activity on plate tectonics

Learning objectives:

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several of the Earth’s tectonic plates move at about the same speed as fingernails grow – around 35 mm / yr

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plates are made of lithosphere (crust plus the upper part of the mantle)

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beneath the lithosphere is the asthenosphere, part of the upper mantle that is ductile because it contains 1-10% molten material as films

around the crystals

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the Earth’s magnetic field has ‘flipped’ (the N pole becoming the S pole, and vice versa) many times over geological time

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rocks magnetised in the direction of today’s magnetic field have normal magnetism, rocks magnetised when the field was the other way

round have reversed magnetism

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as tectonic plates move apart, new rock is formed and this ‘locks in’ the direction of the magnetic field at the time

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reading and written communication skills

Timing: 30 minutes

Pupils are to read and answer questions on the student's material text.