The crust - oceanic crust (basalt) underlies the oceans and continental crust (granite) underlies land. Continental crust is less dense.
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Describe the inner and upper mantle.
Subjected to the core's heat, the rock of the inner mantle flows when acted on by forces. The upper mantle is cooler and breaks under stress.
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Why are convection currents formed in the mantle?
The core is hot due to radioactive decay. This heats the mantle which rises and cools before being sucked back down to form circular currents, which cause the overlying tectonic plates to move.
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What is seafloor spreading?
At divergent plate boundaries in the oceans, magma rises and hardens to form new oceanic crust. This pushes the plates apart causing the seafloor to expand (spread).
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What is palaeomagnetism?
The study of changes to Earth's magnetic field, which changes direction every 400,000 years. When magma cools to become rock the minerals line up with the current polarity.
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Has does palaeomagnetism support sea floor spreading?
There is the same pattern of magnetic direction either side of a mid oceanic ridge hence the rock was probably formed at the same time.
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What is subduction?
The destruction of tectonic plates as one slides under the other and melts in the subduction zone.
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What is slab pull?
As new formed crust cools it becomes denser and sinks into the mantle under its own weight, pulling the rest of the plate with it, a major driving force for plate movement.
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What are volcanoes?
Openings in the crust through which lava, gases and ash erupt. As pressure builds hot magma and gases in the mantle push up to the crust where they erupt.
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How many people are at risk from volcanoes?
500 million people from 1900 volcanoes
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What are earthquakes?
As plates move past each other they sometimes stick allowing pressure to build up. When it becomes too much, energy is releases in seismic waves from the focus. The epicenter is directly above the focus, where most damage occurs.
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Other cards in this set
Card 2
Front
Describe the inner and upper mantle.
Back
Subjected to the core's heat, the rock of the inner mantle flows when acted on by forces. The upper mantle is cooler and breaks under stress.
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