Geography - Restless Earth

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What is the difference between Continental crust and Oceanic crust?
Continental crust is thicker and less dense, whereas oceanic crust is thinner and more dense
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What are the three types of plate margin?
Destructive, Constructive, and Conservative
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Describe what happens at destructive margins
When two plates move towards each other. Where an oceanic plate meets a continental plate, the denser oceanic plate is forced down into the mantle and destroyed. Where two continental plates meet, the plates smash together, no crust is destroyed
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Describe what happens at constructive margins
Where two plates move away from each other. Magma rises from the mantle to fill the gap and cools, creating new crust
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Describe what happens at conservative margins
Where two plates are moving sideways past each other, or are moving in the same direction but at different speeds. Crust isn't created or destroyed
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Describe the formation of fold mountains
They are formed when tectonic plates collide and the sedimentary rock that has built up between them are folded and forced upwards to form mountains. This happens at destructive margins
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How are volcanoes formed at destructive margins?
The oceanic plate subducts under the continental plate and is destroyed in the mantle. A pool of magma forms. The magma then rises through cracks in the crust called vents. The magma then erupts onto the surface forming a volcano
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How are volcanoes formed at constructive margins?
The magma rises up into the gap created by the plates moving apart, forming a volcano
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Name three types of volcano
Composite volcanoes, Shield volcanoes, and Dome volcanoes
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Describe a composite volcano
Made up of ash and lava that's erupted, cooled and hardened into layers. The lava is usually thick and flows slowly. It hardens quickly to form a steep-sided volcano
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Describe a shield volcano
Made up of only lava. The lava is runny. It flows quickly and spreads over a wide area, forming a low, flat volcano
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Describe a dome volcano
Made up of only lava. The lava is thick, it flows slowly and hardens quickly, forming a steep-sided volcanoo
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How can scientists predict a volcanic eruption?
Small earthquakes, escaping gas, and changes in the shape of the volcano (e.g. bulges in the land where magma has built up under it)
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Characteristics of a supervolcano
Flat, Cover a large area, and have a caldera
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Consequences of a supervolcanic eruption
Global. Will throw out thousands of cubic km of rock, ash and lava. A thick cloud of super-heated gas and ash will flow at high speed. Ash will shoot km into air and block out sunlight over whole continents, can tigger mini ice ages.
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Where do earthquakes occur?
At all three plate margins
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Describe how an earthquake occurs
Tension builds up between plates, however the plates eventually jerk past each other, sending out shock waves. The shock waves spread out from the focus. Near the focus the waves are stronger and cause more damage
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What is the focus of an earthquake?
The point in the Earth where the earthquake starts
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What is the epicentre of an earthquake?
The point on the Earth's surface directly above the focus
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Describe two ways of measuring Earthquakes
The Richter scale - measures the amount of energy released by the earthquake, called the magnitude. Another way is using the Mercalli scale, which measures the effects of the earthquake by asking eyewitnesses for observations
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How do supervolcanoes form at hotspots?
Magma rises up through cracks in crust to form magma basin below surface. Pressure of magma causes bulge on surface. Bulge eventually cracks, creating vents that lava, ash and rock escape through. Magma basin emties so bulge collapses. Caldera left
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Card 2

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What are the three types of plate margin?

Back

Destructive, Constructive, and Conservative

Card 3

Front

Describe what happens at destructive margins

Back

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Card 4

Front

Describe what happens at constructive margins

Back

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Card 5

Front

Describe what happens at conservative margins

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