geography ✿ global hazards (tectonic)

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23 Terms

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continental crust

crust found underneath large land masses

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oceanic crust

crust found underneath the oceans. (ocean floor)

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epicentre

the Earth's surface directly above the focus

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focus

where the earthquake starts below the Earth's surface

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how deep under the crust are shallow-focus EQs?

0-70km

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how deep under the crust are intermediate EQs?

70-300km

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how deep under the crust are deep-focus EQs?

greater than 300km

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Describe what a hot spot is. [2]

an area of the earth’s crust where unusually high heat flow is linked to volcanic activity

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constructive plates

  • tectonic plates moving apart

  • both volcanic eruptions and earthquakes can occur here (Mid-Atlantic Ridge)

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destructive plates

  • tectonic plates move towards one another.

  • The oceanic crust is forced to sink, the continental crust rises above

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Conservative plates

  • tectonic plates move past each other

  • only earthquakes occur here

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Collison plates

  • two plates move towards each other

  • the crust is forced upwards forming fold mountains such as the Himalayas

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Convection currents

Hot currents that make plates move

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what are earthquakes caused by?

  • EQs occur at all plate boundaries

  • EQs happen when tectonic plates move, causing pressure and a sudden violent shake occurs

  • they can also occur when humans drill or mine into the crust

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Seismic waves

Shock waves from earthquakes

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what does a Richter scale measure?

the magnitude of earthquakes

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what are seismometers used to detect?

seismic waves from earthquakes

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what does the Mercalli scale measure?

the damage caused by earthquakes (1-10)

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Explain how the movement of tectonic plates at a destructive plate boundary causes volcanoes to form. [4]

  • The tectonic plates move towards each other and one plate is forced to subduct

  • this causes crust to melt due to friction

  • pressure in magma chamber builds up

  • molten material rises as it is dense

  • magma moves through cracks of the crust

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Volcanoes are formed on the margins ___________ and __________

Constructive and destructice

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State 3 features about composite volcanoes

  • found at destructive margins

  • most violent eruptions

  • lava is thick and heavy

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state 3 features about shield volcanoes

  • found at constructive margins

  • Not as violent eruptions

  • Lava is thin and runny

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Name the process that causes the Earth’s tectonic plates to move. [1]

convection currents