Plate Tectonics

Which type of plate is more dense, continental or oceanic?

Oceanic

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Describe a destructive plate margin

Continental and oceanic plates push together. The oceanic plate is forced down into the subduction zone. The continental plate is compressed to form fold mountains. Volcanoes also occur

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Describe a constructive plate margin

2 oceanic plates move apart to form shield volcanoes and new land

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Describe a conservative plate margin

2 plates move next to each other to cause earthquakes (San Andreas Fault)

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Volcanic Hazard - lava flow

Molten rock flowing down the sides of a volcano

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Volcanic Hazard - lahars

Mudflows, a mixture of ash and water (melted snow), travel at great speed down the mountain

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Volcanic Hazard - dust and ash clouds

Ash thrown high into the atmosphere shuts out sunlight and can completely bury buildings and crops when it settles

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Volcanic Hazard - pyroclastic flow

Burning clouds of ash and gas, with temperatures of 1000 degrees celsius, rush down the mountain, scorching everything

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Describe a shield volcano

Found at constructive plate margins. The lava is less viscous so can flow long distances before solidifying. Eruptions are gentle oozing so the lava forms large cone shaped mountains (eg. Surtsey in Iceland)

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Describe a composite volcano

Found at destructive plate margins. The lava is viscous so cools quickly and runs slow. Eruptions are explosive which is why they have a steep sided cone shape (eg. Mt St Helens in the USA)

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Describe the structure of an earthquake

The source of the earthquake is known as the focus. The point directly above the focus on the earth's crust is the epicentre.

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What are the factors that determine the impact of an earthquake?

1) distance from focus. 2) strength of earthquake. 3) nature of surface rock. 4) population of area. 5) preparation

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Why do people live in hazard zones?

1) scenery attracts tourists and brings income into area. 2) ash deposited leads to fertile soil. 3) geothermal energy. 4) volcanic rocks are good for building. 5) some people can't afford to move

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Case Study - Montserrat: what are the primary effects?

19 people died. Pyroclastic flow burnt buildings and trees. Ash buried over 2/3 of the island. 60% of housing was destroyed in capital, Plymouth.

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Case Study - Montserrat: what are the secondary effects?

Hospitals and schools closed. Farming became impossible due to ash. Coral reefs were destroyed by ash

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How do you predict an eruption?

Using remote sensing (satellites monitor temperature of volcano and gas emissions), seismometers (measure increase in volcanic activity), tiltmeters (monitor changes in shape of volcano) and ultrasounds (detect movement of magma)

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How do you prepare for an eruption?

1) exclusion zone around volcano. 2) authorities ready to evacuate. 3) emergency supplies. 4) good communication system. 5) people who could be affected informed

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How do you predict and earthquake?

Using laser beams ( detect plate movement), seismometer (monitor vibrations) and radon gas (escaped from cracks in surface prior to earthquake)

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How do you prepare for an earthquake?

1) people understand procedures. 2) emergency kits. 3) earthquake proof buildings. 4) reinforced roads/bridges

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Plate Tectonics

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