TECTONIC PLATES

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What is a tectonic hazard?
- A natural hazard caused by the movement of tectonic plates (e.g. volcanoes and earthquakes).
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Structure of earth - core
- Ball of solid (inner core) and liquid (outer core) iron and nickel.
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Structure of earth - mantle
- Around the core. - Semi-molten rock.
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Structure of earth - crust
- Outer layer of earth. - Divided into slabs (rigid segments) ('tectonic plates'), which can 'float' across the heavier, semi-molten rock (mantle) below.
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Continental crust
- Thicker (30-50km). - Less dense.
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Oceanic crust
- Thinner (5-10km) - More dense.
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Why do tectonic plates move?
- Due to convection currents in the mantle underneath the crust.
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Plate boundaries/margins
- The margin or boundary between two tectonic plates (where they meet).
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Destructive plate margins
-2 plates coming together (moving towards each other).-Where oceanic plate meets continental plate,denser oceanic plate is forced down into mantle and destroyed.-Volcanoes, earthquakes+ocean trenches.-2continental plates=both forced up=mountain range
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Example of destructive plate margin
- Along west coast of South America.
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Constructive plate margins
- 2 plates moving away from each other. - Magma (molten rock) rises from mantle to fill gap and cools, creating new crust.
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Example of constructive plate margin
- The mid-Atlantic ridge.
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Conservative plate margin
- 2 plates are moving sideways past each other, or are moving in same direction but at different speeds. - Crust isnt created or destroyed.
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Example of conservative plate margin
- Along west coast of USA.
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Formation of volcanoes at destructive plate margins
-Denser oceanic plate goes under continental plate.-Oceanic plate moves down into mantle, where its melted+destroyed.-Pool of magma forms.-Magma rises through vents(cracks in crust).-Magma erupts onto surface('lava').
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Formation of volcanoes at constructive plate margins
- Magma rises up into gap created by plates moving apart, forming a volcano.
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What does a volcano emit?
- Lava. - Gases. - Lots of ash, which can cover land, block out the sun and form pyroclastic flows (super-heated currents of gas, ash and rock).
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Formation of earthquakes at destructive plate margins
- Tension builds up when one plate gets stuck as it's moving down past the other into the mantle. - Shockwaves (vibrations) are sent out by the plates once they eventually jerk past each other (this is the earthquake).
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Formation of earthquakes at constructive plate margins
- Tension builds along cracks within the plates as they move away from each other. - Shockwaves (vibrations) are sent out by the plates once they eventually jerk past each other (this is the earthquake).
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Formation of earthquakes at conservative plate margins
- Tension builds up when plates that are grinding past each other get stuck. - Shockwaves (vibrations) are sent out by the plates once they eventually jerk past each other (this is the earthquake).
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What is the 'focus' of the earthquake?
- The point in the Earth where the earthquake starts. - The shockwaves spread out from the focus. - Nr the focus the waves are stronger and cause more damage.
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What is the 'epicentre' of the earthquake?
- The point on the Earth's surface straight above the focus.
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Reasons why people continue to live in areas at risk from a tectonic hazard
-Always lived there.-Employed in area.-Confident of governmental support after disaster.-Dont think earthquake/volcano will happen again in area.-Soil is fertile:full of minerals from volcanic ash/lava, so attracts farmers.-Tourist attractions:jobs.
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Management strategies - monitoring
-Seismometers and lasers monitor earth movements, and can be used in early warning systems for earthquakes. - Signs of a volcanic eruption can be monitored (e.g. tiny earthquakes, escaping gas and changes in volcano's shape.
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Management strategies - prediction
- Earthquakes cant be reliably predicted, but by monitoring movement of tectonic plates, scientists can forecast which areas should be prepared from one to occur. - Well-monitored volcano=eruption can be predicted - gives people time to evacuate.
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Management strategies - protection
-Earthquake-resistant buildings,e.g.special foundations that absorb earthquake's energy.-Strengthen existing buildings/bridges (e.g. wrap pillars in steel frames).-Automatic shut-off switches fitted to turn off gas+electricity supplies-prevent fires.
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Management strategies - planning
- Avoid planning future developments in areas most at risk from tectonic hazards. - Train+prepare emergency services. - Educate people so they know what to do. - Plan evacuation routes. - Stockpile emergency supplies.
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Other cards in this set

Card 2

Front

Structure of earth - core

Back

- Ball of solid (inner core) and liquid (outer core) iron and nickel.

Card 3

Front

Structure of earth - mantle

Back

Preview of the front of card 3

Card 4

Front

Structure of earth - crust

Back

Preview of the front of card 4

Card 5

Front

Continental crust

Back

Preview of the front of card 5
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