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geography > Plate Tectonics > Flashcards

Plate Tectonics Flashcards

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1
Q

what is a volcano?

A

a volcano is formed when magma erupts onto the earth’s surface as lava through the vent in the earth’s crust

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2
Q

features of a volcano

A
  • lava
  • pyroclastic flow
  • ash
  • lahars
  • vent
  • secondary cones
  • crater
  • magma chamber
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3
Q

what is lava?

A

Magma that reaches the surface

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4
Q

what is pyroclastic flow?

A

Clouds of mixed poisonous gases and ash

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5
Q

what is ash?

A

Very fine-grained volcanic material

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6
Q

what are lahars?

A

Snow and ice melt and combine with the ash, creating lahars.

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7
Q

what is a vent?

A

Central tube through the volcano

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8
Q

what are secondary cones?

A

Eruptions from other vents lead to the formation of secondary cones on the sides.

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9
Q

what is the crater?

A

bowl-shaped basin at the top of the volcano

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10
Q

what is the magma chamber?

A

A large underground pool of magma

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11
Q

how do volcanoes form?

A
  • magma rises through cracks in the earth’s crust
  • pressure builds up (inside earth)
  • pressure and tension are released → plate movement
  • magma explodes to the surface, causing an eruption
  • lava cools and forms a new crust
  • over time, rock builds up, and new crusts form on top, forming a volcano
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12
Q

environmental impacts of volcanoes

A
  • pyroclastic flow
  • lava flow
  • volcanic bombs
  • laharas
  • earthquakes
  • landslides
  • tsunami
  • acid rain
  • ash fallout
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13
Q

human impacts of volcanoes

A
  • loss of life and injury
  • collapse and destruction of buildings
  • transport network damaged
  • loss of jobs and businesses
  • loss of crops
  • power and water supply damaged
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14
Q

opportunities of volcanoes

A
  • fertile soils - cooled lava contains minerals, leading to a high yield of crops
  • tourism - many people want to visit the area and study it
  • minerals and precious stones - can be sold, providing more work and income
  • geothermal energy - the magma gives out heat, which can be used to generate geothermal energy
  • creating new land areas - once the lava and ash cool forms new fertile land
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15
Q

stages of volcanoes

A
  • active: has erupted recently and is likely to erupt again
  • dormant: has not erupted recently but may in future
  • extinct: no evidence to erupt again
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16
Q

what are the two types of volcanoes?

A
  • shield volcanoes
  • composite volcanoes
16
Q

what is a shield volcano?

A
  • basaltic lava
  • low in height, gently sloping sides with a broad base
  • low silica content (covers long distances)
  • frequent eruptions but low in magnitude
  • high temperature
  • low gas content
    There is little build-up pressure.
16
Q

how do eruptions occur at constructive boundaries?

A

At constructive boundaries, plates move away from each other; magma rises to fill the gap

16
Q

what is a composite volcano?

A
  • andesitic lava
  • high in height, steep-sided volcanic cones
  • high silica content (covers short distance)
  • rare eruptions but in high magnitude
  • low temperature
  • high gas content
  • enormous build-up pressure
16
Q

how do eruptions occur at destructive boundaries?

A

At the destructive boundary, oceanic crust melts from friction and heat from the mantle, newly formed magma is lighter, so it rises to the surface

17
Q

what is a hotspot?

A

an area of the Earth’s mantle from which hot plumes rise upward, forming volcanoes on the overlying crust

17
Q

how do earthquakes occur?

A
  • tectonic plates move; they strike.
  • pressure and tension build up as the plates try to move.
  • eventually, they jolt free and pressure and tension are released inside the crust as energy.
  • the energy passes through the earth’s crust as waves, an earthquake
17
Q

what is an earthquake?

A

a sudden violent shaking of ground followed by a series of vibrations or movements in the earth’s crust

17
Q

what are the features of an earthquake?

A
  • focus
  • epicentre
  • convection currents
  • subduction zone
  • magnitude
17
Q

what are the effects of earthquakes?

A
  • a large number of deaths
  • fires breaking out
  • water pipes burst
  • water contamination, diseases
  • corpses: human & animal
  • accessibility difficult
  • building damaged/destroyed
  • tsunami can follow
  • reconstruction costs
17
Q

how can earthquakes be predicted?

A
  • measure earth tremors, pressure and release of gas
  • use maps and facts to find patterns in time/location
  • unusual animal behaviour
  • seismometer
  • richter scale
18
Q

how can people prepare for an earthquake?

A
  • build earthquake proof buildings
  • train emergency services
  • set up a warning system
  • create an evacuation plan
  • emergency food supply
  • prepare earthquake kit
19
Q

features of an earthquake proof building

A
  • computer controlled weights on the top to reduce movement
  • ‘birdcage’ interlocking steel frame
  • steel frames which can sway with quake movements
  • automatic window shatters to prevent falling glass
  • open areas for people to assemble when evacuated
  • foundations sunk into bedrock avoiding clay
  • rubber shock absorbers to absorb earths tremors
20
Q

what are the major tectonic plates?

A
  • Nazca
  • North American
  • South American
  • African
  • Eurasian
  • Indian
  • Australian
  • Antarctic
  • Pacific
21
Q

what is a collision plate boundary?

A

it occurs when two continental plates move towards each other
e.g. Indo-Australian and the Eurasian plate

22
Q

what is a constructive/divergent plate boundary?

A

it occurs when two plates move away from each other e.g. North American and Eurasian Plate

23
Q

what is a conservative/transform plate boundary?

A

it occurs when two plates slide past each other e.g. North American Plate and the Pacific Plate

24
Q

what is a destructive/ subduction/convergent plate boundary?

A

it occurs when an oceanic plate subducts a continental plate e.g. Pacific plate and the Eurasian plate‎

25
Q

what is the structure of the earth?

A
  • crust
  • mantle
  • outer core
  • inner core
26
Q

what are the two types of crust?

A
  • the oceanic crust which is thinner (5-10km) but heavier and denser
  • the continental crust which is thicker (25-90km) but is older and less dense
  • the oceanic crust is continually being created and destroyed due to plate movement, where it is denser and subducts under the continental crust.
27
Q

earthquake case study: Christchurch, New Zealand (causes, effects and management)

A
  • 22nd February 2011 at 12.51pm.
  • New Zealand is located on the plate boundary between the Australian (continental crust) and Pacific plates (oceanic crust).
    CAUSES
  • 22nd February 2011 at 12.51pm.
  • New Zealand is located on the plate boundary between the Australian (continental crust) and Pacific plates (oceanic crust).
  • the plate boundary moves in two ways- destructive and conservative.
  • the epicentre was 10km away from Christchurch; the second highest populated city in New Zealand
  • magnitude 6.3 on the Richter scale with a shallow-focus earthquake (5km below the surface)
    IMPACTS
  • 181 people were killed; over half of deaths occurred in the 6-storey Canterbury Television building when it collapsed and caught fire.
  • approximately 2000 people were treated for minor injuries.
  • 80% of the city was without electricity.
  • although many buildings did not collapse, some were demolished because they were unsafe. 10,000 houses would need to be re-built.
  • could no longer host Rugby World Cup
  • overall economic cost = NZ$ 3.5billion
    MANAGEMENT:
  • a full emergency response plan was in place within 2 hours of the earthquake happening
  • the Australian and New Zealand police enforced cordons and organised evacuations
  • 27,000 chemical toilets were flown into the area as sanitation and sewerage works were damaged.
  • insurance companies paid $898 million in building claims.
  • text message alert systems in place.
  • buildings reinforced with flexible steel that moves with the ground during an earthquake
  • use of monitoring equipment to detect movement of plates
28
Q

volcano case study: Eyjafjallajökull, Iceland (causes, impacts and management)

A

CAUSES
- Iceland is located on the Mid-Atlantic Ridge.
- the North-American and Eurasian plates move apart- called constructive plates.
- the disruption caused by Eyjafjallajökull was the result of a series of small volcanic eruptions, starting on the 20th March and ending in the October of 2010
IMPACTS
- the 150m thick ice cap melted, which caused major flooding to much of Iceland’s infrastructure.
- 0 reported deaths.
- airspace closed across Europe, with at least 17,000 flights a day being cancelled.
- the eruption cost insurers £65million to customers with cancelled flights.
MANAGEMENT
- the emergency services were prepared with advanced equipment.
- Iceland had a good warning system with texts being sent to residents with a 30-minute warning.
- large sections of European airspace were closed down due to ash spreading over the continent.
- Eyjafjallajökull has often triggered her larger sister volcano Katla to erupt after. As a result, scientists are monitoring her closely.
- insurance companies and airlines have reviewed their policies to customers.
- some airlines have built ash monitoring equipment onto their aircraft for safety.

geography (3 decks)

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