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geography > Plate Tectonics > Flashcards

Plate Tectonics Flashcards

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
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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.
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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

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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

case study: tohuku earthquake general information

A
  • in japan, which is part of the pacific ring of fire, so it is used to tectonic events
  • 11 march 2011
  • shallow focus: 32km
  • magnitude of 9.1
28
Q

tohuku earthquake 4 causes

A
  • destructive plate boundaries with pacific plate going under north american plate
  • epicentre was off the coast, 129km from sendai, so there was limited time to react and evacuate
  • caused a tsunami which was given a warning 12 mins after the earthquake and occurred 22 mins after earthquake
  • 100’s of aftershocks, including one with magnitude of 7.1, killing 4 people
29
Q

tohuku earthquake 6 primary impacts

A
  • thousands of buildings collapsed
  • 330,000 buildings deemed unsafe
  • over 2000 roads and railways collapsed, crushing cars and derailing trains
  • 56 bridges collapsed
  • people injured by falling objects
  • around 18,000 dead
30
Q

tohuku earthquake 6 secondary impacts

A
  • landslides in Miyagi
  • 10m high tsunami
  • cost of around $250 billion
  • increased dependency ratio
  • people made homeless
  • food and water contaminated by nuclear waste
31
Q

tohuku earthquake 4 responses

A
  • Pacific Warning Centre alerted affected countries and most people evacuated coastal areas
  • 70,000 people in the exclusion zone were evacuated
  • 120,000 people were evacuated later on
  • $150 billion was covered by government and insurance companies
32
Q

volcano case study: Mt Merapi general facts

A
  • active composite volcano in Java (SE Asia)
  • most active volcano in asia
    25 Oct - 30 Oct 2010
33
Q

Mt Merapi 5 causes

A
  • destructive plate boundary - indo-australian oceanic plate subducted below eurasian continental plate
  • volcanic bombs and heat clouds with temperatures up to 800C spread over a distance of 10km
  • pyroclastic flow travelled down 3km of heavily populated mountain sides (over 11,000 people)
  • volcanic ash fell up to 30km away and travelled 6km into the sky. Bronggang village was buried under 30cm of ash
  • sulphur dioxide blown across indonesia, as far south as Australia
34
Q

Mt Merapi 6 impacts

A
  • 350,000 people fled their homes
  • schools closed
  • roads blocked by abandoned vehicles
  • vegetable prices increased drastically as the crop yield was significantly reduced
  • heavy rain on 4 nov caused lahars, hampering relief efforts
  • 353 killed and 577 injured
35
Q

Mt Merapi 4 short term responses

A
  • 210 evacuation set up in schools, stadiums, etc
  • exclusion zone of 20km surrounding the volcano was established
  • Indonesian Disaster Management Agency mobilised volunteers to help
  • International aid was offered from governments and non-governmental organisations e.g. Red Cross
36
Q

Mt Merapi 6 long term responses

A
  • 2700 people moved to new and safer housing permanently
  • government made money available to farmers to replace livestock
  • government set up special task force to help those who were affected by volcano
  • ongoing exclusion zone of 2.5km
  • dams built in valleys to hold back lahars
  • improved prediction measures and improved education on evacuation

geography (14 decks)

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