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Geography GCSE > The Restless Earth > Flashcards

The Restless Earth Flashcards

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1
Q

What is continental drift?

A

The theory that describes how plates have moved over millions of years.

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2
Q

What is plate tectonics?

A

The theory that describes the movements of the Earth’s surface (crust). It explains the distribution of fold mountains, earthquakes and volcanoes, and the process of continental drift.

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3
Q

What are the layers of the earth?

A

The inner core, the outer core, the mantle and the crust on the surface.

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4
Q

What cause the plates on the surface to move?

A

The sideways movement of rocks just beneath the crust.

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5
Q

What are the properties of oceanic crust? (in comparison to continental)

A

Newer - most less than 200million years old

Denser

Can sink

Can be renewed and destroyed

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6
Q

What are the properties of continental crust? (in comparison to oceanic)

A

Older, most more that 1500 million years old

Less dense

Cannot sink

Cannot be renewed or destroyed

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7
Q

Describe the process of convection current in the mantle

A
  1. Radioactive decay in the core heats the molten rock (magma)
  2. The heated magma rises as it becomes less dense.
  3. The magma moves away from the heat source and spreads out.
  4. The magma cools and starts to sink.
  5. The cycle of the convection cell restarts.
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8
Q

Describe what happens at a constructive plate boundary

A
  1. The plates are moving apart due to convection currents inside the earth.
  2. As the plates move apart, cracks and fractures form between the plates where there is no solid crust.
  3. Magma rises from the mantle and erupts at the surface of the earth in a volcano. Earthquakes also occur.
  4. The magma cools and solidifies to form a new crust of igneous rock. This process is repeated over millions of years.
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9
Q

What land forms are created at constructive place boundaries?

A

Rift valleys e.g. East African Rift Valley

Ocean ridge e.g. Mid Atlantic ridge (a series of underwater volcanoes)

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10
Q

Describe what happens at a conservative plate boundary

A
  1. At a conservative plate boundary, the plates are sliding past each other. They are moving in similar directions at slightly different angles and speeds. Because of this, they tend to get stuck.
  2. Eventually, the build up of pressure causes pressure to be released. This sudden release of pressure causes earthquakes.
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11
Q

What landforms are created at conservative plate boundaries?

A

Upland Ridge e.g. San Andreas fault - land is buckled and folded but on a smaller scale due to tension between the plates as they move past each other.

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12
Q

Describe what happens at destructive (subduction) plate boundaries

A
  1. Convection currents in the mantle cause the plates to move closer together.
  2. The oceanic plate is denser so, as they move together, the oceanic plate is forced underneath the continental plate. The point at which this occurs is the subduction zone.
  3. The oceanic plate melts to form magma and earthquakes are triggered due to friction.
  4. The magma collects to form a magma chamber and rises up through the cracks in the continental crust. As pressure builds up, a volcanic eruption can occur.
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13
Q

What are landforms created by destructive subduction?

A

Ocean trenches e.g. Mariana Trench.

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14
Q

What is an ocean trench?

A

A long, narrow depression of the sea floor caused by subduction at a destructive boundary.

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15
Q

Describe what happens at destructive collision boundaries

A
  1. If the two continental plates meet each other, they collide rather than one sinking beneath the other.
  2. The rocks buckle and fold upwards to form fold mountains
  3. Plates are the same density so little or no subduction takes place. Earthquakes also occur.
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16
Q

What are landforms created by destructive collision?

A

Fold mountains

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17
Q

What are fold mountains?

A

Highland areas formed along collision plate boundaries where great compressive earth movements take place

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18
Q

How are fold mountains formed?

A

Over millions of years from sedimentary rocks which have been forced upwards into a series of folds by the movement of tectonic plates.

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19
Q

Describe the process of the formation of fold mountains

A
  1. Rivers carry and deposit sediment into huge depressions in the sea called geosynclines.
  2. There are long periods of quiet between earth movement during which sediments, thousands of metres thick, build in these geosynclines.
  3. These sediments are then forced upwards into a series of folds by the compressive movement of tectonic plates.
  4. These sediments can be upfolds (anticlines) or downfolds (synclines). These rocks can also be fractured or faulted.
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20
Q

What are geosynclines?

A

Large scale depressions in the earths crust containing a thick series of sediments.

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21
Q

How do people use the Alps for farming?

A

On sunny south facing slopes - vineyards.

Dairy farming i.e. transhumance system (seasonal moment of animals) - summer: cattle taken high up to graze, crops grown on the valley floor because of the warm and fertile soil, winter: animals kept in sheds on the valley floor and fed summer crops.

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22
Q

How do people use the Alps for mining?

A

Salt, iron ore, gold, silver and copper were all mined but has dramatically decreased due to foreign sources.

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23
Q

How are the Alps used for hydroelectric power

A

The steep slopes, high precipitations and summer melting of the glaciers produce fast flowing rivers.

The narrow valleys are easy to dam and there are lakes to store water.

The cheap hydroelectric power is used by industries which require high input of electricity e.g. sawmills and electrochemicals.

Some electricity is exported to other regions to supply towns and cities Switzerland get 60% of its electricity from hydroelectric power stations in the Alps.

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24
Q

How are the Alps used for tourism?

A

Hundred million tourists visit the Alps each year.

Summer attractions include glacial lakes, scenery, walking, biking

Winter attractions include skiing, snowboarding, steep slopes, flat land on high Alps is easy to build on

New villages have been built

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25
Q

How have local people adapted to the conditions in the Alps?

A

Steep relief - goats are farmed because they have adapted to steep mountains, trees and man made defences use to protect against avalanches and rockslides

Poor soils - animals are grazed in most high areas as the soil isn’t great for growing crops

Limited communications:

Roads are built over passes (lower points between mountains) E.g. Brenner pass between Austria and Italy

Tunnels have been cut through mountains e.g. Mont blanc tunnel as it takes a long time to drive over passes and they can be blocked by snow

Electrified railways link the Alpine Valleys to cities e.g. Brenner and Saint Bernard.

Mountain cog railways, cable cars and chairlifts for skiers.

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26
Q

What is an earthquake?

A

A sudden release of energy or pressure from the earth’s crust that produces seismic shockwaves.

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27
Q

What is the focus of an earthquake?

A

The point where an earthquake originates - the shallower the focus, the more damaging and felt the earthquake is.

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28
Q

What is the epicentre of an earthquake?

A

The point of the Earth’s surface directly above the focus of an earthquake.

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29
Q

What is the Richter scale?

A

Measures the magnitude of an earthquake

No upper limit

Logarithmic scale

Quantitive measure

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30
Q

What is the Mercalli scale?

A

Measures the destructive power of an earthquake

1 to 12

Qualitative measure

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31
Q

What are the causes of earthquakes at a destructive (subduction) boundaries?

A

Pressure from subduction and melting

Broadbelt of earthquakes, depth increasing with distance from margin

Strong, high magnitude earthquakes

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32
Q

Causes of earthquakes at conservative boundaries

A

Pressure and tension builds up due to friction as the plates move past each other and get stuck

New zone of usually shallow depth earthquakes

Moderate to high magnitude of quakes, infrequent.

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33
Q

Causes of earthquakes at constructive boundaries

A

Tension from the gentle extension of the plates and margin

Earthquakes quite close to the centre and narrowly concentrated

High frequency but low magnitude earthquakes

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34
Q

What are primary effects of earthquakes?

A

The immediate effects that happen after the earthquake, these are most severe when there is a high population density in a developed area. e.g. building collapse, road damage, injuries/deaths.

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35
Q

What are the secondary effects of earthquakes?

A

The after effects such as fires, tsunamis, landslides and disease.

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36
Q

Factors affecting the effect of an earthquake:

A

Magnitude of the earthquake

Depth of the focus

Proximity of the epicentre

Geology

Land use

Time of the day

Housing/Building quality

Warning procedures

Education

Wealth of the country

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37
Q

How does geology affect the effect of earthquakes?

A

Weaker or more porous rock is more susceptible to liquefaction.

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38
Q

What caused the Christchurch earthquake?

A

New Zealand is located in the pacific ring of fire.

Strike slip movement east and west and upwards movement on a previously unknown fault line in south east Christchurch

39
Q

Christchurch earthquake basic info and location

A

5km depth, magnitude 6.3, 22nd February 2011, 12:51pm

Christchurch is located on the southern island of New Zealnd

40
Q

What is GeoNet?

A

A national network of instruments and data centres.

This detects and monitors earthquakes and provides info to emergency services almost immediately after an earthquake.

41
Q

Protection strategies in the Christchurch earthquake:

A

Part of the AMI stadium was reinforced by a vast network of 10m stone columns covering an area of 1200m2 - but this was not enough to protect subsidance of the stands by approx. 40cm. They are now considering driving piles down 25m to reach solid ground.

NZ has a building code for earthquakes - resistant buildings since 1935. Older buildings have not been reinforced on the South island as it is less earthquake prone, so are more vulnerable.

42
Q

Preparation strategies in Christchurch

A

Geonet organises public education about earthquakes and a campaign that encourages people to ‘Quakesafe’ their homes.

GeoNet provides earthquake insurance for home owners as the insurance companies can’t afford to.

43
Q

Primary impacts of Christchurch earthquake

A

70% of the buildings in the CBD were demolished

222,000 homes were affected (many uninhabitable)

181 people killed

Significant slope failure in upland Port Hills area - rock and debris

44
Q

Secondary impacts of the Christchurch Earthquake

A

Big decline in electronic payments because of damage to ATMs

Communities broken apart as people are forced to move elsewhere

13 schools closed, 18 merged, 4500 pupils lost due to out migration

15% fewer exports went through Christchurch airport in October 2012 compared to the previous year.

45
Q

Immediate responses of Christchurch EQ?

A

CBD of Christchurch was evacuated

Becuase of the ATMs, additional cash was vital - NZ $150mn cash was sent to christchurch on the week following the EQ.

The government established the Canterbury Earthwuake Recovery Authority to start the reconstruction of the city.

46
Q

Longterm responses of Christchurch EQ?

A

The Christchurch Central Recovery Plan set out the way in which the central area of the city would be redeveloped.

Nearly NZ$1 billion of planning consents were granted in the first 6 months of 2012, to help people rebuild their homes and livelihoods.

The government intends to spend NZ$1 billion in the next 10 years renewing the education system in the affected areas.

47
Q

Causes of the Haiti Earthquake?

A

A conservative fault runs through Haiti between the Carribean plate and the North American plate. It was caused by the release of pressure between the two plate. The Carribean plate was moving eastward from the North American plate.

It caused a strike-slip fault - where two sections fo Earth’s crust are grinding past each other in opposite directions.

48
Q

Earthquake info Haiti EQ and location

A

Magnitude 7, 9.97km depth, 4:53pm, 10km southwest from the capitcal Port-au-Prince, January 12th 2010

GDP$1300

Haiti is located in Central America in the Caribbean

49
Q

Primary impacts of Haiti EQ

A

105,000 houses destroyed, over 188,383 badly destroyed

Roads and docks in Port-au-Prince destroyed, difficult to deliver food, clean water, clothes and medicine

19 million m2 of rubble and debris in Port-au-Prince

Over 220,000 deaths

50
Q

Secondary impacts of Haiti EQ

A

Disease due to no clean drinking water and rotting dead bodies - cholera outbreak, 5899 killed, 216,000 infected.

4000 schools damaged or destroyed

1.5 million living in homeless camps

People trying to rebuild houses without the availability of money and materials

1 in 5 jobs lost due to the EQ

51
Q

Immediate responses to the Haiti EQ

A

Many countries responded to the appeals for aid - money, rescue and medical help - British public declared £107m

Rescue and aid efforts were slowed by the damage of communication systems, tranport (air, land and sea), hospitals and electrical networks

Further delay - confusion over who was in change, air traffic congestions and problems with prioritization of flights

Morgues overwhelmed in Port-au-Prince 10,000s of bodies having to be buried in mass graves

1.3m put into homeless shelters

52
Q

Long term responses in the Haiti EQ

A

1000s of EQ affected families were provided with agricultural asistance including 4,000 tonnes of crop seeds

1 million children recieve daily meals through the National School Feeding Programme

The EU gave $330m and the world banc concluded the country’s debt repayments for 5 years

The Senegalese offered land in Senagal to any Haitians

As of June 2011, 1.2 m people had benefited from water provision receiving more than 4,200m3 of water daily

Nearly 500,000 people have been provided with improved temporary shelter

6 months after the EQ, 98% of rubble remained uncleared, some still blocking the access roads.

53
Q

What is a tsunami?

A

A special type of wave, where an event, often an earthquake, moves the entire depth of water apart.

54
Q

Causes of tsunamis (4)

A

Earthquakes

(Submarine) Landslides

(Submarine) Volcanic eruptions

Meteorite impacts in the ocean

55
Q

How do tsunamis form?

A
  1. Tectonic upthrust (e.g. earthquakes) causes a vast quantity of water to be displaced in a very short space of time generating a huge amount of energy
  2. In the open sea, tsunamis travel up to 800km per hour and commonly go unnoticed as they pass beneathe ships because they are usually less than 1m high and the distance between wave crests is typically 100s of kilometres.
  3. As the tsunami approaches the coastline, they are slowed dramatically by friction to around 40 km/h. The wavelength becomes shortened and the wave amplitude increases. One of natures warning signs of a tsunami is the sudden withdrawal of the sea from a coastal region.
  4. Finally with the wavelength compressed and heightened to 5-10m the wave collides with the shore causing huge damage. Tsunamis consist of a series of waves that surge on shore for as long as 30 minutes. The succeeding outflows continues the destruction causing more damage to people and property. Furthermore, after the first wave hits, more waves follow at 20-60 minute intervals.
56
Q

Location of Tohoku tsunami

A

North East Japan, the Tohoku tsunami was caused by an earthquake in the Pacific Ocean

57
Q

Causes of Tohoku tsunami

A

Japan is at the centre of 4 plates with destructive subduction and conservative boundaries. Earthwuake occured on the subduction zone between the Pacific Plate and Okhotsk Plate

15-45 minutes after the earthquake struck, it caused tectonic upthrust and a large quantity of water was displaced, causing a tsunami that hit the east of Japan

58
Q

Japan EQ and Tohoku tsunami information

A

Magnitude 9.0, 11th March, 2:46pm

Tsunami height” 5 - 20m, max vertical shift almost 40m

59
Q

Primary impacts of Tohoku tsunami

A

16,000 known deaths

3000 people missing

130,000 buildings destroyed, twice as many damaged

Rikuzentahaka - 8368 buildings destroyed

Ishonomaki - at Okawa Elementary School 74/108 children and 10/14 teachers died

Estimated 26.7mn tonnes of debris

60
Q

Secondary impacts of Tohoku tsunami

A

Water flooded water-cooling systems at Fukushima Daiichi nuclear power plant - systems failed, 3 nuclear units experienced meltdown

  • caused immediate evacuation of the area within 20km

Damage caused by harmful pollutants that were emitted

Expected acceleration of ageing, low fertility and outmigration of population

61
Q

Immediate responses of Tohoku tsunami

A

Search and rescue and stabilisation and prevention of further nucleur disaster by Japanese government

Operation USA - sent shelter and medical supplies

  • first shipment of a $1.1m donation of Gap brand winter clothing was distributed to 10,000s of people in Miyagi, Fujushima and Iwate for the cold winter weather following the disaster.
62
Q

Long term responses of the Tohoku tsunami

A

Naoto Kan commissioned a report for the three principles of recovery: safety, sustainability and compassion.

It took 11 months to establish the Reconstruction Agency due to political infighting

The Reconstruction Agency established with these policies:

  • focus on local communities and human linkages within Japan
  • base survival on ‘self aid’
  • develop conditions for mutual and public aid
63
Q

What is a volcano?

A

An opening or vent in the Earth’s surface through which material (magma, gas, ash) erupts. They are a tectonic hazard.

64
Q

What is a hotspot? What does it cause?

A

A volcanic hotspot is an area in the mantle from which heat rises as a thermal plume from deep in the Earth.

High heat and lower pressure at the base of the tectonic plate facilitates melting of the rock

This melt, called magma, rises through the cracks and erupts to form volcanoes.

65
Q

What are the three states of volcanoes?

A

Active - one that has erupted in the last 10,000 years

Dormant - one that hasn’t erupted in the past 10,000 years but which is expected to erupt again

Extinct - one that nobody expects to ever erupt again

66
Q

Main features of a volcano and what they are

A

Crater - created after an eruption where the top is blown off the volcano

Main vent - the main outlet for the magma to escape

Secondary vent - smaller outlets through which the magma escapes

Magma chamber - a collection of magma inside the Earth below the volcano

67
Q

Features of a composite volcano

A

Found on destructive (subduction) boundaries

Violent explosivity

Rare

Hazards: pyroclastic flows, lahars

68
Q

Formation of composite volcanoes

A

Describe what happens at destructive subduction boundary.

Made up of ash and lava that is erupted, cooled and hardened into layers. The lava is usually thick and flows slowly. It hardens quickly to form a steep sided volcano.

69
Q

Charcteristics of a shield volcano

A

Found on constructive boundary

Gentle explosivity - limited pressure

Frequent

Hazards: gases and lava flows

e.g Mauna Loa, Hawaii

70
Q

Formation of shield volcanoes

A

At constructive margins the magma rises up into the gap created by the plates moving apart.

The lava is runny, so flows quicly and spreads over a wide area, forming a low, flat volcano.

71
Q

Characteristics of dome volcanoes

A

Made of only lava

Lava is thick, it flows slowly and hardens quickly forming a steep sided volcano

72
Q

What are pyroclastic flows?

A

Hot volcanic ash and rock and hot expanding gases move at tremendous velocities - up to 300km/h.

73
Q

What are lahars?

A

Ash is liquified by rain or snow melt, hot or cold mudflows, 100 km/h

74
Q

What is volcanic gas?

A

Harmful gases can be emitted like CO2, SO2, Radon, killing people and other living things

75
Q

Primary effects of volcanoes?

A

Destruction of wildlife and vegetation

Deaths and injuries

Damage to infrastructure

Immediate decline in tourism

76
Q

Secondary effects of volcanoes?

A

Greenhouse gases contribute to global warming

The ash causes soil to be fertile

Acid rain

Ash cloud can cause global disruption

Can attract tourists

Permanent evacuation due to covering of ash

Disruption to transport

77
Q

Why do we predict volcanic eruptions?

A

To minimise damage

78
Q

Ways that scientists predict volcanic eruptions

A

Scientists can monitor the tell-tale signs that come before a volcanic eruption - tiny earthquakes, escaping gas from the vent eg SO2, changes in the shape of the volcano (bulges where the magma has built up)

Past frequencuy of eruptions and the gap between them

Tiltmeters can identify small, subtle changes in the landscape

79
Q

Location of the Eyjafjallajokull volcano

A

Located in Iceland, an island located immediately south of the Arctic circle

80
Q

Tectonic setting of Iceland

A

It sits on the mid atlantic ride, the conservative plate boundary between the Eurasian and North American plates - these plates move apart a few cm a year

This produces volcanic rift zones, where magma rises up, and where it reaches the surface, erupts as lava and ash

Iceland is also located on a hotspot so is seismically active for that reason

81
Q

Specific causes of the Eyjafjallajokull eruption

A

Fissure eruption. the eruption occured from linear fissures that run parallel to the volcanic rift zone.

The summit crater punched through the ice cap, causing cold meltwater to mix with magma, cooling it rapidly

This caused the magma to fragment explosively into a large quantity of very fine ash that was ejected into the atmosphere

82
Q

Negative primary impacts of the Eyjafjallajokull eruption

A

150m thick ice cap melting, 8000 people evacuated from flooding

20 farms destroyed by flooding and ash

Ash blocked out - sun turned day to night

Local water supplies contaminated with fluoride

Ash cloud - 6 flightless days - 17000 flights/day cancelled

83
Q

Postive primary impacts of the Eyjafjallajokull eruption

A

Temporary reduction in aircraft noise

2.8m tonnes less of CO2 emitted

No deaths

84
Q

Secondary negative impacts of the Eyjafjallajokull eruption

A

Ash silted rivers and caused blockages one year later

Shares in air travel and tourism agencies decreased by 4%

Meltwater produced caused a road to be breached in order to protect a bridge

Closed European airspace - in Kenya, farms depend on air transport to export vegetables and flowers to Europe - unable to be transported, food crops perished, farming operations halted

85
Q

Secondary positive impacts of the Eyjafjallajokull eruption

A

Boost to Iceland’s tourism - visitor centre opened near volcano

10% increase for avis in cross-border hire car demand

86
Q

Immediate responses to Eyjafjallajokull eruption

A

800 people evacuated from homes and villages (BUT NO DEATHS)

Rescuers wore face masks to prevent them from choking on the dense cloud of ash

87
Q

Long term responses to the Eyjafjallajokull eruption

A

EU funded a project called FutureVolc to install sensors to allow for real-time data analysis:

  • the monitors can detect minute movements or tremors within the ground and detect any curving of the Earth’s surface around the volcano which could indicate magma build up
  • other sensors will look for changes in gas emissions from active sites which could suggest movement of magma up through the Earth’s surface

Easyjet and Airbus are currently testing systems that it says will enable planes to detect and circumnavigate ash clouds

88
Q

What is a supervolcano?

A

A mega collosal volcano that erupts at least 1000km3 of material

89
Q

Where are supervolcanoes located?

A

Destructive plate margins and hotspots e.g. Yellowstone, USA

90
Q

How does a supervolcano form?

A

1) Rising magma cannot escape, and a large bulge appears on the surface
2) The bulge eventually cracks, creating vents for lava to escape through. Lava erupts out of the vents, causing earthquakes and sending gigantic plumes of ash and rock into the air.
3) As the magma basin empties, the bulge is no longer supported, so it collapses (spewing out more lava) - this forms a large depression called a caldera.

91
Q

Characteristics of supervolcanoes/how they are they different to volcanoes

A

They are flat with large depressions called calderas, often marked by a rim of higher land around the edges - volcanoes are like mountains, cone-shaped with a crater.

They cover a much larger area - much bigger than volcanoes.

They emit at least 1000km3 of material - volcanoes erupt more like 1km3.

They erupt less frequently, eruptions are 100,000s years apart

92
Q

Likely effects of a supervolcanic eruption

A

Local/National: A thick cloud of super heated gas and ash will flow at high speed from the volcano, killing, burning and burying everything it touches. everything within 10s of miles will be detroyed.

The ash will also settle over 100s km2, burying fields and buildings (ash from normal volcanoes usually covers a couple of km2)

Global: Ash will shoot into the air and blockout almost all daylight over whole continents. this could trigger a volcanic winter as less heat energy from the sun gets ot the earth.

Difficult to grow food, crops fail, plants can’t photosynthesise

People emigrating - migration crisis

Material will reach countries thousands of km away within 5 days

93
Q

What are shock waves?

A

Vibrations (the earthquake)

Shock waves spread out from a focus, near the focus the waves are stronger and cause more damage

Geography GCSE (11 decks)

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