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GCSE revision > Geography- Dangerous World > Flashcards

Geography- Dangerous World Flashcards

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0
Q

Draw and label a constructive plate margin

A
  • two oceanic crusts moving apart
  • cracks and fractures form between the plates, which gets filled with magma (basalt-runny) and forms new land
  • forms shallow sided volcanoes (shield volcanoes) and a mid oceanic ridge
  • small earthquakes
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1
Q

What are the four different types of plate boundary?

A
  • Constructive
  • Destructive
  • Collision
  • Conservative
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2
Q

Example of a constructive plate margin

A

Iceland on the mid Atlantic ridge (North American plate and Eurasian Oceanic plates are pulling apart)

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3
Q

Draw and label features of a collisional plate boundary

A
  • destructive plate boundary where two continental plates collide
  • forms fold mountains
  • Destructive earthquakes can happen at the fault (huge cracks in the crust) as energy build in collision zones
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4
Q

Example of a collisional plate boundary

A

The Himalayas, where the Indian and Eurasian continental plate push into each other

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5
Q

Draw and label a diagram of a destructive plate boundary.

A
  • When one plate is oceanic crust and the other is continental crust the denser oceanic plate subduct under the lighter continental crust when the plates push together.
  • The subduction zone is an oceanic trench.
  • the oceanic plate sinks there is great pressure and the oceanic crust is destroyed and it melts forming the magma to rise upwards leading to the formation of cone-shaped composite volcanoes.
  • The sinking oceanic plate can stick to the continental plate and pressure will build up.
  • When plates finally snap apart, a lot of energy is released as an earthquake. The earthquakes are often devastating, especially if shallow.
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6
Q

Example of a destructive plate boundary

A

Nazca plate is forced under the South American Plate.

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7
Q

Draw and label a diagram of a conservative plate boundary

A
  • when the plates slide past each other
  • moving in similar directions at slightly different angles and speed
  • they tend to get stuck which causes a build up of friction and pressure
  • eventually they snap causing a destructive volcano
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8
Q

An example of a conservative plate boundary

A

San Andreas fault in California, USA

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9
Q

Characteristics of the crust

A
  • outer layer of the earth
  • relatively thin
  • split into various plates that move
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10
Q

Characteristics of mantle

A
  • The layer between the outer core and the crust
  • dense and mostly solid (semi molten)
  • convection currents create the movement
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11
Q

Characteristics of the core

A
  • the centre of the earth

- split into the outer (molten) and inner core (solid)

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12
Q

Characteristics of oceanic crust

A
  • Denser
  • thinner (5km thick)
  • basaltic
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13
Q

Characteristics of continental crust

A
  • thicker (30 km)
  • less dense
  • granitic
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14
Q

What are ocean trenches?

A

Deep sections of the ocean, typically 5,000 to 10,000 metres

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15
Q

How are ocean trenches formed?

A

Oceanic plates sink below a continental plate (subduction zone is an ocean trench). One wall Is formed by the sub ducted ocean plate and the other by the overriding continental plate.

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16
Q

Where are the majority of ocean trenches?

A

The edge of the Pacific Ocean

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17
Q

Example of an ocean trench

A

The Mariana Trench- Pacific plate subduct beneath the Philippine plate

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18
Q

Describe the pattern of earthquakes

A
  • Usually occur in linear patterns along plate boundaries

- Most of them are found around the Pacific ring of fire (destructive plate boundary)

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19
Q

Describe the pattern of volcanoes

A
  • most volcanoes occur in narrow belts or are grouped together in small clumps because they usually occur at plate boundaries.
  • over half of the world’s volcanoes and earthquakes occur around the Pacific Ring of Fire (destructive plate boundary
  • occasionally volcanoes are found away plate margins, at hot spots.
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20
Q

Draw and label a diagram describing the formation of fold mountains

A
  • During long periods of quiet between Earth movements sedimentary rock, thousands of metres thick formed in big depressions called geosynclines. (Rivers carried sediments and deposited them in the geosynclines)
  • Over millions of years the sediments were compressed into sedimentary rocks such as limestone.
  • The sedimentary rocks were then forced upwards into a series of folds by the movement of the tectonic plates
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21
Q

What is an anticline?

A

Upfield of folded rocks

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22
Q

What is an syncline?

A

Down fold of folded rocks

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23
Q

What is an overfold?

A

Where a fold have been pushed over on one side

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24
Q

Where do shield volcanoes form?

A

Constructive plate margins

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25
Q

Draw and label a shield volcano

A
  • Some magma may be forced out to the surface through a vent.
  • cone with wide base and gentle slopes (~6’o)
  • made of lava only
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26
Q

Example of a shield volcano

A

Mauna Loa in Hawaii

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27
Q

Describe shield volcanoes lava and eruptions

A
  • basic lava (low silica) which comes from within the mantle
  • runny, flows long distances before cooling
  • eruptions regular and not violent
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28
Q

Where do composition volcanoes form?

A

Destructive plate boundaries

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29
Q

Draw and label a composite volcano

A
  • Made of alternate layers of lava and ash
  • Tall cone with narrow base and steep sides (30’o)
  • secondary cone
  • crater
  • main vent
  • magma chamber
  • pyro clastic flow
  • lava flow
  • ash cloud
  • volcanic bomb
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30
Q

Describe the lava of composite volcanoes and its eruptions

A
  • The eruptions are explosive but irregular with long dormant periods.
  • After an eruption the vent becomes blocked, which leads to great pressure building up before the next eruption.
  • During these eruptions lava is shattered into pieces so bombs, ash and dust are showered over a wide area.
  • the magma is high in silica, viscous and acidic
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31
Q

Example of a composite volcano

A

Mount Edna in Italy

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32
Q

Explain the formation of a composite volcano

A
  • The denser oceanic plate is pushed down below the lighter continental plate at a subduction zone.
  • In the subduction zone, the plate forms a pool of magma.
  • Great heat and pressure forces the magma along a crack where it erupts at the surface to build up a volcano.
  • The ash then falls on top to form a layer (alternate layer of ash and lava)
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33
Q

What is a Lahar?

A

Mudflows formed when surface water picks up volcanic ash and deposits it as mud

34
Q

What is a pyro clastic flow

A

Materials that move down the side of volcanoes (rocky debris and ash)

35
Q

What is a nueé ardente?

A

Fast moving cloud

36
Q

Describe the formation of a shield volcano

A
  • Magma rises upwards from the mantle to fill the gap.
  • This adds new rock to the spreading plates.
  • Some magma may be forced out to the surface through a vent.
37
Q

What is an extinct volcano?

A

A volcano that will never erupt again

38
Q

What is a dormant volcano?

A

Haven’t erupted for at least 2000 years

39
Q

What is an active volcano?

A

Erupted recently and is likely to erupt again

40
Q

What are the primary effects of an eruption?

A
  • People injured and killed
  • Buildings, property and farmland destroyed
  • Communications and public services (transport, electricity, telephones…) disrupted.
41
Q

What are the secondary effects of an eruption

A
  • Shortages of drinking water, food and shelter
  • Spread of disease from contaminated water
  • Economic problems from the cost of rebuilding and the loss of farmland, factories, tourism and other economic activities
  • Social problems from family losses and stress
  • Lahars
  • Loss of life is can occur because of falling debris, suffocation from poisonous gases or people being buried in mud flows (the heat of the eruption can melt snow causing mud flows).
  • some massive eruptions have had global effects e.g dust in the atmosphere can reduce world temperatures.
42
Q

What are the immediate responses of a volcanic eruption?

A
  • Evacuation from areas (directly before an eruption if it is predicted or afterwards)
  • Emergency services deployed
  • International aid sent – e.g. tents, bottled water, medical supplies
43
Q

What are the long term responses of a volcanic eruption?

A

Rebuilding settlements

Redeveloping economic activities that were affected such as farming and tourism

44
Q

Why do people live near volcanoes?

A
  • mining (cooled lava contains minerals e.g gold, silver, diamonds.
  • scientific research (monitor and assess volcanic risk, produce hazard maps, emergency plans)
  • geothermal energy (renewable)
  • tourism (brings jobs and industry e.g gift shops, restaurants)
  • farming (mineral and nutrient rich soils)
45
Q

List three ways of monitoring volcanoes

A
  • electronic tilt meters
  • satellites
  • past eruptions
46
Q

How are electronic tilt meters used to monitor volcanoes

A

Electronic tiltmeters (that work like a spirit level) measure very small changes in the profile of the mountain. Including small earthquakes, increases emissions of steam and gases, and the crater bulging.

47
Q

How are satellites used to monitor volcanoes?

A

satellites detect movement (as little as 1mm). Changes in temperature at the surface can be seen on satellite images. Before an eruption the gases being emitted from the vent change (increasing amounts of sulphur dioxide) and robots can be used to monitor changes.

48
Q

How are past eruptions used to monitor volcanoes?

A

the gap between the patterns of lava flows and ash movement give information about how a volcano is likely to behave.

49
Q

List three ways volcanic eruptions are prepared for

A

-organising evacuation of people and arranging supplies.
- Land use zoning
- hazard mapping
can be used to try to limit the impact on people.

Excerpt From: “Restless Earth Title.” v1.0. iBooks.
This material may be protected by copyright.

50
Q

List two ways volcanic eruptions can be controlled

A

-spraying the lava with cold water

Diverting the lava with concrete blocks

51
Q

What are super volcanoes?

A

Super volcanoes, are mega, colossal volcanoes that erupt at least 1000km of material.

52
Q

Where do super volcanoes occur?

A

At hot spots away from plate boundaries

53
Q

How do super volcanoes form?

A
  • Super volcanoes are formed when magma in the Earth, rises into the crust from a hotspot but is unable to break through the crust.
  • Pressure builds in a large and growing magma pool until the crust is unable to contain the pressure.
  • Cracks appear in the surface and gas and ash erupt from the magma chamber.
  • The magma chamber collapses, forming a depression called a caldera
54
Q

How does a super volcanic eruption affect the whole world?

A

There is so much dust in the atmosphere it can lead to a ‘volcanic winter’ – lower temperatures on Earth, because less sunlight reaches the surface.

55
Q

In what five ways are super volcanoes different to normal volcanoes?

A
  1. They are much bigger
  2. They emit huge amounts of material (at least 1000km3 compared to 1km3 when Mt St Helens erupted)
  3. They do not look like a volcano as they do not have characteristic cones
  4. They are large depressions called calderas and often have a rim of higher land around the edges
  5. They do not occur on plate boundaries/margins

Excerpt From: “Restless Earth Title.” v1.0. iBooks.
This material may be protected by copyright.

56
Q

When and where was the last super volcanic eruption?

A

Toba, 74,000 years ago

57
Q

What is an earthquake?

A

An earthquake is the shaking and vibration of the crust due to movement of the Earth’s plates (plate tectonics).

58
Q

Where do earthquakes occur?

A

Along any type of plate boundary

59
Q

How do earthquakes occur?

A
  • plates do not move smoothly - sometimes they get stuck.
  • When this happens a great deal of pressure and tension builds up.
  • When this pressure is eventually released, an earthquake tends to occur
60
Q

What is a focus point?

A

The point in the earth’s crust where the earthquake originates. The shaking is worse on the surface if the focus is shallow.

61
Q

What is the epicentre?

A

The point at the Earth’s surface directly above the focus.

62
Q

What are shock waves?

A

Seismic waves generated by an earthquake that pass through the Earth’s crust.

63
Q

What are the characterises of primary waves?

A
  • The first seismic waves to radiate out
  • they are relatively weak and cause the surface to move forward and backward in the direction of wave movement.
  • travel well below the surface
  • travel fastest
64
Q

What are the characteristics of secondary waves?

A
  • stronger waves
  • at right angles to the outward movement of the main wave.
  • travel well below the surface.
  • slower
  • There are transverse, which waves cause side-to-side movement which causes the most damage.
65
Q

How is the magnitude of an earthquake measured?

A

An instrument called a seismograph

66
Q

How do seismographs work?

A

Seismographs record the extent of shaking by a pen identifying the trace of movement on a rotating drum. The line graph produced is called a seismogram.

67
Q

What are characteristics of surface waves?

A
  • arrive later
  • strongest wave
  • longitudinal waves cause up and down movement and transverse waves cause side to side movement (lots of damage)
68
Q

What is the Richter scale?

A

The Richter scale is used for measuring earthquakes based on scientific recordings of the amount of movement.

69
Q

What scale does the Richter scale go up in?

A
  • It is a logarithmic scale. (This means there is a 10-fold increase every time the scale increases by 1. An earthquakes measured at 7 is 10 times stronger than one measured at 6 and 100 times stronger than one measured at 5.)
  • Earthquakes are given a number between 1 and 10 (although there is technically no upper limit to the scale.

Excerpt From: “Restless Earth Title.” v1.0. iBooks.
This material may be protected by copyright.

70
Q

What is the mercalli scale?

A

The Mercalli scale is used to indicate the intensity of an earthquake, using Roman numerals

71
Q

How are earthquakes measured on the mercalli scale?

A
  • It takes into account the visible (observed) effects on the Earth’s surface, people and buildings.
  • The number on the scale is based on a person’s observation.
72
Q

What are the primary effects of earthquakes?

A
  • Collapsing buildings, roads and bridges
  • people killed and/or being trapped
  • people injured, e.g falling building materials
73
Q

What are the secondary effects of earthquakes?

A
  • fires (caused by burst gas pipes and electrical wires falling down)
  • tsunamis (caused my earthquake on the sea floor)
  • landslides (most likely on steep slopes and ares of weak rock)
  • Diseases such as cholera spread easily when burst pipes lead to a shortage of fresh water.
74
Q

What physical factors of an earthquake lead to high amounts of damage?

A
  • High magnitude
  • shallow focus
  • sands and clays vibrate more
75
Q

What physical factors of a earthquake lead to low levels of damage?

A
  • small magnitude
  • deep focus
  • hard concrete floors
76
Q

What human factors lead to high amounts of damage from an earthquake?

A
  • high population density
  • self built houses (non earthquake proof)
  • lack of emergency procedures
77
Q

What human factors lead to low levels of damage from an earthquake?

A
  • low density of population
  • rural areas with list of open space
  • earthquake proof buildings
  • regular earthquake drills
78
Q

What are the three p’s?

A

Prediction
Protection
Preparation

79
Q

Name 4 features of an earthquake proof house

A
  • computer controlled weights on the roof to reduce movement
  • steel frames that sway during earth movement
  • fire resistant materials
  • foundations of house sunk into bedrock
80
Q

What is a tsunami?

A

a special type of wave where the entire depth of the sea or ocean is set in motion by an earthquake which displaces the water above it and creates a huge wave.

81
Q

How are tsunamis caused?

A
  • Tsunamis are caused by earthquakes at sea.
  • A tsunami forms when energy from an earthquake vertically jolts the seabed by several metres, displacing hundreds of cubic kilometres of water above the fault line
  • Large waves begin moving through the ocean, away from the earthquake’s epicentre.

Excerpt From: “Restless Earth Title.” v1.0. iBooks.
This material may be protected by copyright.

82
Q

How do the waves travel (deep water to shallow water)?

A
  • In deep water, the tsunami moves at great speeds.

- When it reaches shallow water near coastal areas, the tsunami slows but increases in height.

83
Q

What is one of the main signs a tsunami is going to hit?

A

The waterline suddenly retreats, exposing hundreds of metres and beach and seabed.

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