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Geography > Restless Earth > Flashcards

Restless Earth Flashcards

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1
Q

CASE STUDY- Earthquake- MEDC

A

Chile

2010

On a destructive plate margin - on boundary between Nazca and South American plates

500 people killed

some bridges and roads were destroyed

They were prepared- buildings were built to withstand earthquakes

Responses
Anti disaster drills are now being practiced

Field hospitals

10 days later 90% of homes had power again

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2
Q

CASE STUDY- Rift valley

A

East Africa Rift Valley

A continental rift valley forms where a constructive plate margin is within a continent. The continent is pulled apart by convection currents in the mantle. This causes blocks of earth to drop, forming rift valleys with steep sides

5500km

Formed by the arabian plate and 2 parts of the African plate

National parks and tourism

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3
Q

CASE STUDY- Fold mountain and how it is used by people

A

The Andes

West coast of South America

Formed by the Nazca and South American plate

Volcanoes and earthquakes occur there

Farming- Good quality soil

mining- Contains lots of silver and gold

hydroelectric power- Steep slopes and narrow valleys means it is ideal

tourism- Many natural attractions- volcanoes, glaciers ect

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4
Q

What are active volcanoes?

A

Volcanoes that have recently erupted

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5
Q

What are dormant volcanoes?

A

Volcanoes that have not erupted in a longtime

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6
Q

What are extinct volcanoes?

A

Volcanoes around which there has been no record of tectonic activity

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7
Q

Describe a shield volcano

A

Constructive plate margins - above hot spots

Plates move apart, magma pushes to the earths surface.

Runny lava- flows long distances before solidifying so flows considerable distances from crater

Eruptions are gentle oozings of lava

EG Mauna Loa, Hawaii

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8
Q

Describe a composite volcano

A

Destructive plate margin

Thick, acidic lava- cools quickly creating a cone shape with steep sides

Eruptions of ash, lava

EG MT VESUVIUS - Italy

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9
Q

What are Lahars?

A

Mudflows - ash and water travel at great speeds

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10
Q

What is a pyroclastic flow?

A

Burning clouds of ash and gas

High temperatures

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11
Q

Where is the focus of an earthquake?

A

The source of the shock wave

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12
Q

Where is the epicentre of an earthquake?

A

The point on the earths surface directly above the focus

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13
Q

What is the size of an earthquake measured with?

A

A seismograph along the richer scale

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14
Q

CASE STUDY- TSUNAMI

A

Boxing Day tsunami- 2004

earthquake in the Indian Ocean

Giant waves crashed into 30 countries- Indonesia was worst affected

250,000 people died

Aid was given by international countries

Warning system has now been set up

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15
Q

How can you prepare for an earthquake?

A

Educate- training programs or educate by TVs or radio

Preparation- put together emergency kits

Building- earthquake proof buildings in major cities- designed to absorb the energy of an earthquake and to withstand the movement of the earth. Roads and bridges can also be designed to withstand the power of earthquakes

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16
Q

How can you predict an earthquake?

A

Laser beams can be used to detect plate movement

Seismometer is used to pick up vibrations in the earths crust

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17
Q

How can you predict a volcanic eruption?

A

Sensors- measure levels of sulfur dioxide and carbon dioxide gas

Tilt metres- monitor changes in the shape of a volcano that occur as it fills with magma

Ultrasound- detect movements in magma

Satellites- monitor the temperature and shape of volcanoes

Seismometers- detects vibrations in the earth’s crust

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18
Q

How can you prepare for a volcanic eruption?

A

Hazard maps- are drawn to show areas at risk

Evacuation

emergency supplies are ready

Emergency services are trained

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19
Q

CASE STUDY-volcanic eruption in an LEDC

A

Merapi Volcano, Indonesia

  • destructive margin
  • Over 60 deaths
  • Ash collapsed houses
  • Eruption was sudden and violent
20
Q

CASE STUDY- volcanic eruption in an MEDC

A

MT St. Helens -USA

  • West coast of America
  • Destructive margin
  • 61 deaths- most due to poisonous gas
  • All fish dead
  • Roads flooded by flood water
  • Bridges broken - bad communications
  • Nothing survived within the blast zone
21
Q

Which type of crust is thinner

A

Oceanic crust

5-10 km

22
Q

Case study: how do people use an area of fold mountains?

A

The Andes

Farming- terraces creates flat land

Mining- rich mix of minerals- gold

Hydroelectric power- steep slopes and narrow valleys - ideal - melting Snow in summer increases water

Tourism- natural attractions bring tourists to the Andes creating jobs

23
Q

Describe an ocean trench

A

Deep water area which runs along the coastline which has a destructive plate margin

Created by subduction

Mark the point where oceanic crust is being pushed under continental crust

24
Q

Describe fold mountains

A

Collision plate margin
Rocks start to crumple forming folds which have different layers in

Eg Alps, Andes

25
Q

What are primary hazards of a volcanic eruption?

A

Volcanic gases

Pyroclastic flow- hot rocks, lava, ash

Ash fall

Lava flows

26
Q

What are secondary hazards after a volcanic eruption?

A

Lahars

Tsunami

27
Q

What are primary effects of an earthquake?

A

Ground shaking- buildings and bridges collapse

28
Q

What are secondary effects of an earthquake?

A

Fire

Tsunami

Landslides

Disease and famine

29
Q

CASE STUDY- Earthquake, LEDC

A

Haiti - Caribbean

2010

Destructive plate margin - on a fault zone

Main port and roads were badly damaged- meant aid was slow

220,000 people killed

8 hospitals collapsed

100,000 homes destroyed

They were not prepared- weak government and little money, never had an earthquake before

Responses-
USA sent ships,
$100 million in aid,
Field hospitals set up,

30
Q

Destructive plate margin

A

Heavier oceanic plate moves under oceanic plate (subducted) due to convection currents in the mantle.

They rub together causing earthquakes

Friction and heat from the mantle melts the rock

magma rises through cracks in the crust causing a volcanic eruption

Features- earthquakes, volcanoes, ocean trench

Examples- Nazca and South American plate

31
Q

Constructive margin

A

When two plate move away from each other, magma rises from beneath the ground

magma pushes to earths surface

Magma cools. Forming a new continental crust if the margin is within a continent or forms mountain rages beneath the sea or an island if the margin is in an ocean.

Lave can erupt

Features- Earthquake, ocean trench, mid-ocean ridges, shield volcanoes

Example- Hawaii, Mid Atlantic Ridge
Forms rift valleys if boundary is in land
Causes earthquakes and volcanos

EG MID ATLANTIC RIDGE

32
Q

Conservative margin

A

Two plates slide along side each other

They stick together causing huge amounts of pressure to build up

Pressure then release- violent earthquake

Feature- Earthquakes

Example- San Andreas Fault

33
Q

Collision margin

A

2 plates move towards each other

The plates crash into each other

Pressure causes the rocks to bend and fold

And so they are pushed upwards to form mountains

Causes earthquakes and fold mountains

Movement also causes earthquakes

Features- Earthquakes, fold mountains

Example- Alps

34
Q

How does a tsunami occur?

A

Plates shift (earthquake) displacing water above epicentre. As wave reaches shallower water, the wavelength reduces so wave night increase.

35
Q

What is the structure of the earth?

A

Crust- made of oceanic and continental plates

Mantle- convection currents from radioactive decay drive movements of plates above- semi molten rock

Core- solid due to pressure from above, solid iron and nickel

36
Q

Describe continental crust

A

Carries land

made mostly of granite-low density, igneous rock

30-50km thick

less dense

37
Q

Describe oceanic crust

A

Carries water

made mostly of basalt-high density, igneous rock

6-8 km thick

more dense

38
Q

Describe convection currents in the mantle

A

Radioactive decay in the core causes heat to rise and fall in the mantle, which creates convection currents.

These currents move the plates

Where convection currents diverge near the earth’s crust, plates move apart

Where they converge, the plates move towards each other

39
Q

What is a plate boundary?

A

The point at which 2 plates meet

40
Q

Where do volcanoes occur?

A

Where weaknesses in the earth crust allow magma and gas to erupt

41
Q

Why are people living in LEDCs at a greater risk from volcanoes?

A

because they often live in risky locations, do not have insurance, communications are poor, and so warning and evacuation may not happen

42
Q

What is an earthquake?

A

An earthquake is the result of vibrations in the earth’s crust

They are caused by shock waves travelling outwards from a sudden movement deep within the crust

42
Q

What will the impact of an earthquake depend on?

A

strength of the earthquake and distance from the epicentre

Nature of the surface rock- some rocks ‘shake’ more than others

Number of people who live in an area and time of day

Extent of preparation in the area and availability of emergency services

43
Q

Describe how tsunamis are formed

A
  • formed when energy from an earthquake vertically jolts the sea bed by several meters displacing large amount of water
  • Large wave begins to move through ocean, away from the earthquake’s epicentre
  • in deep water, the tsunami moves at great speeds. When it reaches shallow water, near the coast, the tsunami slows but increases in height
  • Some coastal areas are given not warning. The only sign is when the waterline retreats exposing the seabed and metres of beach

The tsunami comes in waves which can be several metres high

44
Q

Describe how an ocean ridge is formed

A

constructive boundary- plates move apart

magma pushes to the earth’s surface- forms new crust

which forms a ridge either side of the plate margin

eg- Mid-Atlantic Ridge

45
Q

Explain how impacts of earthquakes on people’s lives may be reduced

A

By predicting earthquakes:

  • laser beams are used to detect plate movement
  • Seismometers are used to pick up vibrations
  • Levels of radon gas are measured

By preparing for earthquakes:

  • Earthquake drills and education will mean people know what to do in an event of an eruption
  • Emergency supplies of basic items need to be stored
  • Buildings roads and bridges can all be designed to withstand an earthquake. -eg Chile earthquake, 2010 - building were earthquake proof so did not fall over, killing people

Geography (9 decks)

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