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Geography > Volcanoes and Earthquakes > Flashcards

Volcanoes and Earthquakes Flashcards

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1
Q

Where are volcanoes and earthquakes usually found?

A

Volcanoes and earthquakes tend to occur in similar places, along narrow belts, which follow the lines of the plate boundaries.

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2
Q

What is the “Ring of Fire”?

A

The Ring of Fire is a concentration of tectonic activity around the Pacific Ocean.

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3
Q

What direction do constructive margins move?

A

Away from each other.

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4
Q

What happens to constructive plate margins? (the steps)

A
  • plates move apart due to convection currents
  • magma rises up though the gap between the two plates because magma is light enough to do so
  • the magma cools down and turns into solid rock creating new land
  • a volcano is formed - causes gentle volcanic eruptions
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5
Q

Give an example of a volcano created by constructive plate margins:

A

Iceland, on the Mid-Atlantic Ridge.

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6
Q

What direction do destructive margins move?

A

The oceanic crust subducts the continental crust.

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7
Q

What happens to destructive plate margins? (the steps)

A
  • the oceanic and continental plates move towards each other due to convection currents
  • the oceanic crust then subducts the continental crust because it is more dense and is therefore heavier
  • the oceanic crust melts into magma due to the friction and the heat of the subduction zone and this rises up through the continental crust forming volcanoes
  • the continental crust crumples up into layers of mountains
  • the volcanic eruptions are violent
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8
Q

Give an example of a volcano created by destructive plate margins:

A

Pacific Ring of Fire

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9
Q

What direction do collision margins move?

A

The two continental plates move towards each other.

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10
Q

What happens to collision plate margins? (the steps)

A
  • two continental plates move towards each other due to convection currents
  • they then collide with each other
  • the layers of continental crust (rock) crumple up and fold into layers of mountains because there is no oceanic crust to subduct the continental crust
  • this causes violent earthquakes
  • there is no volcanic activity due to no oceanic crust being melted
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11
Q

Give an example of a mountain created by collision plate margins:

A

The Himalaya mountains which is the North of India

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12
Q

What direction do conservative margins move?

A

The two plates slide past each other

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13
Q

What happens to conservative plate margins? (the steps)

A
  • pressure and stress build up along the boundary between two plates
  • the two plates then slide past each other due to convection currents
  • this then causes violent earthquakes
  • there is no volcanic activity due to no oceanic crust being melted
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14
Q

Give an example of a fault created by conservative plate margins:

A

The San Andreas Fault which is on the west coast of North America.

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15
Q

What are compressional/convergent plates?

A

These are plates moving towards each other (destructive or collision)

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16
Q

What are tentional/divergent plates?

A

These are plates moving away from each other (destructive)

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17
Q

What is magma?

A

Magma is molten rock stored underground.

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18
Q

What is a magma chamber?

A

A magma chamber is an underground store for magma.

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19
Q

What is a main vent?

A

A main vent is the main channel for magma to travel to the surface.

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20
Q

What is a crater?

A

A crater is the opening at the top of a volcano.

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21
Q

What is a lava flow?

A

A lava flow is molten rock flowing down the side of a volcano.

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22
Q

What are volcanic bombs?

A

Volcanic bombs are lumps of molten rock thrown out of the volcano.

23
Q

What is steam, ash and dust?

A

Steam, ash and dust are hot clouds of small particles.

24
Q

What is a secondary vent?

A

A secondary vent is a channel which forms when the main vent becomes blocked.

25
Q

What are ocean trenches?

A

Ocean trenches are dips in the ocean. They are usually very deep as they are between 5000-10000 metres.

26
Q

Where are ocean trenches mainly located?

A

Ocean trenches are mainly located along the Pacific Ocean.

27
Q

How are ocean trenches formed?

A

When a dense ocean plate (oceanic) collides with another ocean plate or a continental plate, the denser plate “subducts”, or sinks back into the mantle, this therefore created a dip which is an ocean trench.

28
Q

What are 5 benefits of living near a volcano?

A
  • good fertile soil - to grow crops
  • big mines - to extract minerals and create jobs
  • geothermal activity - hot water for leisure centres
  • power stations - powered by the Earth’s natural activity
  • beautiful views - attracts tourists
29
Q

What are 3 dangers of living near a volcano?

A
  • the water around the volcano tends to be contaminated - diseases such as chlorera
  • volcanic bombs - contribute to the green house effect
  • pyroclastic flows - destroy everything in their way
30
Q

What are the characteristic features of a shield volcano?

A
  • cone with a wide base and gentle slopes
  • made of lava only
  • regular and frequent eruptions
  • lava pours out with little violence
31
Q

What is the formation of a shield volcano?

A

As the two plates move apart, magma rises up through the mantle. This then adds new rock to the spreading plates. Occasionally some of the magma is forced up to the surface through a vent.

32
Q

Give 2 examples of shield volcanoes:

A
  • Hekla and Surtsey in Iceland

- Mauna Loa and Kilavea in Hawaii

33
Q

What are the characteristic features of a composite cone volcano?

A
  • tall cone with a narrow base and steep sides
  • made of alternate layers of lava and ash
  • irregular eruptions with long dormant periods
  • violent explosions are possible
34
Q

What is the formation of a composite cone volcano?

A

When the plates collide, the oceanic plate subducts under the continental plate. The plate is then melted and destroyed in the subductional zone. In the subduction zone, the plate forms a pool of magma. The heat and pressure then forces the magma along a crack where it erupts t the surface to build up a volcano.

35
Q

Give 2 examples of composite cone volcanoes:

A
  • Etna, Vesuvious and Stomboli in Italy

- Krakatoa in Indonesea

36
Q

What are 4 methods/techniques that are used to monitor earthquakes?

A
  • satelittes - that pick up signals
  • scientists - monitoring volcanoes, sampling magma
  • seismicity - measured using seismometres
  • hydrology
37
Q

What is a Richter scale similar to?

A

A Richter scale is similar to a VEI.

38
Q

What is a seismometer?

A

A seismometer is an instrument used to measure earthquakes.

39
Q

What is a seismograph?

A

A seismograph is the reading that the seismometer creates.

40
Q

What are seismic waves?

A

Seismic waves are energy which is released from the earthquake.

41
Q

What are seismologists?

A

They are geographer/scientists who measure and study earthquakes.

42
Q

What is the epicentre?

A

The epicentre is directly above the focus on the surface of the Earth.

43
Q

What is the focus?

A

The focus is the origin of the earthquake.

44
Q

What is a mercalli scle?

A

A mercalli scale is the intensity of the earthquake.

45
Q

What are 3 examples of primary effects?

A
  • collapsing buildings
  • people being killed by being trapped
  • collapsing roads and bridges
46
Q

What are 3 examples of secondary effects?

A
  • disease - from dirty water
  • landslides
  • tsunamis
47
Q

What are 3 examples of immediate responses?

A
  • safety
  • evacuation
  • emergency services
48
Q

What are 5 examples of medium term responses?

A
  • retrieving normality
  • jobs
  • development
  • rebuilding
  • replacing
49
Q

What are 3 examples of long-term responses?

A
  • planning
  • predicting
  • building earthquake proof buildings
50
Q

What are the 3 P’s?

A
  • prediction
  • protection
  • preparation
51
Q

What is prediction?

A

Attempts to forecast an event - where and when it will happen.

52
Q

What is protection?

A

Constructing buildings so that they are safe to live in and will not collapse.

53
Q

What is preparation?

A

Organising activities and drills so that people know what to do in the event of an earthquake.

Geography (24 decks)

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