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Geography Year 9 > Earthquakes And Volcanoes > Flashcards

Earthquakes And Volcanoes Flashcards

1
Q

Why do earthquakes and volcanoes usually occur along plate boundaries?

A

The Earth’s crust is divided into plates, and at their edges, they can collide, pull apart, or slide past each other. These interactions create intense geological activity, leading to earthquakes and volcanic eruptions.

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2
Q

Oceanic crust

A

plate that is made up of more dense rock. It sinks easily due to its density and is constantly created at boundaries. It is ‘young/new rock’ and forms our ocean bed

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3
Q

Subduction
zone

A

where one plate is forced downwards below another plate and grinds past it causing huge amounts of friction and heat. Composite volcanoes are made here

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4
Q

Continental
crust

A

this is a plate that is made up of less dense rock. Because it is less dense it doesn’t sink. It is very old and makes up our land
surfaces

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5
Q

Plate
boundary

A

where two tectonic plates meet on the earth’s surface. Earthquakes and volcanoes happen here

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6
Q

Fold mountains

A

are large mountain ranges formed by the collision and ‘folding’ of two plates as they plates continually push into one another. These can happen at convergent/destructive and collision boundaries

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7
Q

Ocean trench

A

a particularly deep point of the ocean bed where the oceanic and continental crust have dragged each other downwards

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8
Q

Composite volcano

A

a very steep volcano that is formed at a destructive boundary. The magma under the surface has high silica and is very explosive – these are the most dangerous volcanoes

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9
Q

What is the ring of fire?

A

A tectonic belt of volcanoes and earthquakes along the edges of the Pacific plate

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10
Q

What is a convergent/destructive plate boundary?

A

Usually involves an oceanic plate and a continental plate. The more dense oceanic plate is forced beneath the less dense oceanic plate as they collide. This movement can cause earthquakes and volcanoes.

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11
Q

What is a divergent/constructive plate boundary?

A

Where plates move apart from one another. When this happens the magma from the mantle rises up to make new crust. The movement of the plates over the mantle can cause earthquakes. Rising magma can also create
shield volcanoes.

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12
Q

What is a conservative/transform plate boundary?

A

At a conservative plate boundary, the plates slide past each other in opposite directions, or in the same direction but at different speeds. As the plates try to move, friction occurs and plates become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released, it sends out huge amounts of energy causing an earthquake.

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13
Q

What is a collision plate boundary?

A

When two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains. This is called a collision boundary. Earthquakes can occur at collision boundaries.

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14
Q

What are some features produced from convergent/destructive plate boundaries?

A

composite volcanoes, fold mountains and island arcs

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15
Q

What are some features produced from divergent/constructive plate boundaries?

A

mid ocean ridges, underwater volcanoes and earthquakes

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16
Q

What are some features produced from conservative/transform plate boundaries?

A

earthquakes

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17
Q

What are some features produced from collision plate boundaries?

A

fold mountains

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18
Q

What is a composite volcano?

A

cone-shaped volcano built from several layers of lava that cooled down

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19
Q

How are composite volcanoes formed?

A

-millions of years ago, magma forced its way through a weak spot in the earths surface

-the lava cooled and turned into rock. Many years later magma forced its way up again

-the process repeats creating multiple layers of rock. In between the volcano spewed out ash and steam. The ash settled on the volcano and cemented into rock

-Over millions of years the layers built up to form a volcano

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20
Q

Ocean trench

A

A particular deep point of the ocean bed where oceanic crust has been dragged down by the continental crust

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21
Q

What is seismic activity?

A

The frequency, type, and size of earthquakes experienced over a particular time

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22
Q

What happens at a convergent/destructive plate boundary?

A

-denser oceanic plate is forced below the continental plate

-less dense continental plate moves towards oceanic plate

-pressure builds up at subduction zone. friction causes melting of oceanic plate which creates gasses in the chamber

-molten rock (magma builds up in the chamber)

-when the pressure builds up magma escapes through a composite volcano

-lighter continental crust remains at the surface

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23
Q

What is an earthquake?

A

Vibrations of the earth’s crust caused by movement at plate boundaries and major fault lines

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24
Q

What is a fault line?

A

A zone of fractures between 2 blocks of rock

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25
Q

Where are fault lines found?

A

Along plate boundaries

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26
Q

What is the epicentre?

A

The point on the ground above where an earthquake happens

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27
Q

What is a focus?

A

The point along the fault in the crust where an earthquake happens

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28
Q

What are shockwaves?

A

Released from the focus. Primary waves travel forwards and backwards more quickly. Secondary waves are slower and move sideways and up and down

29
Q

What is stress and release?

A

When pressure builds between two plates stress is placed on the fault line. When the stress builds up too much it is released

30
Q

What is the Richter Scale?

A

Measures magnitude (how much the ground shakes) . It has a scale from 0-10 and is measured using a seismometer. It uses a logarithmic scale.

31
Q

What is the Mercalli Scale?

A

Measures the intensity/damage of an earthquake. It has a scale from 0-10 and is measured using observations and the resulting damage. It uses a “normal” scale.

32
Q

Primary waves

A

arrives fast and first. Moves through solid rock and fluids, pushes and pulls in the direction of travel. They move at about 8km per second and transfer energy from the focus to the epicentre.

33
Q

Secondary waves

A

slower than primary waves, only move through solid rock in an up and down motion. These move at about 4km per second and tranfer energy from the focus to the epicentre

34
Q

Love waves

A

These arrive approx. 20-30 seconds after the first 2 waves. They only travel through the surface crust and do so in a rolling motion. The ground moves side to side. Responsible for most of the shaking felt by people.

35
Q

Rayleigh wave

A

arrives at the same time as the love waves. Only travels through the surface of the crust, fastest wave, and moves up and down
like an ocean wave

36
Q

What is a hazard?

A

something that has the potential to cause harm to people, environments and economies

37
Q

How are volcanoes formed on convergent/destructive boundaries?

A

When a oceanic plate and a continental plate move towards each other, the denser oceanic plate sinks under the continental plate and melts in the mantle. This releases gaseses that make their way up to the crust and erupt through the surface.

38
Q

How are volcanoes formed on divergent/constructive boundaries?

A

Two of the same plates which move apart each other. This allows magma to rise up from the mantle which fills the gaps of the plates moving away from each other creating new crust. Magma can explode through this new crust and this volcanic activity can lead to underwater volcanoes and mid ocean ridges or rift valleys on continents.

39
Q

What is a rift valley?

A

The land version of a mid ocean ridge

40
Q

What are lava flows?

A

Magma that erupts from a volcano that flows and destroys everything in its path

41
Q

What are pyroclastic flows?

A

Fast moving currents of hot rock and gas

42
Q

What is volcanic ash?

A

A blast out of the lava dome which breaks up into fragments of lava and lifts them high into the atmosphere

43
Q

What is a volcanic bomb?

A

A mass of molten rock larger than 64 mm in diameter formed when a volcano ejects viscous fragments of lava that cool down

44
Q

What are lahars?

A

A violent type of mudflow composed of a slurry of pyroclastic material, rocks, debris and water flowing off the side of a volcano

45
Q

What is magnitude?

A

The unit the Richter scale uses to measure the shaking of the earth

46
Q

What is vulnerability?

A

How susceptible you are to facing hazards

47
Q

Primary effect

A

The effect that is directly caused by the disaster

48
Q

Secondary effect

A

indirect effects causes by the primary impacts

49
Q

What is liquidation?

A

When the ground is compressed and water is squeezed to the surface

50
Q

What is magma?

A

Molten hot rock under the earth’s surface

51
Q

What is lava?

A

Molten hot rock on top of the earth’s surface

52
Q

What is a volcano?

A

Openings or cracks in the lithosphere where magma from inside the earth can escape through the surface

53
Q

What is a depression?

A

a sunken landform

54
Q

What is a caldera?

A

a large depression formed when a volcano erupts and collapses

55
Q

How is a caldera formed?

A

-a magma chamber extrudes lava onto the surface

-as magma reaches the surface, the pressure decreases

-due to the pressure decrease the gasses in the magma expands rapidly creating massive volcanic explosions

-after the eruption the emptied magma chamber of a volcano can collapse forming a large circular depression called a caldera

56
Q

What is a magma chamber?

A

A large pool of magma beneath the vent

57
Q

What is a vent in a volcano?

A

The part of a volcano where the magma rises to the earth’s surface

58
Q

What is high silica lava?

A

Lava that is thick and sticky, leading to explosive volcanic eruptions.

59
Q

What is viscous lava?

A

Lava that flows slowly, like honey

60
Q

What is a supervolcano?

A

A volcano 1000x bigger than a regular volcano that has the potential to produce an eruption with major effects on the global climate and ecosystems

61
Q

What is the asthenosphere?

A

upper part of Earth’s mantle lying beneath the lithosphere

62
Q

How do earthquakes form?

A

As plates move in different directions over long periods of time, friction causes energy to build up. It becomes so great that the energy is released, which creates a shock wave - an earthquake.

63
Q

What causes a tsunami?

A

-A sudden shift in plate movement causes water displacement at the epicentre

-Large waves move along the sea bed, away from the epicentre

64
Q

What is PPP?

A

prediction, preparation and protection

65
Q

What is prediction in PPP?

A

Predicting earthquakes by using seismometers to monitor earth tremors

66
Q

What is a seismometer?

A

An instrument that records the motion of the ground during an earthquake.

67
Q

What is preparation in PPP?

A

In earthquake-prone countries, hospitals, emergency services and residents practise for an earthquake. They have drills in all public buildings so that people know what to do in the event of an earthquake. This helps to reduce the impact and increases their chance of survival.

68
Q

What is protection in PPP?

A

Protection involves constructing buildings so that they are safe to live in and will not collapse if an earthquake occurs

Geography Year 9 (8 decks)

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