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Geography > The Restless Earth > Flashcards

The Restless Earth Flashcards

1
Q

What is a plate?

A

A section of the earth’s crust.

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2
Q

What is a plate margin?

A

The boundary where two plates meet.

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3
Q

What is the mantle?

A

The dense mostly solid layer between the outer core and crust.

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4
Q

What is a convection current?

A

The circular currents of heat in the mantle.

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5
Q

Describe the structure of the earth? (in to out)

A

Inner core,outer core, mantle, crust.

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6
Q

What is oceanic crust?

A

Crust beneath the oceans. It is:

  • newer (mostly less than 200 million years old)
  • Denser
  • Can sink
  • Can be renewed and destroyed
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7
Q

What is continental crust?

A

It is crust beneath the continents. It is:

  • Older
  • Less dense
  • Cannot sink
  • Cannot be renewed or destroyed
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8
Q

What is a subduction plate margin?

A

It is when an oceanic plate sinks under a continental plate.

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9
Q

What is a collision plate margin?

A

When two continental plates move towards each other.

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10
Q

What is a constructive plate margin?

A

It is when two plates move away from each other.

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11
Q

What is a conservative plate margin?

A

It is when two plates slide along next to each other.

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12
Q

Describe what happens at a destructive plate margin with an oceanic and continental crust?

A

Convection currents in the mantle cause plates to move together. The denser oceanic crust sinks under the lighter continental in a process called subduction. Great pressure is exerted and the oceanic plate is destroyed as it melts to form magma.

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13
Q

Describe what happens at a destructive plate margin between two continental plates?

A

When two continental plates meet each other because of the convection currents in the mantle, they collide rather than one sinking. This collision boundary is a different type of destructive boundary instead of a subduction zone.

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14
Q

What determines the movement of the plates?

A

The direction of the convection current determines the movement of the tectonic plates.

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15
Q

Example of a subduction plate margin?

A

Philippines with Pacific

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16
Q

Example of a collision plate margin?

A

African and Eurasian

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17
Q

Example of a constructive plate margin?

A

Pacific with Nazca

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18
Q

Example of a conservative plate margin?

A

Jan de Fuca with North American

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19
Q

What is a divergent plate margin?

A

This is where plates move apart.

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20
Q

What is a convergent plate margin?

A

This is where plates collide.

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21
Q

What is a transform plate margin?

A

This is where plates slide horizontally past one another.

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22
Q

What did Alfred Wegner suggest happened to the plates in his theory of continental drift?

A

He suggested that all the continents had originally been joined together as one land mass, after which they had separated and slowly drifted along the oceans floor to their current locations.

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23
Q

What evidence supported Alfre Wegner’s theory?

A
  • The apparent fit of the coastlines of South America and Africa.
  • Similar rock types where found in two continents ( Argentina in South America and South Africa in Africa)
  • Similar fossils were found on either side of the Atlantic Ocean.
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24
Q

Why do you think his theory was generally not accepted?

A

Lack of evidence to show how the continents moved.

25
Q

How was the theory of continental drift developed and refined to become the theory of tectonics?

A

It became clear that new oceans crusts were continually being created in zones in the middle of the oceans. Sea floor spreading was used to modify his original ideas. The continents were moving but the creation of crust along-mid ocean ridges was the driving force.

26
Q

How are fold mountains formed at a converging plate margin? (Between two continental plates)

A

The plates push layers of accumulated sediment in the sea in geosynclines together and eventually upwards.
Overtime, a fold mountain range is created.

27
Q

How are fold mountains formed at a converging plate margin? (Subduction Zone)

A

As the oceanic plate subducts underneath the continental plate, the pressure and friction causes wrinkles to form. Overtime these wrinkles on the earth’s crust above the continental plate become fold mountains.

28
Q

What is a composite volcano?

A

A steep sided volcano that is made up of a variety of materials, such as lava and ash.

29
Q

What is the crust?

A

The outer layer of the earth.

30
Q

What is a shield volcano?

A

A broad volcano that is mostly made up of lava.

31
Q

Where do composite volcanoes form?

A

Destructive plate margins

32
Q

Where do shield volcanoes form?

A

Constructive plate boundaries.

33
Q

What are characteristics of composite volcanoes?

A
  • They are made up of alternating layers of lava and ash.
  • The eruptions from these may be pyroclastic flow (mixture of hot steam, ash, rock and dust).
  • Steep sided with distinctive core shape.
  • High with narrow base
  • rare but violent eruptions.
34
Q

What are the characteristics of shield volcanoes?

A
  • Have Gentle slopes with a wide base
  • Runny lava
  • Frequent but non violent eruptions
35
Q

Formation of a composite volcano?

A

Plates move towards each other, at a destructive plate margin due to convection currents. The denser oceanic plate sinks beneath the continental plate. Melting of the oceanic plate occurs in the subduction zone due to friction and heat which creates a pool of magma. This rises and the pressure is released in an explosive eruption often along a fault. Giving a steep sided volcano of lava and ash.

36
Q

Ways to monitor and predict volcanoes?

A
  • Robots called ‘Spiders’ can monitor the change in gases produced.
  • Earthquakes are a sign of an eruption.
  • Tilt-meters can identify the change in the height of the slope.(when a bulge appears its and indication magma is moving below)
  • Global positioning systems (GPS) use satellites to detect movement as little as 1mm.
  • Digital cameras on the rim of craters.
  • Change in temperature (Can be seen from satellites)
37
Q

What is a supervolcano?

A

A mega colossal volcano that erupts at 1,000km3 of material.

38
Q

Differences between a composite and supervolcano?

A
  • Composite volcanoes have a magma chamber whereas supervolcanoes have magma bubbles (much larger)
  • Composite Volcanoes are steep sided a have a narrow base whereas supervolcanoes have a caldera and are much larger.
39
Q

How does a supervolcano form?

A
  • Rising magma cannot escape and a large bulge appears in the surface.
  • Cracks appear in the surface and gas and ash erupt from the magma bubble.
  • The magma chamber collapses, forming a depression called a caldera.
40
Q

What is a caldera?

A

The depression of the supervolcano, marking the collapsed magma chamber.

41
Q

What are fissures?

A

They are extended openings along a line of weakness that allows magma to escape.

42
Q

What is geothermal?

A

Water that is heated beneath the ground, which comes to the surface in a variety of ways.

43
Q

What is a geyser?

A

A geothermal feature in which water erupts into the air under pressure.

44
Q

What is a hotspot?

A

A section of the earth’s crust where plumes of magma rise, weakening the crust. These are away from plate boundaries.

45
Q

What is an earthquake?

A

A sudden and brief period of intense ground shaking.

46
Q

What is the focus?

A

The point in the earth’s crust where the earthquake originates.

47
Q

What is the epicentre?

A

The point at the earth’s surface, directly above the focus.

48
Q

What is the Richter scale?

A

A logarithmic scale used for measuring, based on scientific recordings of the amount of movement.

49
Q

What are shock waves?

A

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

50
Q

What is the mercalli scale?

A

A means of earthquakes by describing and comparing the damage done,on a scale of 1 to 12

51
Q

What do transverse waves cause?

A

Side to side movement, which cause much damage.

52
Q

What do longitudinal waves cause?

A

Up and down movement.

53
Q

What is the difference between a 1 and a 2 on the Richter scale?

A

X10

54
Q

What is a tsunami?

A

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

55
Q

What is a tsunami caused by?

A

A tsunami is normally triggered by an earthquake.

56
Q

What are the three p’s?

A

The collective term for prediction, protection and preparation.

57
Q

What is prediction?

A

Attempts to forecast an event - where and when it will happen - based on current knowledge.

58
Q

What is protection?

A

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

59
Q

What is preparation?

A

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

Geography (10 decks)

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