March 2024 Earth Forces Test Flashcards

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1
Q

Describe the Earth’s layers.

A

Crust - 8-40 km. Solid and made of rock.
Mantle - 2900 km. Liquid and made of rock.
Outer Core - 2250 km. Liquid and made of metal.
Inner Core - 1300 km. Solid and made of nickel and iron (possibly gold)

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2
Q

What were the continents 200 million years ago?

A

Pangea, a giant supercontinent that included every continent.

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3
Q

What did Pangea split into?

A

Laurasia (North America and Europe)
Gondwanaland (Africa and South America)
India
Australia

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4
Q

What is a constructive plate boundary?

A

Two plates move away from each other, usually under the sea. Molten rock known as magma rises up between the gap in the plates forming volcanoes. Over time they will form new land, e.g. Iceland Mid-Atlantic Ridge.

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5
Q

What are destructive (convergent) plate boundaries?
volcanoes

A

Here, an oceanic plate and a continental plate collide. The oceanic plate is lighter and gets forced underneath the continental plate, where it starts to melt. The molten rocks rise through cracks in the crust forming volcanoes.

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6
Q

What is a conservative (transform) plate boundary?

A

When two plates are sliding past each other in opposite directions. The rough edges often get snagged together causing friction to build up. When one plate breaks free, tremendous amounts of energy can be released causing an earthquake. e.g. the San Andreas Fault.

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7
Q

What makes the crust move?

A

The heat from the earth’s core produces convection currents, causing the mantle to move. The plates move very slowly by a few centimetres each year. This process is called plate tectonics.

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8
Q

What are the three categories of volcanoes?

A

Active - is currently erupting, or has erupted during recent times - active magma chamber

Dormant - not erupted lately, but likely to - slowly filling magma chamber

Extinct - not erupted lately, and never will again - inactive magma chamber

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9
Q

What are the world’s main volcanic areas?

A

Pacific Ring of Fire
Mid-Atlantic Ridge
African Rift Valley

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10
Q

Name 5 Volcanic Islands

A

Iceland
Canaries
Indonesia
New Zealand
Japan

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11
Q

What type of volcanoes form at constructive boundaries?

A

Shield volcanoes, e.g. Mt Loa.
Eruptions are less ‘explosive’ as magma constantly escapes. Gentle slopes due to liquidy lava.

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12
Q

What type of volcanoes form at destructive boundaries?

A

Composite volcanoes e.g. Mt Rainier. Eruptions are violent as pressure builds and water subducts. Steep slopes due to sticky lava.

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13
Q

What are some hazards of volcanoes?

A

Pyroclastic Flows
Lahars
Ash/Dust
Lava Bombs

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14
Q

What caused the Eyjafjallajokull eruption?

A

Minor earthquakes started in 2009, and the volcano swelled in size. Seismologists detected this.

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15
Q

What happened initially when the volcano started activity on 20th March?

A

It was a tourist attraction and was hardly dangerous. Then it went through a two day period of inactivity on 10th April.

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16
Q

What happened after the inactivity phase.

A

The volcano showed its bite. 60,000 litres of lava punched through the glacier every second. 250 million m³ of tephra was ejected into the air from the volcano. Its activity decreased on 21st May.

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17
Q

When were the Eyjafjallajokull eruptions declared over?

A

October

18
Q

What were the meltwater floods?

A

The flat plains between the volcano and the sea were exposed to the freezing water flowing at up to 3000m3/s. This made access to the volcano difficult and destroyed bridges along roads.

19
Q

What were some harmful effects of the Eyjafjallajokull eruption.

A

313 airports across Europe were forced to close for up to 6 days.

Airlines lost £130 million per day, with a total loss of £1.75 billion and had to pay for passengers stranded in hotels.

Products such as medical drugs were unable to be transported.

20
Q

How did the volcanic ash from ayjakkufell spread?

A

When the volcano erupted into glacial ice it rapidly cooled the lava and created an fine-grained ash cloud that travelled towards mainland Europe at heights up to 30,000ft.

21
Q

What were the dangers of the volcanic ash cloud?

A

The ash damages airplanes wings, tails and windows. When sucked into a plane’s turbine the ash melts and coats the blades with a thin film of glass. The freezing air at high altitude causes this glass to shatter, destroying the engine.

22
Q

What are some benefits from volcanoes?

A

Creation of rocks - building material
Tourism - Iceland’s biggest industry. Creates jobs, more money for economy.
Fertile soil for farmers - ash puts minerals into the soil
Geothermal energy - cheaper for Iceland
Precious gems - create wealth

23
Q

Apart from the things that volcanoes directly give off, eg ash, lava, what other hazards do volcanoes cause?

A

Lahars (mudflows). The heat from eruptions can melt snow lying on the volcano, which when mixed with ash can form devastating mudslides.

Ashfalls and acid rain.

Tsunamis

24
Q

Where is Eyjafjallajokull?

A

Mid-Altlantic Ridge between the North American and European plates. Very South Iceland.

25
Q

How did the eruption affect the people of Iceland?

A

Cancelled planes in the Westman Islands, they had to use slow ferries to transport their fish.
A 3mm layer of ash was deposited across the landscape, smothering cereal crops and livestock were kept indoors.
During the eruption the area was plunged into darkness and breathing masks were recommended.

26
Q

What is the focus?

A

A point underground where the earthquake starts.

27
Q

What is the epicentre?

A

The point above the focus on the surface.

28
Q

What are seismic waves

A

They move outwards from the focus causing the crust to shake.

29
Q

What are aftershocks?

A

When after a big earthquake, the crust takes time to settle down into its new position. This often produces minor earthquakes - aftershocks.

30
Q

What is the San Andreas fault?

A

In California, the Pacific Plate slides north past the North American Plate by 6cm each year, along a crack in the crust called the San Andreas Fault.

31
Q

What is the Big One?

A

Friction along the San Andreas fault could cause the plates to jolt by 13 metres, producing a huge quake, which most Californians are expecting - the “Big One”.

32
Q

How does a tsunami form?

A

When an earthquake starts under the ocean causing a rupture on the sea bed. Water is displaced and forced upwards, creating high waves which can race at very high speed towards the land.

33
Q

What is a seismometer?

A

The main instrument which detects and records shock waves

34
Q

Which shockwave comes first?

A

Push/ Primary Waves - They move very fast but do not cause much damage.

35
Q

Which shockwave comes second?

A

Shake/Secondary Waves -Cause shaking from side to side and are responsible for much of the damage to buildings in an earthquake, but are slower (2-4km/sec).

36
Q

Which shockwave comes third?

A

Long Waves - These are the slowest, but can cause problems furthest from the epicentre. Buildings weakened by the shocks of the S waves can be flattened and destroyed by L waves.

37
Q

What does the Richter scale measure?

A

The energy produced by an earthquake.

38
Q

How do you predict Earthquakes?

A

Seismometers can be used to test for tremors in the ground

Satellite and GPS systems can detect slight movements near fault lines.

Lasers can be lined up across fault lines. When the detector cannot pick up the laser beam it may indicate the ground is starting to move.

39
Q

How do you prepare for Earthquakes?

A

Government websites giving advice.

Regular safety drills.

Strict planning laws.

40
Q

How do you protect against earthquakes?

A

Cross-bracings

Auto-shutters over glass

Shock absorbers in foundations

41
Q

How do destructive boundaries form earthquakes?

A

Where two continental plates collide, the land buckles and is forced upwards, producing ranges of fold mountains. Friction between the colliding plates can produce powerful earthquakes.