March 2024 Earth Forces Test

Question 1

Describe the Earth’s layers.

Answer 1

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)

Question 2

What were the continents 200 million years ago?

Answer 2

Pangea, a giant supercontinent that included every continent.

Question 3

What did Pangea split into?

Answer 3

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

Question 4

What is a constructive plate boundary?

Answer 4

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.

Question 5

What are destructive (convergent) plate boundaries?
volcanoes

Answer 5

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.

Question 6

What is a conservative (transform) plate boundary?

Answer 6

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.

Question 7

What makes the crust move?

Answer 7

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.

Question 8

What are the three categories of volcanoes?

Answer 8

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

Question 9

What are the world’s main volcanic areas?

Answer 9

Pacific Ring of Fire
Mid-Atlantic Ridge
African Rift Valley

Question 10

Name 5 Volcanic Islands

Answer 10

Iceland
Canaries
Indonesia
New Zealand
Japan

Question 11

What type of volcanoes form at constructive boundaries?

Answer 11

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

Question 12

What type of volcanoes form at destructive boundaries?

Answer 12

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

Question 13

What are some hazards of volcanoes?

Answer 13

Pyroclastic Flows
Lahars
Ash/Dust
Lava Bombs

Question 14

What caused the Eyjafjallajokull eruption?

Answer 14

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

Question 15

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

Answer 15

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

Question 16

What happened after the inactivity phase.

Answer 16

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.

Question 17

When were the Eyjafjallajokull eruptions declared over?

Answer 17

October

Question 18

What were the meltwater floods?

Answer 18

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.

Question 19

What were some harmful effects of the Eyjafjallajokull eruption.

Answer 19

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.

Question 20

How did the volcanic ash from ayjakkufell spread?

Answer 20

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.

Question 21

What were the dangers of the volcanic ash cloud?

Answer 21

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.

Question 22

What are some benefits from volcanoes?

Answer 22

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

Question 23

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

Answer 23

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

Question 24

Where is Eyjafjallajokull?

Answer 24

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

Question 25

How did the eruption affect the people of Iceland?

Answer 25

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.

Question 26

What is the focus?

Answer 26

A point underground where the earthquake starts.

Question 27

What is the epicentre?

Answer 27

The point above the focus on the surface.

Question 28

What are seismic waves

Answer 28

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

Question 29

What are aftershocks?

Answer 29

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

Question 30

What is the San Andreas fault?

Answer 30

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.

Question 31

What is the Big One?

Answer 31

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”.

Question 32

How does a tsunami form?

Answer 32

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.

Question 33

What is a seismometer?

Answer 33

The main instrument which detects and records shock waves

Question 34

Which shockwave comes first?

Answer 34

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

Question 35

Which shockwave comes second?

Answer 35

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).

Question 36

Which shockwave comes third?

Answer 36

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.

Question 37

What does the Richter scale measure?

Answer 37

The energy produced by an earthquake.

Question 38

How do you predict Earthquakes?

Answer 38

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.

Question 39

How do you prepare for Earthquakes?

Answer 39

Government websites giving advice.

Regular safety drills.

Strict planning laws.

Question 40

How do you protect against earthquakes?

Answer 40

Cross-bracings

Auto-shutters over glass

Shock absorbers in foundations

Question 41

How do destructive boundaries form earthquakes?

Answer 41

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.