Hazards

Question 1

Explain how fossil records can be used as evidence of continental drift and plate tectonics theory (4)

Answer 1

• Fossils are the preserved traces of animals and plants found inside rock, they help date geological material
• The geographic distribution of fossils has helped to understand the spread of different species over time.
• Anomalies in the distribution presented a problem for geologists as very similar fossils were discovered in rock masses separated by vast distances or oceans.
• Similar fossilised remains of plants and animals found on different continents provided evidence for Wegner of continental drift

Question 2

Environmental impacts of tectonic hazards are more significant than economic impacts.’
How far do you agree with this statement? (20)

Answer 2

• Liquefaction was a very significant environmental impact i Liquefaction occurs when loosely packed water logged sediments at or near the ground lose their strength in response to ground shaking. CC in 2011 saw the city centre subside VS this led to a greater economic cost. $40bn spent on redesigning and rebuilding.
• Eruption of Nyiragongo melted mains water pipes and damaged a huge 5000m3 reservoir. 3629 houses were ravaged by lava, 23 roofs of houses were blown away VS This meant people could not work, so incomes were affected.
• Overall the economic cost is greater in MEDCs and the environmental cost is greater in LEDCs

Question 3

‘Managing hazards in MEDCs is more successful than any other area of the world.’
How far do you agree with this statement? (20)

Answer 3

• NZ were very fast with relief to Christchurch. Full emergency action plan within 2 hours. All survivors rescued within 24 hours. VS We could argue the DRC was also just as fast to evacuate. The governor instantly declared an evacuation and 400,000 residents were evacuated BUT 13 died in the evacuations, and there was not suitable camp for evacuees.
• Puerto Rico had 3000 deaths from a category 4 storm compared to only 88 dead from Hurricane Harvey also category 4. These were both within the USA a MEDC VS Puerto Rico is much more undeveloped. Double the unemployment, high poverty rates, and does not hold the same states power and funding like the 50 states.

Question 4

• Explain 2 pieces of evidence that support the theory of continental drift (4)

Answer 4

• Evidence for sea floor spreading where paleomagnetism has been used to determine the age of sea floor rocks
• Africa and S America shapes of west and east coasts seem to fit together
• Fossils from land based animals found in S America and Africa suggest the continents were once joined

Question 5

Explain how volcanic hazards are affected by types of volcanic eruption (4)

Answer 5

• Explosive volcanoes, found at destructive plate boundaries, will have pyroclastic flows and other projectiles given the pressure build up from the complex magma network and plugging of vents due to the high silica content of the magma.
• Effusive volcanoes found at constructive plate boundaries will have a lower viscosity lava which moves much faster. Means less pressure build up before eruption means little tephra and ash but gas emissions still possible

Question 6

Explain 2 scales used to assess earthquake magnitude (4)

Answer 6

• The Richter scale as no upper limit though the largest earthquakes score around 9. Uses the amplitude of seismic waves to determine EQ magnitude. Logarithmic so each increase the EQ is 10 times bigger
• Moment magnitude scale measures the energy released by an EQ. It is more accurate than the Richter scale, the amount of energy released is related to the geological properties of the rock.

Question 7

Outline the features of the Mercalli scale (4)

Answer 7

• The Mercalli scale is a qualitative scale that measures the intensity of EQs
• The scale quantifies the impacts of an EQ that can be felt and seen
• The intensity is normally highest near the epicentre. It assesses EQs with 12 degrees of intensity
• Especially useful in targeting responses in LEDCs

Question 8

Explain how movements of the Earth’s crust form rift valleys (4)

Answer 8

• Rift valleys form on constructive plate margins. Convection currents at this plate margin diverge, pulling the plates apart.
• The crust has stretched and become thinner. The stresses that this creates results in faulting parallel to the plate boundary. Allowing sections of crust to sink into the mantle as they are no longer supported by the structure of the tectonic plate.

Question 9

‘‘Environmental impacts of volcanic activity are the most
damaging.’
How far do you agree with this statement? (9)

Answer 9

• Eruption can destroy built environment. Mt Nyiragongo melted water pipes and damaged a 5000m3 reservoir. This led to further secondary impacts such as droughts and worse water quality VS economic is worse. Markets and banks were destroyed meaning the informal sector was damaged
• We could argue social were worse. 32 people killed in eruption. 400000 people evacuated. 13 killed during the evacuations
• Overall disagree, as social was worst, followed by environmental

Question 10

• To what extent do other physical factors contribute to hazards caused by volcanic eruptions? (20)

Answer 10

• Ash is a volcanic material. Generally erupted during explosive reactions on destructive boundaries. BUT We also have wind which causes the extent of the ash fallout
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