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Geography > Natural Hazards > Flashcards

Natural Hazards Flashcards

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1
Q

How does wealth affect people’s perception of hazards?

A

Richer people may be able to afford to move to areas less prone, or build homes to withstand, their perceived risk is smaller.

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2
Q

How does religion affect how people view hazards?

A

Some believe hazards are acts of God, sent to punish people.

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3
Q

How does education affect perceived risk?

A

More education means better understanding of risks, and the ability to reduce risks or mitigate impacts.

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4
Q

How can past experience affect how people see natural hazards?

A

Those who live in hazard-prone areas may have experienced hazards before, may affect perceived risks from future hazards.

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5
Q

How can personality affect perception of hazards?

A

Some people fear hazards, while some find them exciting.

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6
Q

Describe the inner core.

A

Solid ball of iron and nickel, around 6000 Degrees Celsius

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7
Q

Describe the composition of the outer core.

A

Semi-molten iron and nickel

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8
Q

What is the mantle composed of?

A

Silicate rocks, heat from radioactive decay of elements, temperature ranges between 1000-3500 Degrees Celsius, convection currents originate here.

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9
Q

What is the crust?

A

Outer layer of Earth, contains thicker(30-70km) but less dense continental crust and thinner(6-10km) but more dense oceanic. Lithosphere made up of outer mantle and crust.

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10
Q

What landforms are present at a constructive plate margin?

A

Ocean ridge formed by diverging plates underwater

Rift valleys formed by divergence beneath land

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11
Q

What is a constructive plate margin and which hazards form at these boundaries?

A

Two plates moving apart(diverging)

Volcanoes and earthquakes

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12
Q

Give an example of an ocean ridge.

A

Mid Atlantic Ridge, involves Eurasian plate and North American plate moving apart.

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13
Q

Give an example of a rift valley.

A

East African Rift System from Mozambique to the Red Sea, 4000km. Nubian and Somalian plates diverging.

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14
Q

What is a destructive plate margin and what hazards are found at these boundaries?

A

Two plates moving towards each other(converging)

Volcanoes,earthquakes, deep sea trench and fold mountains

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15
Q

What occurs when an oceanic and continental plate collide? Give an example.

A

More dense oceanic plate subducted, forming deep sea trench. Peru-Chile trench in Pacific Ocean.

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16
Q

What occurs when two oceanic plates converge? Give an example.

A

Denser of the two subducted, deep sea trench. Volcanic eruptions create island arcs, for example the Mariana Islands.

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17
Q

What occurs when two continental plates collide? Give an example.

A

Earthquakes and fold mountains form, for example the Himalayas.

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18
Q

What happens at a constructive plate margin? Give an example.

A

Two plates moving past each other, pressure builds up forming earthquakes.
Pacific plate moving past North American plate, San Andreas fault in California

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19
Q

What are magma plumes? Give an example.

A

Volcanic activity away from plate margins that can form a chain of volcanic islands, for example Hawaii.

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20
Q

Describe how magma plumes from volcanic islands.

A

Magma plume remains stationary while crust above moves. Volcanic activity in original part of crust decreases as it moves away. New volcanoes form in crust now above magma plume.

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21
Q

What are pyroclastic flows? Give an example.

A

Mixture of super heated gas, ash and volcanic rock that flows down the side of a volcano. Speeds around 80km/h and can travel as far as 15km. Travel fast and happen with little warning.
Vesuvius buried Pompeii and Herculaneum in 79 AD.

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22
Q

What are lava flows?

A

Flows from volcanic vent, speed and distance depend on viscosity, temperature and steepness of slope. Low viscosity means flows up to 10km/h and distances over 10km. Normally slow moving so people have time to evacuate.

23
Q

What are volcanic gases?

A

Lava contains CO2 and SO2 which are harmful, for example SO2 can cause breathing problems?

24
Q

What is tephra and ash fallout?

A

Material ejected from volcano that falls back down to ground and can travel thousands of kilometres. Heavier particles deposited nearer volcano, while smaller particles further away.

25
Q

Describe mudflows/lahars.

A

Volcanic material that mixes with water, 80km/h travel over 10km

26
Q

Describe acid rain

A

Volcanic gases can react with water vapour in atmosphere. SO2 and H2O form sulfuric acid.

27
Q

What is the volcanic activity like at constructive plate margins?

A

Basaltic lava, hit and low viscosity, flowing easily and quickly. Eruptions frequent and violent but do not last.

28
Q

What is the volcanic activity like at destructive margins?

A

Andesitic and rhyolitic lava, cooler and more viscous, flows less quickly and eruptions are intermittent and short lived. Viscous lava forms blockages in volcanic vents, pressure builds up resulting in more violent eruptions.

29
Q

What is the volcanic activity like at hot spots above magma plumes?

A

Basaltic lava, volcanoes with gentle slopes: shield volcanoes.

30
Q

What is the focus?

A

Shockwaves spread out from the focus, seismic waves stronger and cause more damage here.

31
Q

What is the epicentre?

A

Point on Earth’s surface where volcano felt first, directly above focus.

32
Q

How do tsunamis form?

A

Large waves caused by displacement of large volumes of water. Earthquakes cause seabed to move, displaces water, waves radiate out from epicentre.

33
Q

What conditions lead to a very powerful tsunami?

A

Formation closer to coast, deep water

34
Q

What is soil liquefaction?

A

Soil saturated, vibrations cause it to act like a liquid. Soil therefore weaker and easier to deform, more likely to subside with a heavy weight on top.

35
Q

Where do the biggest earthquakes form?

A

Destructive margins, subduction zone causes massive pressure to build up.

36
Q

Where do lower magnitude earthquakes form?

A

Constructive margins

37
Q

How does the depth of focus affect earthquake magnitude?

A

Deep focus leads to high magnitude earthquakes, generally do less damage because shockwaves have to travel further to reach surface which reduces their power.

38
Q

Describe a ground fire.

A

Where the ground itself burns, usually peat and tree roots. Slow, smouldering fire with no flame, and little smoke.

39
Q

Describe a surface fire

A

Leaf litter and low-lying vegetation burn, can be low or high intensity

40
Q

Describe a crown fire

A

Fire moves rapidly through canopy, intense and fast-moving

41
Q

How does vegetation type affect intensity of wildfires?

A

Thick undergrowth and closely spaced trees allow fire to travel easily. Eucalyptus and pine contain a lot of oil and burn easily, and eucalyptus also sheds strips of bark which can help the fire spread easily and quickly.

42
Q

How do fuel characteristics affect intensity of wildfires?

A

Fine, dry material, for example long grass and thin twigs, catch fire and burn most easily. Large amounts of fuel that form continuous cover help fire spread and burn longer

43
Q

How does climate and recent weather affect intensity of wildfires?

A

Rainfall must be sufficient for vegetation to grow and act as fuel. Distinct dry season allows water in vegetation to dry up so its more flammable. Strong oxygen provides winds to help fire spread burning embers.

44
Q

How does fire behaviour affect intensity of wildfires?

A

A creeping fire moves across ground surface slowly, whereas a running fire spreads rapidly and is more intense, fires can throw burning debris that help it spread.

45
Q

Where do storm hazards develop?

A

Over warm water, as moist air rises and condenses it releases energy increasing wind speed?

46
Q

What disturbance near the sea surface is needed?

A

An area of low pressure

47
Q

What temperature should the sea water be?

A

Above 27 Degrees Celsius to a depth of 50m. This ensures lots of water evaporates.

48
Q

What should happen to the air?

A

Convergence of air in lower atmosphere, either within ITCZ or along boundary between warm and cold air masses, forces warm air to rise.

49
Q

In which location do storm hazards from?

A

At least 5 degrees from the equator, where the Coriolis effect is strong enough to create spin. Therefore, they form in the tropics and initially move north west due to strong easterly winds.

50
Q

How are storm hazards classified?

A

Caribbean Sea= Hurricanes
Bay of Bengal= Cyclones
China Sea= Typhoons

51
Q

Describe the composition of storm hazards?

A

Centre of storm, area of very low pressure is called the eye.
Rising air spirals in eyewall creating strong winds.
Near top of storm, outflow of moisture-laden air, cloud cover extends for a large distance.

52
Q

How is the intensity of storm hazards measures?

A

Using the Saffir-Simpson Scale which is based on wind speed. Category 5= Over 250km/h. Category 1= 120-150km/h

53
Q

How do storm surges come about?

A

A rise in sea level is caused by high winds and low pressure.

54
Q

Why is heavy rain a characteristic of storm hazards?

A

Warm, moist air cools and condenses. In 1966, 1000mm of rain fell in 12 hours at La Réunion during Storm Denise

Geography (26 decks)

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