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Geography GCSE > Global Hazards > Flashcards

Global Hazards Flashcards

1
Q

Global Atmospheric Circulation

A
  1. At the equator the Sun warms the earth, transferring heat above, causing it to rise creating a low pressure belt (rising air, clouds + rain)
  2. As air rises it cools and moves out to 30° N + S of the equator
  3. At 30° N + S of equator, cool air sinks, creating a high pressure belt (low rainfall + no clouds)
  4. Cool air reaches ground and moves as trade winds either back to equator or towards poles
  5. At 60° N + S of the equator, warmer trade winds meet colder air from the poles; warmer air is less dense so it rises to cause low pressure
  6. Some air moves back towards the equator + the rest moves towards the poles
  7. Cool air sinks at the poles creating high pressure which is drawn back to equator as trade winds
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2
Q

Climate Zones

  1. Polar
  2. Temperate
  3. Tropical
A
  1. Temperatures low all year
  2. Moderate summers and winters - low pressure belt at 60° N/S caused by rising air from two cells meeting means frequent rainfall
  3. Hot temperatures and high rainfall all year - usually near equator where low pressure and high rainfall comes from the rising air from 2 cells meeting
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3
Q

Global Atmospheric Circulation leading to extreme weather - Wind

A

Winds are weak in high + low pressure belts
Winds are strong in between pressure belts
If difference in pressure between high and low pressure areas, winds can be very strong (e.g. North coast of Australia)

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4
Q

Global Atmospheric Circulation leading to extreme weather - Temperature

A

The equator recieves the most solar energy from the Sun + the poles receive the least
Warm air moves from the equator to the poles due to atmospheric circulation of heat
Temperature very high in high pressure areas (30° N/S of equator) as there are few clouds (due to sinking air) to block energy from Sun

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5
Q

Global Atmospheric Circulation leading to extreme weather - Precipitation

A

Precipitation (rain,snow etc.) occurs when warm, wet air rises and cools causing water vapour to condense
Precipitation is frequent in low pressure belts as air rises (rainforests are usually in low pressure zones)
Opposite for high pressure belts - sinking air means little precipitation

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6
Q

Australia vs UK weather - temperature

A

Average summer temp. 33°C vs 23°C
Temps over 40°C in Australia are considered very hot and temps over 30°C in England are considered very hot
Australian summers 10°C hotter than UK summers and for both, extremely high temps are about 7°C hotter than average

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7
Q

Australia vs UK weather - precipitation

A

Average annual rainfall in Australia is 465mm and in England is 1154mm
Extremely wet years in Australia results in over 550mm of rain and in England results in over 1200mm
Extremely dry years in Australia means less than 350mm but in England is less than 950mm

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8
Q

Australia vs UK weather - wind

A

Australia has stronger extreme winds than the UK does
Australia is often affected by tropical cyclones which cause strong winds
In the UK, gales are rare
The strongest wind recorded in Australia is over 400 km/h and in England it was nearly 230 km/h

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9
Q

Extreme weather caused by tropical storms - extreme winds

A

strong winds in tropical storms caused by area of very low pressure in the centre that creates a big pressure difference to surrounding area
winds can have speeds of more than 250 km/h
winds are strong enough to damage or destroy buildings + plants and cause loose objects like bins to be picked up and transported

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10
Q

Extreme weather caused by tropical storms - extreme rain

A

High rainfall is caused by large amounts of warm, moist air being sucked towards centre of storm due to pressure difference - as this happens, air rises, cools and condenses, causing rain
Can be enough rainfall to cause floods and landslides

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11
Q

Normal conditions

A

Low pressure in West - air rises causing rain + storms (Australia)
Trade winds blow WEST and wind high in atmosphere blows EAST
High pressure in East - air sinks causing clear skies + dry weather (South America)
Cold water rises in East
Warm surface water + strong currents from East to West

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12
Q

El Nino

A

(every 3-4 years)
High pressure in West - air sinks causing clear skies and droughts (Australia)
Trade winds blow EAST and wind high in atmosphere blows WEST
Low pressure in East - air rises causing rain, storms and floods (South America)
Cold water stops rising in East
Warm surface water + currents are weaker or in opposite direction than normal

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13
Q

La Nina

A

(occurs every 2-7 years)
Normal conditions become extreme
Trade winds blow stronger to West and more cold water rises in East
More heavy rainfall + floods in West and less rainfall + droughts in East

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14
Q

Distribution of Tropical Storms

A

(has stayed similar over time)
Most occur between 5° - 30° N/S of equator - any further and the water isn’t warm enough
Majority of storms occur in the N.Hemisphere (especially over Pacific Ocean) in late summer - autumn as the sea temps are the highest

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15
Q

Frequency of Tropical Storms

A

(has varied over time)
Number varies each year
In the Atlantic Ocean, the number of storms per year has increased since 1984 with no regular pattern

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16
Q

Distribution of Drought

A

(has varied over time)
Areas most at risk - central + southern Africa, Middle East, Australia, eastern S.America + parts of N.America
Since 1950, there have been more droughts in Africa, Asia + Mediterranean and less in the Americas + Russia

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17
Q

Frequency of Drought

A

(hasn’t changed very much over time)
Global frequency has varied from year to year with no overall change since 1950
Some scientists have suggested that droughts could become more frequent + severe in future due to climate change

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18
Q

Causes of Drought

A
  1. Changes in Atmospheric Circulation (e.g. El Nino or La Nina) - means it doesn’t rain much in an area for months or years
  2. Changes in Atmospheric Circulation can also make annual rains fail
  3. High pressure weather systems (anticyclones) block weather systems that cause rain (depressions)
19
Q

Extreme Weather Flash Flood Case Study - Boscastle 2004 - Causes

A

Low pressure system brough warm moist air that rose causing intense rainfall. 2 months worth of rain fell in 2 hours
Boscastle was prone to flash floods as it had steep sides and impermeable rock as its ground.
The town was also built on a floodplain. The steep sided valley caused water to run down quickly and the ground being impermeable meant that it could not absorb water
Some human causes include there being no flood barriers and an old sewage drainage system that became full very quickly

20
Q

Extreme Weather Flash Flood Case Study - Boscastle 2004 - Consequences

A

58 properties were damaged with 6 being destroyed
£2 million worth of damage was caused
Tourism industry was devastated - 90% of Boscastle’s income comes from Tourism
The flood happened so quickly that people could not evacuate in time or move their belongings to a safer place. This meant that 1 person was seriously injured while many suffered mental health problems after the flood due to stress relating to flood

21
Q

Australia’s Drought 2005 - 2008 - Consequences

A

Drought hit Murray Darling Basin the hardest. Due to the drought the River Murray dried up and was 50% below normal level
Over 100,000 people employed in farming lost their jobs. 13 dairy farms closed down
Energy and water prices increased
Crop yield fell as there was a lack of water
Caused wildfires with 8 people killed. 30,000km^2 of forest burned down

21
Q

Extreme Weather Flash Flood Case Study - Boscastle 2004 - Responses

A

£4.5 million dedicated to flood defence scheme
Over 150 people airlifted by 7 helicopters
1850 tonnes of debris was cleared while homes, businesses and roads were eventually rebuilt
Floodwalls and river banks were raised

21
Q

Australia’s Drought 2005 - 2008 - Causes

A

Australia is located below a high pressure belt causing naturally low rainfall
Australia is flat and large therefore receives no relief rainfall
El Nino - trade wind moved east cause high pressure in Australia therefore causing droughts
The temperature was higher in this period leading to increased water evaporation
Some human causes include mismanagement of water resources. Each Australian drinks 1 million litres of water per year.

22
Q

Structure of the earth

A

Inner core - ball of solid iron and nickel
Outer core - liquid iron and nickel
Mantle - slow-moving semi-molten rock
Crust- 10-70km thick and is divided into tectonic plates

Tectonic plates made of 2 types of crust - continental + oceanic
Continental - thicker + less dense
Oceanic - thinner + more dense

22
Q

Australia’s Drought 2005 - 2008 - Response

A

Government dedicates $10 billion to national water management plan in 2007
Government provided many families and small businesses with support
Drought resistant crops introduced
Water conservation measures were introduced. People who relied on the River Murray for their water supply had their allocation reduced
Cities like Sydney built desalination plants that can turn seawater into drinkable water

23
Q

Convection currents - how tectonic plates move

A

Lower parts of mantle are sometimes hotter than upper parts - when lower parts heat up they become less dense and rise
As they move towards top of mantle they cool, become more dense, and sink
These circular movements are called convection currents - cause tectonic plates to move

24
Q

Destructive Plate Boundaries

A

Where oceanic and continental plates are moving towards each other
Denser oceanic plate is forced down into mantle and destroyed
This creates volcanoes and ocean trenches

25
Q

Collision Plate Boundaries

A

2 continental plates moving towards each other
Both plates are folded and forced upwards
This creates fold mountains

26
Q

Constructive Plate Boundaries

A

Where 2 plates are moving away from each other
Magma rises from the mantle to fill the gap and cools, creating new crust

27
Q

Conservative Plate Boundaries

A

Where 2 plates are moving sideways past each other or are moving in same direction at different speeds
Crust isn’t created or destroyed

28
Q

Shallow-focus earthquakes

A

Are caused by tectonic plates moving at or near the surface
They have a focus of 0-70km below the surface

29
Q

Deep-focus earthquakes

A

Are caused by crust that has previously been subducted into mantle moving towards centre of earth, heating up or decomposing
Focus between 70-700km below the surface

30
Q

Composite volcanoes

A

Occur at destructive plate boundaries
Subducted oceanic crust contains water which causes the subducted crust to erupt
Eruptions start with ashy explosions that deposit a layer of ash, then erupt a layer of thick, sticky lava that can’t flow
Forms a steep-sided cone

31
Q

Shield volcanoes

A

Occur at hotspots or constructive plate boundaries
Not very explosive and made up of only lava
Runny lava that flows quickly and spreads over a large area
Forms a low, gentle-sided volcano

32
Q

Hotspots

A

A bit of the earths crust that is hotter than normal
Occur when a plume of hot magma from mantle moves towards surface, causing large flow of heat from mantle to crust
Magma can sometimes break through crust and reach surface causing an eruption and a volcano forms
They remain stationary over time, but crust moves above them which can create chains of volcanic islands

33
Q

Causes of Haiti earthquake

A

Buildings made from cheap material such as concrete blocks with cement. This meant houses fell apart
Lack of government funding, no pipe supply network
One of the poorest countries in the world, not enough money for good infrastructure
There are mainly natural causes though. These are the North American plate being subducted below the Caribbean Plate
Enriquillo Plantain Garden Fault specifically was the main issue
It was a shallow focus earthquake therefore the effects were felt, the energy waves did not have time to dissipate only 13 km below the ground

34
Q

Consequences of Haiti earthquake

A

220,000 people killed with 300,000 injured
1.3 million people homeless
30,000 buildings destroyed and a ⅓ of the city destroyed
80% of the people now lived below the poverty line. It was 50% before
Cholera cases spread rapidly due to poor sanitation conditions. 600,000 cases
Civilians were stuck in campsites as they were too poor

35
Q

Short-term responses to Haiti earthquake

A

NGO’s built temporary tents and hospitals
Haiti government and NGOs set up camps for 1 millions displaced people
Organised water supplies for those in need

36
Q

Medium-term responses to Haiti earthquake

A

Oxfam sets up emergency treatment centres
Oxfam gives food and sets up canteens for the displaced

37
Q

Long-term responses to Haiti earthquake

A

Unicef sets up schools and practises earthquake drills
Government builds new quake resistant housing although far away from the city therefore many people take a long time to get to work
Permanent water pumps created by NGOs
Awareness raised about Cholera in school

38
Q

Predicting earthquakes

A

Seismometers used to pick up vibrations in the earth’s crust. More vibrations indicate a higher possibility of earthquake
Laser beams used to monitor plate activity
Early warning systems means warnings can be communicated quickly using the internet and SMS. People will have enough time to grab essentials, turn off gas and get under cover
Seismometers and lasers can only give a few seconds or minutes of warning

39
Q

Protecting against earthquakes

A

Pendulum in skyscrapers, massive ball acts like a pendulum during earthquakes. This counteracts the forces of the earthquake’s waves. Seen in Taipei 101 tower
Buildings built on reinforced concrete and have special foundations

40
Q

Preparing for earthquakes

A

Japan urges the citizens to make grab bags with essential things to survive an earthquake

Geography GCSE (7 decks)

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