Global Hazards 🟧1 spec point missing🟧

everything except global circulation ssytem (first spec point i think) bc that makes as much sense as liam lawson to red bull.

How do extremes of wind happen and what do they cause

• Wind is air moving from areas of high pressure to low pressure

• The greater the difference in pressure, the stronger the wind

• Extremes of wind can cause tornadoes and tropical storms

• Winds are weak in high and low pressure belts, but strong in between belts

How do extremes of temperatures happen and what do they cause

• The equator receives the most sun as the sun's rays are strongest here

• The poles receive the least sun because the rays hit the earth at an angle

• Extremes of temperature can lead to drought and heatwaves

Factors affecting temperature (2)

• Albedo is how much a surface reflects or absorbs the sun's rays

• Polar ice has high albedo, reflecting more heat -> making the poles colder

• Oceans and rainforests have low albedo -> they are warmer

• Altitude means the higher up you go, air pressure gets lower -> cooler temperatures

How do extremes of precipitation happen and what does it cause

• Areas of low pressure have high levels of precip.

• Areas of high pressure have low precip.

• Rain falls heavily around the equator

• The tropics are dry

• Too much rainfall can lead to flooding while too little can lead to drought

Describe two countries with contrasting precipitation levels

• The UK has 1150mm annual rainfall

• Australia has 465mm

• An extremely dry year for Australia will be a lot drier than one in the UK

• An extremely wet year for Australia won't be considered the same in the UK

Describe two countries with contrasting temperature

In some cities in Australia the average summer high is 33, while in the UK it is 23 An extremely warm summer in the UK is over 30 degrees, while in Australia over 40 degrees would be considered extreme

Describe two countries with contrasting wind

• Australia has much higher winds than the UK and is affected by tropical cyclones

• In the UK gales are rare

• The strongest wind ever recorded in Aus. is 407 km/h while in the UK it is only 229 km/h

Where do tropical storms usually happen

• They occur over tropical oceans and move from east to west

• They occur in the US (southern) and the Caribbean, East Asia, South Asia and Australia

Over time - Frequency of tropical storms

• Between 1950 and 1970 there was a high activity era

• Then a low activity era from 19700 to 1990

• Then a high activity from 1990 to 2010

• Scientists believe that tropical storms have been getting more frequent over time due to global warming making the oceans warmer

Where do droughts usually happen

• Areas at risk of drought are: southern Africa, sub Saharan Africa, South America, parts of Australia, and parts of the US

Frequency of drought

• Since 1940 the severity of droughts around the world have increased

• This may be due to changing rainfall and evaporation patterns

Conditions needed for tropical storms

• Ocean must be at least 60m deep and 26.5^o C

• Occur in late summer and early autumn when the oceans are at their warmest

How does a tropical storm form

1. Ocean water starts to evaporate

2. Air warms up and rises quickly

3. This creates low pressure, sucking in air from trade winds

4. Winds spiral and absorb more and more moisture from the ocean

5. Humid air forms storm clouds

6. Cool air sinks, creating an area of calm, clear conditions (the eye of the storm)

7. Light winds steer the storm

What extreme weather conditions are associated with tropical storms

Flooding and prolonged rain Storm surges High winds

What are the normal conditions in the year (not El Nino or La Nina)

Wind:

• Normally there is low pressure near Australia

• This air rises, causing rain and thunderstorms

• Wind blows east, resulting in high pressure near Peru

• Air sinks, causing clear skies and dry weather

• Trade winds blow west, starting the cycle again

Ocean:

• There is warm surface water and strong currents that go from east (Peru) to west (Australia)

• Rising cold water hits the bottom of Peru

What happens during La Nina

• Normal conditions become more extreme

• Trade winds blow to the west more strongly, and more cold water rises near Peru

• This causes more heavy rainfall and floods in the west (Australia), and less rainfall and droughts in the east (Peru)

What happens during El Nino

• Pressure rises in the west (Aus) and falls in the east (Peru)

• This means there is high pressure in the west, so air sinks, causing clear skies and droughts

• Trade winds blow east, creating low pressure in east (Peru). Air rises, causing flooding and thunderstorms

• Then winds blow west back to Aus, starting the cycle again

Ocean:

• Currents are weaker and go from Aus to Peru (opposite direction)

• There is no cold water rising around Peru

How is low pressure created and what weather is associated with it

1. When air is heated, it expands, becomes less dense and begins to rise

2. Creates low pressure at ground level

Weather = clouds, rainfall, wind

How is high pressure created and what weather comes with it

When air is cooled, it becomes less dense and begins to fall towards the ground Creates high pressure at ground level No rising air = no clouds, little rain In summer the weather is calm, sunny and hot In winter it is clear and cold

What type of winds are associated with low pressure

Strong winds

Causes of Typhoon Haiyan

Where Typhoon Haiyan formed, the ocean was over 60m deep and warmer than 26.5o There was little land to slow the typhoon down, meaning it was very powerful when it hit the Philippines Low air pressure caused a storm surge, reaching 6m in some places It got more powerful as it moved westward as it moved over warm ocean

Consequences of typhoon haiyan

Environmental

• Heavy rainfall led to flash flooding and landslides

• A barge was punctured at 85,000 litres of oil spilled into the sea

Social

• Strong winds damaged buildings

• 453 flights were cancelled

• 6300 deaths

Economic

• $2.8 billion in damages

• 74% of farmers lost their main source of income

• 571 health centres were damaged

Short term responses to typhoon haiyan

• Australia sent $28 million in aid packages

• The UN appealed for $190 million emergency aid

• WHO brought over health workers from around the world

Responses (long term)- TH

• By April 2014, services had been restored to 560 schools and 220 health centres

• 1500km of roads were repaired

• 1100km of drainage was repaired

Why was Typhoon Haiyan so devastating

• There was no land to slow it down before it reached the Philippines

• Homes were not durable

• Densely populated

• The area was still recovering from an earthquake a month prior

• Half the population live in rural areas, meaning aid took a while to reach them

Causes of UK Heatwave

• Jet stream winds were further north than usual. This meant a higher pressure weather system stayed over the UK and Europe for a long time without being moved away

• High pressure meant there was little rainfall

Consequences of UK Heatwave

Environmental

• Large wildfires e.g. In Saddlewoth Moore 18km2 was burned

• Sustained drought led to biodiversity decrease in certain species e.g. Insects

• Air quality declined

Economic

• Ice cream revenue increased by 24%

• UK economy gained $31 billion due to more people taking staycations

• Crop yields declined by 20%

Social

• 150 people had to evacuate their homes

• More people hospitalised with things like heat stroke or respiratory issues

• Water shortages and hosepipe bans

Responses of UK heatwave

• Firefighters helped tackle wildfires near Manchester

• Train operators had to impose lower speed limits so that trains would exert less force on the track

• Some track tracks were painted white to reflect the heat

Crust - thickness, makeup, how they move, type of rock

• The crust is 0-80km thick

• It is made up of continental crust (light and doesn't sink) and oceanic crust (heavy and can sink)

• Convection currents in the mantle makes the plates move

• Type of rock - basalt and granite

Mantle - thickness, temp, state of matter

• 2900 km thick

• 500-900^o C

• The rocks are molten near the core (magma) and semi molten near the crust

Outer core - type of rock, state, thickness, temp

• Made of iron and nickel

• Liquid

• 2300km thick

• 4000^o C

Inner core - type of rock, state, temp + why

• Iron and nickel

• Solid

• 5500^o C, due to radioactive decay generating energy

What is ridge push

• Ridge push occurs where new crust forms at divergent plate margins.

• The new crust is less dense than the surrounding crust, causing it to rise and form oceanic ridges.

• The older seafloor on either side slides away, moving the tectonic plates apart.

What is slab pull

• Slab pull happens at subduction zones (where older, denser tectonic plates sink into the mantle).

• As these sections sink, newer and less dense sections of the plate are pulled along behind.

What process takes place at constructive plate boundaries

• Two plates move away from each other

• Magma from the mantle rises to fill the gap, creating new crust

• An example is the Mid-Atlantic Ridge

What process takes place at destructive plate boundaries

• When two plates move towards each other

• An oceanic plate meets a continental plate

• The denser oceanic plate is forced down into the mantle and destroyed, creating volcanoes and ocean trenches

What process takes place at conservative plate boundaries

• When two plates are moving sideways past each other, or in the same direction but at different speeds

• Crust is not created or destroyed

• Example: San Andreas Fault

What process takes place at collision plate boundaries

• At collision plate boundaries, both plates are made from continental crust

• They move towards each other

• Neither plate is forced down

• Both are folded and forced up, creating fold mountains

• An example is the Himalayas

How can hot spots form volcanoes e.g. Hawaii?

• A volcanic hotspot is an area in the mantle from which heat rises as a thermal plume from deep below the crust.

• Magma rises through cracks in the crust and erupts to form volcanoes.

• As the tectonic plate moves over the stationary hot spot, the volcanoes are rafted away and new ones form in their place.

• This results in chains of volcanoes forming in a line with older volcanoes becoming dormant and then extinct as they move away from the hotspot.

How does the movement of tectonic plates cause earthquakes

• Earthquakes are caused by the tension that builds up at all four types of plate boundaries

• The plates eventually jerk past each other, sending out shock waves

• These vibrations / shock waves are the earthquake

• The shock waves spread out from the focus, so the waves nearest the focus are strongest and cause more damage

Shallow focus earthquakes - where they occur, how much they damage

• They occur at conservative boundaries, the upper part of destructive boundaries, and collision boundaries

• They are often small and cannot be felt

• Seismic waves spread out horizontally, so they cause damage over a large area

Deep focus earthquakes - where they occur, how much they damage

• They start deeper in the Earth's surface than shallow focus

• They only occur at destructive plate boundaries

• They can be very powerful, but the seismic waves spread out vertically, meaning only a small area suffers damage

Where and how do shield volcanoes occur

They occur at constructive plate boundaries, where the mantle rises to the surface as the plates pull apart This lowers the pressure on the hot rock, which partially melts and becomes runny It doesn't trap gases, so eruptions are gentle The runny law flows quickly, then cools to form a gentle slope Shield volcanoes also occur at hotspots

What is the lava and eruptions like for shield volcanoes

• Thin, runny lava

• Frequent, gentle eruptions

Where and how do composite volcanoes form

• Composite volcanoes happen at destructive plate boundaries

• The partially melted mantle that rises up is sticky

• It contains trapped sea water and hot gases - these build up pressure

• When it is released, steam and dangerous gases erupt violently

• The sticky lava cools quickly, creating steep slopes

• Ash also escapes and lands on the slopes

• Alternating layers of lava and ash create composite volcanoes

• Sometimes cooled rock forms a plug at the top of the main vent, meaning even more pressure is built up.

• This means the next eruption will be even more violent

Eruptions and lava of composite volcanoes

• Eruptions are not as frequent as shield volcanoes

• The lava is thick and sticky

• Eruptions cause pyroclastic flow

Key information about Nepal earthquake

• In April 2015, a 7.8 magnitude earthquake struck Nepal without warning

• The epicentre was in a rural district

• There was 300 aftershocks, which reached China, India and Bangladesh

Causes of Nepal earthquake

• There is a 1000km fault line that runs across the southern border of Nepal

• Indian and Eurasian plates push together by about 20mm a year

• When the plates moved suddenly in April 2015, around 100 years worth of strain was released

• It was a shallow focus earthquake (occurred 15km below the earth's surface) so the seismic waves damaged a large area

Why was Nepal affected so badly by the earthquake

• It is an LIDC so it was not well equipped

• Lots of the area affected was rural, meaning it took days for aid to reach the people there

• Hilly terrain led to lots of landslides

Consequences of earthquake

Social

• 9000 deaths

• 19 avalanche related deaths on Mount Everest

• In Bartak village only 4 of 1200 buildings were not destroyed

• 2.8 Nepalese became homeless or displaced

Environmental

• 3000 landslides - blocked roads

Economic

• The damages would have costed 35% of the country's GDP

Short term responses

• The UN helped Nepal by coordinating aid and collecting donations to support the millions of displaced citizens

• Oxfam and Red Cross supplied 50 tonnes of medical supplies

• The UK donated 51 million USD

Long term responses

• Fields were damaged so intercropping began (growing a variety of crops in the same field)

• CARE provided equipment to help reduce the amount of people who were reliant on food aid after the earthquake

• Earthquake drills were introduced

• Stricter building codes with more enforcement

How can buildings be designed to have less impact in LIDCs

• Lightweight rooves

• Cross-braced wood frame

• Steel rod foundations

How can buildings be designed to have less impact in ACs

• Deep foundations

• Safety glass to stop windows breaking

• Shock absorbers

• Cross bracing

• Damper in the roof to reduce sway

Prediction and warning systems

• Seismic gaps (areas along fault lines that haven't experienced earthquakes for a long time) are found and kept an eye on, as they are likely to be where pressure is building

• Residents can receive warnings on their phones when earthquakes hit