GCSE Physical Geography: Hazards

A natural event (for example earthquake, volcanic eruption, tropical storm, flood) that threatens people or has the potential to cause damage, destruction and death. An event needs the interaction of people to make it a hazard.

Hazards that form due to influences in the atmosphere, by the movement of air and water.

Hazards that occur on the earth’s surface.

Hazards that form due to the movement of tectonic plates in the earth’s crust.

Any biological substance that poses a threat to the health of people, e.g. viruses

Determines how much money is available to prepare for the event and predict the hazard.

• HICs can afford the technology to predict events and broadcast the disaster so that people can evacuate in time.

• HICs can also afford better infrastructure which leads to less chance of death and damage.

• HICs have better access to emergency resources and help.

The more often a hazard occurs, the more likely people are prepared, which leads to less deaths as people know how to stay safe during the disaster.

Infrastructure and lifestyles can be adapted in areas of high frequency, lowering risk of damage.

Emergency services are also more likely to be prepared for hazards in high frequency areas, reducing death risks.

The boundary or margin between two tectonic plates

Inner core- solid

Outer core- liquid

Mantle- Molten liquid

Crust- Solid

Oceanic crust (under oceans)- thinner, heavier and denser, newer material

Continental crust (under land)- thicker, lighter and older material

(oceanic crust is like a thin sheet of metal, while continental crust is a big block of cardboard)

• Heat from the core heats material in the mantle, and causes magma to rise (hot air rises).

• The magma rises towards the top of the mantle, and sinks towards the lower part of the mantle when it cools.

• Magma pulls/pushes the crust when it drags along the top of the mantle and sinks back down.

• This process repeats to form a convection current.

Slab pull- Destructive plate boundary

• Dense oceanic crust is being PULLED by gravity into the mantle.

• The oceanic plate is subducted underneath the continental plate and sinks into the mantle.

Ridge push- Constructive plate boundary

• Magma rises from mantle as plates move apart and solidifies to form new land.

• This new land PUSHES the crust away from the plate margin.

Patterns in the distribution of earthquakes and volcanoes match where plate margins are located.

The large band of volcanoes and earthquakes which circles the pacific ocean is known as the Ring of Fire.

Earthquakes and volcanoes can occur in the middle of plates too, in areas known as hot spots.

For example, Hawaii is located on a hot spot far from the edge of the Pacific plate.

The point where the pressure is released within the earth’s crust.

The point on the earth’s surface directly above the focus.

Shockwaves that spread out from the focus of an earthquake.

The further away from the focus, the lower the strength of the waves.

The closer to the earth’s surface the focus is, the stronger the seismic waves will be.

If the focus is lower down in the crust, the shockwaves will be less powerful and would have less of an impact.

• Two plates move apart.

• Hot molten magma rises to fill the gap.

• Magma cools and solifies constructing new land.

Example- Mid-Atlantic ridge

Eurasian plate moves away from the North American plate.

Constructive plate margins lead to gentle volcanoes where the magma erups onto the surface, forming a volcano with gentle slopes.

Earthquakes are caused by the movement of magma through the crust.

Two plates move towards each other and collide.

If two continental plates collide, they are both light and cannot sink into the mantle. Compression forces the plates to collide and form fold mountains.

If an oceanic and continental plate collide, the denser oceanic plate is subducted under the continental plate as the oceanic crust is thinner and heavier.

Example- Nazca plate collides with the South American plate

As the oceanic plate is subducted under the continental plate, the oceanic crust melts due to heat in the mantle. Hot magma rises through gaps in the crust, causing explosive volcanoes.

When the two plates converge, friction and pressure builds as the crusts scrape against each other. The rocks eventually fracture and release pressure, causing an earthquake.

Two plates slide parallel to each other. This can be in the same direction at different speeds or in the opposite direction to each other. It doesn’t matter. Nor does it matter whether they are oceanic or continental crust.

Example- San Andreas Fault, USA.

North American plate and Pacific plate slide past each other.

As plates slide, friction and pressure builds. This pressure is suddenly released, causing an earthquake.

Volcanoes are not formed at conservative plate margins. Magma cannot rise as there is no gap created between the tectonic plates, nor any plate being subducted into the mantle.

The immediate damage caused as a direct result of a tectonic hazard, e.g. deaths, destruction of buildings

Consequences of tectonic hazards that occur later and indirectly as a result of the initial disaster, e.g. reduced tourism, aftershocks.

An example of a tectonic hazard in a high income country is the 6.3 magnitude earthquake in L’aquila Italy.

• As a direct result of the earthquake, 300 people were killed. (social)

• Culturally significant buildings were destroyed, including the National Museum

  • Social- tourism reduced

  • Economic- cost of damage

• Hospital was damaged, patients had to be evacuated to someplace else as the damage in the hospital was too severe to treat injured victims

  • Social- death/injuries

  • Economic- cost of damage

• Aftershocks triggered landslides

  • Economic- caused damage to housing and transport

• Number of students at L’aquila university decreased

• Lack of housing for residents meant house prices and rents increased

• Reduced amount of business, tourism and income

Immediate responses

• Electricity and Gas bills were suspended

• Free mobile cells were handed to people who had lost their homes

• Emergency camps were set up providing water and medical care

• Ambulances and fire engines were sent in to rescue survivors

Long term responses

• Free public transport and discounts on educational support for students

• Historic centres were expected to take 15 years to rebuild

• An investigation into why modern buildings weren’t able to withstand the earthquake

An example of a tectonic hazard in a low income country is the 7.8 magnitude earthquake in Gorkha in Nepal.

• 1 million were made homeless

• Historic buildings and temples collapsed

  • Economic- reduced tourism and cost of rebuilding

• 50% of schools were destroyed

  • Social impacts on education and literacy rate in the long term

• A reduction in tourism, employment and income to Nepal

• Rice stored in homes was ruined in the rubble

  • Social- caused food shortages and income losses

  • 2/3 of population depend on farming

Immediate responses

• Emergency shelters providing medical care and water to survivors

  • Medical care was crucial as the earthquake was during the monsoon season, increasing the risk of waterborne diseases

• Several companies did not charge for telephone calls in the days after the earthquake

Long term responses

• Tourism Ministry had extended Mount Everest climbing permits to encourage people back in an attempt to boost tourism

• Rebuilding of houses, roads, schools

• Heritage sites reopened in time for the tourism season

These factors explain the varying effects and responses between the LIC Gorkha and HIC L’aquila earthquake

Medical facilities- The more medical resources, the easier for victims to get treatment.

Transport infrastructure- The better the transport network, the quicker it is to evacuate and for aid to arrive

Population density- The more people, the more potential for risk of injuries and fatalities

Construction standards- Buildings with strict regulations are more secure and have less chance of collapsing

Distance from epicentre- The closeer to the epicentre, the greater the magnitude will be

Time and day- Buildings and roads that collapse when they are empty reduce casualties, e.g. more schoolchildren would have died if a school collapses on a weekday

Resources and finance- The more resources and money available, the quicker it is to rebuild homes and hospitals

• Farming- Volcanic areas have very fertile soil that is rich in nutrients and good for farming

  • land can be farmed productively in these areas to provide a source of food and income

• Mining- Valuable minerals are found in volcanically active areas

  • Despite being dangerous, mining provides an income

• Family/Income in LICs- People in LICs cannot afford to move due to lack of transport/expensive accomodation elsewhere/cannot leave family behind

• Tourism- Tourists visit volcanoes for spectacular views

  • 100 million people visit volcanic sites every year

  • Tourism gives good income for local people

• Preparation- Some places are well prepared for hazards so residents feel safe

Recording physical changes, e.g. earthquake tremors, to forecase when and where a natural hazard might strike

Actions taken before a hazard strikes to reduce its impact, e.g. educating people or improving building design

Preparing actions during and recovering from a disaster, enabling communities and authorities to act quickly and without chaos, e.g. emergency evacuation plans

• Seismometers measure tremors or shocks that occur before the big earthquake

• Mapping earthquake locations and times to predict when the next earthquake will occur by spotting patterns in the data

• Thermal heat sensors detect changes in the temperature of a volcano’s surface

• Tiltmeters measure ground deformation that signals magma collecting near the surface, predicting a volcano

• Preparing emergency aid supplies so that food, water, medicine and shelter are accessed faster

• Earthquake drills reducing chaos and confusion and ensuring people evacuate safely and quickly during the disaster

• Exclusion zones preventing people from entering vulnerable areas near active volcanoes

• Designing earthquake resistant buildings with reinforcements to prevent collapse, withstand seismic waves and minimise damage

  • Fire resistant materials

  • Shock-absorbing foundations

  • Shatterproof glass

• Education on how to prevent futher injury and the dangers of volcanoes

  • Buildings cannot be designed to withstand lahars (mudflows) and lavaflows, so education on how to lookout for these dangers is the best protection

Exposure to the sun’s rays; the amount of solar radiation reaching a given area on the earth’s surface

A worldwide system of winds moving heat FROM the equator TO the poles in order to reach a balance in temperature.

Winds are large scale movements of air due to differences in air pressure.

Air always moves from high pressure to low pressure, and this movement of air generates wind.

This pressure difference is because the sun heats the earth’s surface unevenly. Insolation at the equator is greater than the insolation at the poles due to the angle of the earth’s tilt.

Hot air rises and cool air sinks through the process of convection.

The irregular heating of the earth’s surface creates pressure cells, each generating different weather patterns.

Each hemisphere has three cells (the Hadley cell, Ferrel cell, and Polar cell) which circulates air from the surface through the atmosphere and back.

The air redistributes energy around the world so that the equator and poles are habitable and not recieving/losing too much heat.

Hot air rises

Cold air falls

Low pressure areas due to hot rising air

High pressure areas due to cold sinking air

Low pressure = thick clouds, high rainfall

High pressure = hot dry clouds, low rainfall

Surface winds move from high pressure areas to low pressure areas

High amounts of insolation near the equator, making it a low pressure zone where there is lots of rising air, forming thick clouds which rise, cool, and condensation occurs, causing lots of heavy rainfall.

The Hadley cell extends from the equator to between 30 and 40 degrees north and south

1. At the equator, insolation causes air to rise, creating a low pressure zone the earth’s surface

2. As the air rises, it cools and sinks

3. The sinking air forms a subtropical high-pressure zone

4. The air becomes warmer and drier as it sinks, creating an area of little cloud and low rainfall where deserts are found

5. The air flows back towards the equator as trade winds

The Ferrel cell occurs from the edge of the Hadley cell to between 60 and 30 degrees north and south of the equator

1. Air on the surface is pulled towards the poles

2. The winds pick up moisture as they travel over the oceans

3. They meet cold air that has drifted from the poles

4. The warmer air from the tropics is lighter than the cold polar air, so the warmer air rises

5. This causes a low pressure zone near the surface as the warm air rises, causing unstable weather conditions and wet and windy weather

The Polar cell occurs at 60 degrees north and south

1. At the poles, air is cooled and sinks towards the ground, creating an zone of high pressure

2. It flows towards the lower latitudes

3. Here, the cold air mixes with the warmer tropical air and rises, creating a zone of low pressure

4. This causes unstable weather conditions

The Coriolis effect is the appearance that the global winds and ocean currents curve as they flow, due to the Earth’s rotation on its axis, forcing the winds to blow diagonally.

In the northern hemisphere, it curves the winds to the right

In the southern hemisphere, it curves the winds to the left

A tropical storm is an intense destructive rotating low pressure system which forms in the tropics and results in strong winds and heavy rainfall.

The tropical storm has a different name where it occurs.

In US- hurricanes

In South Asia- cyclones

In East Asia- typhoons

They form in the tropics

5-20 degrees north and south of the equator

• Warm ocean water temperatures

• 5-20 north and south of the equator

  • any closer and there is not enough spin from the rotation of the earth

  • the Coriolis effect causes the storm to spin, causing a rotating mass of clouds

• Tropical regions- warm temperatures where insolation is high

• Low pressure areas where warm air is converging and rising rapidly

• Circular shape

• Bands of swirling cloud/circling storm clouds

• Eye

• Eye wall

• Central eye of the storm where there is no cloud

1. Hot sea temperatures cause warm air to rise quickly

2. This creates an intense low pressure zone

3. The rising air draws further warm air up from the ocean’s surface, generating stronger winds

4. The air spirals upwards, cools and condenses to form large clouds

5. The rotation of the earth on its axis sets up a spinning motion

6. These clouds form the eye wall of the cyclone and produce heavy rainfall and the strongest winds

7. In the centre of the storm, cool air sinks, creating calm and dry conditions known as the eye of the storm

8. The storm is carried across the ocean by the prevailing winds, picking up more moisture across the sea as it moves, becoming more powerful

9. Tropical storms die out when they reach land as the heat energy and moisture from the ocean are no longer available to drive the storm

The Coriolis effect makes low pressure systems spin anti-clockwise in the Northern hemisphere, and clockwise in the Southern hemisphere.

• Storm surges

• Strong winds that can tear off roofs, break windows and damage communication and transport networks

• Torrential rain and flooding- the warm humid air from cyclones produces huge amounts of rainfall and flooding as the cyclone moves inland

Frequency and Distribution

• More of the world’s oceans will have higher temperatures as a result of global warming, so more places across the world will experience tropical storms.

• Warmer oceans means tropical storms will affect areas further north and south of the equator

  • more low-lying coasts are at higher risk

• Oceans will stay at high temperatures for longer during the year, increasing the frequency of tropical storms

Intensity

• Higher temperatures increase the wind speed, causing storms to be stronger and cause more damage

• Estimated to have a higher number of category 4 and 5 storms

The global distribution of tropical storms is related to the general atmospheric circulation that transports heat from tropic to polar latitudes.

• Tropical storms develop in the tropics on the low pressure zone around the Equator

  • once they gain energy, they can travel further away from the equator

  • they cannot develop directly on the equator because the Coriolis effect is not strong enough and is needed for tropical storms to spin

Primary effects are immediate impacts of strong winds, high rainfall and storm surges (storm surges are when the sea level rises rapidly)

Secondary effects are the impacts that occur later on after the storm has passed.

• High wind speeds destroy infrastructure such as electricity power lines, houses and villages and can out crops

• Torrential rainfall can result in extensive widespread flooding

Amount of destruction depends on storm’s strength and how well people are prepared and protected.

• Damage to houses can force people to live in temporary shelters

• Lack of shelters/overcrowded shelters can cause distress, homelessness and death

• Cost of rebuilding homes are expensive

• Blocked or destroyed roads prevent emergency vehicles and aid from getting through

• Hospitals, shops and homes won’t have a power supply

• Damage to crops can cause shortage of food, increased food prices and famine

• Flooding can cause drowning or injuries

• Potential unemployment from economic impact and destruction of businesses and infrastructure

• Warning systems broadcast information to the public

• Evacuation to higher ground or emergency storm shelters away from the impacts of storm surges

• Distributing emergency food and water to survivors

• Repairing damge to existing buildings and infrastructure

• Ensuring the country is capable of managing a future hazard by investing in methods of protection and prediction, e.g. new sea defences or a new warning system

Typhoon Haiyan was a category 5 storm that struck the Philippines in 2013 with wind speeds of over 315 km/h.

• Over 6000 people died

• High wind speeds

  • Interrupted power supplies, damaged infrastructure, blocked roads with trees and debris

• Heavy rainfall flooded 1km inland

• 1 million houses were destroyed- temporary shelters overcrowding, poverty and distress

• Flooding caused groundwater supplies to be contaminated with sewage

  • increased risk of waterborne diseases such as cholera

  • low sanitation, pressure on damaged hospitals as less people had access to clean water

  • contaminated fishing waters- impact on industry, local employment and food shortages/food prices

    • more people fought for food, stampedes for rice supplies

• Authorities evacuated 800,000 people with many seeking refuge in a stadium

• Emergency aid supplies arrived once the airport was reopened

• A curfew was imposed 2 days after the typhoon to stop looting

• Food packs and water were distributed

• Scheme to upgrade buildings when rebuilding to defend better against future disasters

• A new storm surge warning system for citizens to evacuate in time

• Satellites- tropical storms have an identifiable cloud pattern that satellites monitor

• Wind strength can be monitored by measuring wind speed

• National Weather service can announce a warning when storm winds are detected

Monitoring and Prediction alerts people and gives them time to prepare and evacuate.

Many LICs are less able to monitor and predict tropical storms as the equipment is very expensive.

• Governments can plan evacuation routes to get people away from tropical storms quickly and safely

• People are encouraged to stock up on food and water as they may be trapped in their homes following a storm

• Training and education on the impacts of storms and how to reduce injuries during a storm

• Emergency services doing storm drills

• Installing warning loudspeakers

• Designated emergency shelters on stilts to protect from storm surges

Buildings are less likely to collapse, less people will die from collapsing buildings and falling debris

• Storm shutters on windows to reduce flying debris

• Defences such as sea walls and stilted buildings to prevent damage from storm surges

• Bicycles nearby to give warnings to remote communities

• Lack of trees nearby buildings to reduce damage if uprooted

Protection can be expensive to put in place, but saves money in the long term as there is less need for rebuilding

• Heavy rain

  • Risk of flooding- damage to homes, disrupts transport networks

• Wind

  • Uprooted trees and debris can injure or kill

• Thunderstorm

  • Can cause fires

  • Lightening strikes damage property and environment

  • May disrupt daily life if people are afraid to leave home

• Hailstorm

  • Makes driving difficult- can damage windscreens

  • Can damage property and destroy crops

• Drought

  • Insufficient water for crop production- high food prices, risk of famine

  • Low water reserves in resevoirs- hosepipe bans and water supply restrictions distress people

• Snow/Ice

  • School, transport and business closures

  • Injury through slips and falls

  • Damages crops and wildlife

  • Disrupts transport networks

  • Risk of hypothermia

An example of a recent extreme weather event in the UK were the Somerset Levels Floods in 2014. Somerset is an area of low-lying farmland in south-west England. It had been developed for farming and residents, so many people were at high risk from the flood event.

Very high rainfall, 100mm above average

• over 600 houses flood

  • residents evacuated to temporary accomodation

• restricted access to flooded villages

  • impacting daily lives (schools, shopping)

• Power supplies cut off

• cost of repair estimated over £10 million

• livestock evacuated from flood zone

  • impacting farming industry and food prices

• local roads drenched in floods

  • impacting tourism and trade

• huge amount of debris needed to be cleared

• waters contaminated with sewage and chemical pollutants

• Emergency aid to rescue victims and treat survivors

• Villagers used boats to attend school and go shopping

• Local community groups gave supplies and support

• Somerset Country launched a £20 million action plan to prepare for future extreme floods

• Vulnerable communities will have flood defences

• Road levels are raised to maintain communication and allow business to continue during future flood events

The last 2.6 million years where there was a global drop in temperature and a gradual cooling with warmer interglacial periods.

Climate change is a long-term change in the earth’s climate due to an increase or decrease in the average atmospheric temperature.

Global warming is the recent trend of an increase in average global temperature.

• Ice cores can be drilled to find information about the climate when the snow fell

• In Antarctica there are no permanent residents, so the layers of snow remain unaltered

  • The layers hold information about climate change as they build up over the Quaternary period

  • When ice cores are melted, trapped CO2 is released, which can be compared to present levels to see the extent of climate change

• Ocean sediments are sediments deposited at the bottom of the sea

• Organisms and remains of plankton in the sediment reveal information such as past surface water temperatures and levels of oxygen and nutrients through the Quaternary period

• The deeper the sediment, the older it is

• The oxygen isotopes in ocean sediments can be used to calculate the temperature

These methods are not reliable because they only indicate climate change rather than provide direct evidence of accurate temperature.

A more reliable method would be measuring the size of ice sheets and glaciers to analyse thermal expansion and melting.

• Shrinking glaciers and melting ice

  • Arctic sea ice has melted by 65%

• Rising sea levels

  • Due to rising temperatures causing meltwater from glaciers to flow to seas

  • Average global sea level risen by 10cm in past 100 years

• Shorter hibernations

• Plant flowering patterns changing

The solar radiation recieved by the earth changes depending on its orbit.

• The earth’s orbit is elliptical, so as the earth orbits closer to the sun, the climate gets warmer.

• The tilt of the earth’s axis changes every few thousand years. The greater the tilt, the more exaggerated the climate- hotter summers and colder winters

• The earth is not a perfect sphere, so it wobbles on its axis, affecting seasonal temperatures

The output of the sun is measured by observing sunspots on its surface. Sunspot activity dictates the heat given by the sun.

Increased sunspot activity leads to hotter temperatures,

e.g. very few sunspots were observed by satellites during colder periods

Violent volcanic eruptions blast huge quanities of ash, gases and liquids into the atmosphere.

• Volcanic ash clouds can block out the sun, reducing temperatures on the earth as a short-term impact.

• Sulphur droplets can reflect radiation and reduce solar radiation entering the earth’s atmosphere.

This is called volcanic winter.

Carbon dioxide

Nitrous oxide

Methane

Water Vapour

Carbon dioxide- respiration, volcanic eruptions

Nitrous oxide- soils and oceans

Methane- emitted from soils due to decomposition

Water Vapour- evaporated from oceans and plant leaves

The impact on the climate from the additional heat retained due to the increased amounts of greenhouse gases that humans have released into the earth’s atmosphere.

The greenhouse effect is needed to make earth livable. The enhanced greenhouse effect is being caused by the incease of greenhouse gas emissions and is leading to global warming.

1. Sun emits solar radiation

2. The earth absorbs most of the radiation and emits it as infrared radiation

3. Some infrared radiation is reflected back into space

4. Some infrared radiation is trapped in the earth’s atmosphere by greenhouse gases

1. Sun emits solar radiation

2. The earth absorbs most of the radiation and emits it as infrared radiation

3. Less of the sun’s energy is reflected back out to space as there is a bigger layer of greenhouse gases

4. More energy is trapped in the earth’s atmosphere by greenhouse gases, making it hotter

Burning fossil fuels releases carbon dioxide into the atmosphere, accounting for over 50% of global greenhouse gas emissions.

Fossil fuels are used in transport, generating electricity, heating and manafacturing.

As the world’s population grows and wealth increases, people are demanding more and more energy, increasing the amount of fossil fuels burned and therefore CO2 released.

Agriculture accounts for over 20% of global greenhouse gas emissions.

• Cattle ranching produces large amounts of methane.

• Deforestation to clear land for crops leads to less CO2 being absorbed during photosynthesis.

• The production of feritilisers produces fossil fuels.

Food demand is increasing with population, and rising wealth increases meet demand. Therefore, large-scale agriculture will continue to play a huge role in causing climate change.

Deforestation clears forests on a huge scale, with the destruction of these carbon sinks causing less CO2 to be absorbed during photosynthesis, and releasing CO2 when the carbon sinks are burned.

Deforestation occurs due to:

• clear land for agriculture so that farmers have space to plant crops and graze livestock

• logging for wood

• building roads to access remote areas

• making room for the expansion of urban areas

• Hotter temperatures lead to heat strokes and dehydration becoming more frequent

  • more money spent on healthcare than improving quality of life

• Fewer winter related deaths due to milder winters

• Increased flooding due to sea level rise leads to displacement of huge numbers of people

• More deaths related to extreme weather, e.g. more tropical storms → higher death rate