Paper 1: A: The Challenge of Natural Hazards

Natural Hazards

What are natural hazards?

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Natural hazards are physical (natural) events that have the potential to do damage to humans and property.

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Tectonic hazards

How can different factors affect hazard risk?

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• Population growth - higher numbers of people at risk e.g. Rural vs Urban
• Climate change - increasing frequency & magnitude of hazards
• Deforestation - increases risk of desertification and flooding
• Wealth - LICs do not have the money or expertise for management
• Physical Geography e.g. mountains can limit access, islands can be hit by tsunamis unlike landlocked areas.

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These can trigger secondary hazards:

Tsunamis

Volcanoes - composite and shield

Earthquakes

Weather hazards

Tropical Storms

(Hurricanes, Typhoons)

Drought

Floods

(River and Coastal)

Forest Fires

Landslides

Avalanches

P1 Section A: Tectonic Hazards

What are tectonic plates and why do they move?

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• Tectonic plates are pieces of the Earth’s crust/lithosphere.
• There are two theories as to why tectonic plates move:

1. Convection currents

In the mantle, driven by heat (up to 5000^oC) generated in the inner core by the radioactive decay of uranium. Heated magma rises as it is a lower density to create constructive boundaries before cooling and sinking to create a destructive boundary.

2. Ridge push & Slab Pull:

At constructive margins molten magma rises as plates push apart, forming ocean ridges. As the molten magma slides down from the ridge it pushes the plates apart.

At destructive margins the denser plate/slab sinks back into the mantle under gravity, pulling the rest of the plate behind it.

Distribution - Earthquakes - along all three types of plate boundary (constructive, destructive, conservative) with the highest magnitude deep focus earthquakes on destructive boundaries.

Anomalies= hotspots like Hawaii.

Distribution- Volcanoes: Along constructive plate boundaries e.g. Mid-atlantic ridge. Along destructive plate boundaries e.g. Pacific Ring of Fire. Hotspots e.g. Hawaii, where magma rises mid-plate through thinner areas of crust.

Layers

Distribution

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Destructive Plate Margins

Describe the physical processes taking place at this types of plate margin that lead to earthquakes and volcanic activity [sequence question]

I have studied Japan earthquake 2011 as a destructive place example

1. At a destructive plate margin two plates are moving towards each other due to sinking convection currents in the mantle and due to slab pull.
2. When an oceanic and a continental plate meet, the denser the oceanic plate is subducted underneath the lighter continental plate.
3. As the denser oceanic plate subducts (sinks) into the mantle it melts creating explosive acid (andesitic) magma.
4. Friction as plates push into each other causes pressure build up.
5. A sudden release of the tension triggers an earthquake from a point underground called the focus.
6. The seismic waves released cause the strongest vibrations at the point on the surface directly above the focus called the epicentre.
7. This can cause the magma to rise through the crust to form steep sided, explosive composite volcanoes.

Constructive Plate Margins

Describe the physical processes taking place at this types of plate margin that lead to earthquakes and volcanic activity [sequence question]

I have studied the mid- Atlantic ridge in Iceland as an example of a constructive plate margin.

1. At a constructive plate margin two plates are pushing away from each other due to rising convection currents in the mantle and due to ridge push.
2. This usually takes place under the oceans as oceanic plates push apart.
3. Friction as plates pull apart from each other causes pressure build up.
4. A sudden release of the tension triggers an earthquake from a point underground called the focus.
5. As the two plates move apart a gap is created between the plates which is filled by rising basic (basaltic) magma also creating small earthquakes as magma forces its way through, spreading the gap.
6. Layers of this runny (low viscosity) magma flow out on the surface as lava and solidify to create gently erupting, wide based shield volcanoes.

Conservative Plate Margins

Describe the physical processes taking place at this types of plate margin that lead to earthquakes [no volcanoes here!]

I have studied Haiti earthquake 2010 as a conservative place example

1. At a conservative plate margin two plates are sliding past each other, either in different directions or in the same direction but at different speeds.
2. Friction as plates slide past each other causes pressure build up.
3. A sudden release of the tension triggers an earthquake from a point underground called the focus.
4. There are NO volcanoes as no magma is created or able to reach the surface..

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NAMED EXAMPLE: 2010 Haiti earthquake, a Low Income Country Named Example

How were the effects and responses affected by being a Low Income Country?

Primary (immediate) effects:

• >300,000 deaths
• 300,000 injured
• Over 250,000 homes and businesses destroyed
• Corpses rotting spreading disease
• Infrastructure (roads, port, airport) severely damaged

Secondary (long-term) effects:

• >1 million homeless for months, some for years
• 20% of jobs lost
• 8,000 died of cholera in survivors’ tented camps from untreated water

Immediate responses (hours afterwards):

• Field hospitals erected due to hospitals destroyed
• UK and USA sent search and rescue teams
• Charities (e.g. Red Cross) flew clean water in
• The Haitian government relocated homeless people to temporary tented camps
• International aid provided by fundraising

Long-Term responses (years afterwards):

• Cash for work schemes to employ people rebuilding homes
• Rebuilding - more earthquake resistant buildings
• HICs donated money to train Haitian emergency services

Higher immediate death toll due to:

• Poor quality concrete buildings and people living in slums
• Lacking of building laws
• Lack of emergency services

Years longer for recovery due to:

• Low GNI: Low Income Country
• Lack of expertise and training
• Poverty and poor economy
• Other natural disasters such as tropical storms limit development.

NAMED EXAMPLE: 2011 Japan earthquake & tsunami, a High Income Country Named Example

How were the effects and responses affected by being a High Income Country?

What were the immediate and long-term responses to this tectonic hazard?

Primary (immediate) effects:

• 16,000 deaths (93% due to drowning)
• 6,000 people injured.
• 250,000 buildings destroyed by tsunami
• Fires from broken gas pipes including an oil refinery
• Damage to Fukashima nuclear power plant triggers meltdown

Secondary (long-term) effects:

• 350,000 people homeless.
• Psychological impacts – anxiety and stress.
• Industries destroyed, trade lost (e.g. Toyota)
• $235 billion damage cost in rebuilding and lost trade

Immediate responses (hours afterwards):

• Army sent to rescue survivors.
• Evacuations to higher ground - well practiced.
• Infra-red cameras to locate bodies
• Text alerts and TV/radio warnings sent.
• Power stations on auto-shut down
• Money provided by the government.

Long-Term responses (years afterwards):

• Homes and businesses were all rebuilt within two years.
• People relocated to live away from the nuclear power plant
• Continue preparation e.g. September 1st: Annual Disaster Prevention Day

Lower immediate death toll due to:

• Earthquake proof buildings
• Tsunami gates and sea walls (however these were overtopped by larger waves than predicted)

Rapid economic recovery due to:

• High GNI: High Income Country
• Large TNCs to invest in rebuilding businesses
• However, economic impacts were more severe than Haiti as Japan is a HIC [and has more expensive infrastructure to replace]

A catastrophic magnitude 7.0 Mw earthquake struck Haiti at 16:53 local time (21:53 UTC) on Tuesday, 12 January 2010.

On 11 March 2011, at 14:46 a 9.0–9.1 Mw undersea earthquake occurred in the Pacific Ocean

You need to know both named examples and to be able to explain why one was more severe than the other.

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3Ps – Tectonic Hazards

Why do people continue to live in areas at risk from a tectonic hazard? “SWEAR”

Soil: Weathered lava creates fertile soil for crops (e.g. Indonesia)

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Warnings: many countries monitor and have evacuation plans reducing risk

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Energy: Geothermal energy - volcanic rocks are HOT so can provide heating/power

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Attractions: Tourism - opportunities for a job/income (e.g. Yellowstone NP, USA)

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Resources: Rocks are rich in minerals so valuable for mining; trade/economic growth (e.g. sulphur for matches)

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Could also be for social reasons e.g. family and community. Or they might not be able to afford to leave.

How can monitoring, prediction, protection and planning reduce the risks from a tectonic hazard e.g. earthquake or volcano?

Practice Qs for tectonic hazards:

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• Define the term natural hazard [1]
• Suggest why some areas are at higher risk of a natural hazard than others? [4]
• Describe the distribution of tectonic hazards [3]
• Explain how tectonic hazards occur on a destructive plate margin [6]
• Suggest how the impacts of tectonic hazards can be reduced [6]
• Using at least one example of a tectonic hazard you have studied, explain the primary and secondary effects of the hazard [9+3]
• Using at least one example of a tectonic hazard you have studied, assess the effectiveness of responses to the hazard [9+3]

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P1 Section A Climatic Hazards

Global Atmospheric Circulation

High Pressure = where dense cooling air sinks = dry = Deserts

e.g. the descending limbs between the Hadley and Ferrel Cells at 30^o latitude.

GAC is like the earths central heating – it moves warm air from the equator up to the poles.

There are three main cells: Hadley, Ferrel, Polar.

A Tropical Cyclone (hurricane, typhoon) is an intense low pressure weather system, which creates a rotating storm with winds over 74m.p.h. It brings hazards like torrential rain, flooding and storm surges. Storm surges being the most severe.

Low Pressure = where light warming air rises = wet = Tropical Rainforests e.g. the rising limbs of the Hadley cell on the equator

Distribution of tropical storms:

• Tropical Storms occur in areas of low pressure where warm air is rising.
• Low latitudes between 5° and 30° north and south of the equator (in the tropics) due to heat and low pressure there
• Not on the equator due to lack of Coriolis Force

Describe the global distribution of where tropical storms take place (hurricanes, cyclones, typhoons)?

Trade winds form where the two blow all year round in the same direction. They are high or low pressure depending on the cells that meet.

Low pressure on the equator 0: convectional rain = rainforests

High pressure on the tropics 30’N/S: no rain = Deserts

Low pressure 60’N [UK]: Temperate

High pressure in polar regions 90’ N/S: no rain = cold desert.

Tropical Storms:

Describe the sequence of their formation and development:

1. Thunderstorms are blown from the continent by trade winds.
2. The air is heated by warm tropical ocean (27^oC+) causing the air to rise rapidly [low pressure].
3. Strong winds form as rising air draws in more air and moisture causing torrential rain.
4. The Coriolis effect makes the storm spin, making an eye and spiralling rain bands.
5. Cold air sinks in the eye so it is clear and dry.
6. Continues supply of warm, wet air intensifies the storm.

What are the causes of tropical storms?

• Warm sea temperature above 27° C for energy and to create rapid evaporation
• 60m deep seas/oceans
• Trade winds blowing thunderstorms from the continent.
• Low pressure to ensure rising air
• Coriolis spinning force of the earth to rotate the storm

Describe the structure and features of a tropical storm:

• Calm central eye where air sinks
• Intense winds and large clouds within the eye wall where air rapidly rises
• Clouds rotating/ rain bands in an anti-clockwise direction in the northern hemisphere

Storms “die” when they make landfall because of friction with the ground/buildings etc and no longer being “charged” by the sea.

Climate change will bring Warmer air and more evaporation which means that storms might become more widespread and intense, but not necessarily as frequent.

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What were the immediate and long-term responses?

Primary (immediate) effects:

• Social: 6, 340 were killed. 28,000 injured. 1.9 million people were homeless.
• Economic: Damage cost $8billion with infrastructure and communications destroyed, affecting trade.
• Environmental: Crops were destroyed, an oil spill.

Secondary (long-term) effects:

• There were disease outbreaks due to decaying corpses and raw sewage spread by flood waters.
• Shortages of food, leading to rising food prices.
• Businesses had to close down.

Immediate responses (hours afterwards):

• Warnings were issued and people were evacuated BUT satellites are expensive so rely on USA AND false warnings before meant people ignored them
• International emergency teams brought aid like tents and blankets to survivors BUT bridges/airport destroyed so aid couldn’t get through

Long-Term responses (years afterwards):

• 'Cash for work’ schemes where people were paid by charities to help rebuild the city BUT there was corruption
• Embankments built against storm surges BUT coastline far too long and GNI too low to protect all areas in this Low Income Country

Typhoon Haiyan is a LIC, so responses were limited and they lacked the resources to prepare in the first place. The country is also made up of multiple islands which meant that access was very difficult to provide support.

NAMED EXAMPLE: Typhoon Haiyan, Phillippines (2013): Impacts and responses of tropical storms

The typhon was a category 5 tropical storm hit the Philippines on the 8^th November 2013 at 4:40am. Bringing winds of 195mph, torrential rainfall and a devastating storm surge of 7.5m

Tropical storms 3Ps:

Hurricane shelters pictured below are typical for a LIC

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P1 Section A: UK Weather:

The UK’s weather is so changeable and varied because of the “weather roundabout” it sits under. The direction the wind blows massively impacts out weather.

Examples of Extreme weather events to prove they are becoming more frequent and severe:

• Sheffield floods 2007
• Sheffield Snowfall 2009
• Sheffield 2010 
• Storm Desmond 2015
• Beast From the East 2018 
• “Pest from the west” Heatwave 2018
• Sheffield Floods 2019
• Sheffield Floods 2021
• Winter storms e.g. Eunice Feb 2022
• UK Drought and heatwave 2022

Extreme weather hazards in the UK

Extreme weather events are becoming more frequent in the UK due to climate change as:

1. More energy in the atmosphere means more intense storms.
2. Warmer temperatures = more evaporation and intense rainfall and droughts
3. Atmospheric circulation may be slowing down so extreme weather stays for longer

“Beast from the East, 2018”

-Extreme cold (sub -10^oC), frost and freezing temperatures.

-Travel disruption on icy roads, gas shortages and 10 deaths

June 2007 South Yorkshire Floods [link to rivers]

How management strategies can reduce risk:

“Heatwave and Drought, 2018”

-Extreme heat (over 30^oC) and lack of rainfall

-Hosepipe bans and heat-related deaths

Causes

Physical (natural) factors:

• Prolonged rainfall: It was the wettest June in Sheffield since records began, saturating (waterlogging) ground. Intense rainfall: 50mm on Monday 25th June
• Steep topography: Hills increasing the speed of runoff and reducing lag-time

Human factors:

• Urban Sprawl: Impermeable surfaces such as roads and driveways have increased surface runoff
• Deforestation: Without the canopy to intercept rainfall, it arrives rapidly on the ground and runs off into rivers instead of infiltrating into soil.

Flood Walls

(Hard Engineering)

£20million spent on defending Meadowhall and city centre.

Afforestation

(Soft Engineering)

Extreme weather is unexpected and severe, threatening life and property.

Other methods in Sheffield include:

Channel straightening (Sheaf, CBD)

Flood plain zoning (Rother valley and Endcliffe park)

River restoration – Woodhouse Mill

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P1 Section A Climate Change:

Solar Output – sunspots are explosions of radiation (solar storms) on the sun which last for up to 11 years. More spots = hotter

Orbital change/ Milankovitch cycle:

Changes from a circular to an oval (elliptical) orbit can affect the amount of sunlight the earth receives. It takes 100,000 years for the Earth’s orbit to change shape. This change matches closely with the alternating cold (glacial) and warm (inter-glacial) periods in the Quaternary period.

Volcanic eruption:

in the short-term volcanoes release ash which reflects the Sun’s rays causing the planet to cool. Over a long time however, eruptions can release greenhouse gases eg. CO2 causing the planet to warm.

Describe the evidence for climate change from the beginning of the Quaternary period to the present day.

Explain how natural factors cause climate change:

• The Quaternary period began 2.58 million years ago.
• This period has been characterised by glacials and interglacials

Human Causes of Climate Change

Greenhouse gases, such as carbon dioxide with makes up 50% of these gases, enhance the greenhouse effect. Methane is 10x more potent but breaks up quicker in the atmosphere.

Fossil fuels, especially coal, burned in power stations or oil for transport and industry release CO2

Agriculture e.g. cattle farming releases methane gas.

Deforestation increases the concentration of carbon dioxide in the atmosphere and reduces ability to planet to absorb carbon through photosynthesis. Trees are an example of a carbon sink where carbon is stored.

Greenhouse gases intercept outgoing radiation which increases atmospheric temperature causing global warming.

Global Warming =

the increasing temperature of the Earth

Climate Change =

long-term changes in temperature and rainfall patterns

Enhanced Greenhouse Effect =

Humans increasing the concentration of gases which trap outgoing heat

Decomposing waste in landfill sites also produce methane

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Flooding due to sea level rise

(caused by melting ice caps/glaciers and thermal expansion)

Increased frequency and intensity of tropical storms as seas warm providing more energy

Sea-ice melt leading to habitat loss for polar bears

Land-ice melting adding to sea-level and reducing albedo (reflectivity of earth)

Coral bleaching due to changes in sea-level and temperature

Drought caused by lack of rainfall leading to vegetation loss and desertification

Effects of Climate Change

Management of Climate Change

Alternative energy production will reduce CO2 production. E.g. wind, solar, hydroelectric, geothermal, nuclear

Mitigation = Actions to prevent the causes of climate change e.g. reducing greenhouse gas emissions

International Agreements e.g COP 26

100 countries:

1. Stop deforestation by 2030: as trees absorb CO2, supporting R.E.D.D

2. Shift away from coal: However, Australia, India, China and the US, haven't agreed on coal reduction.

Adaptation = Actions taken to adjust to the effects of climate change e.g. reducing damage from hazards

Reducing risk from rising sea levels would involve constructing defences such as the Thames Flood Barrier or restoring mangrove forests, or raising buildings on stilts.

Planting Trees – helps to remove carbon dioxide. [afforestation]

Increasing greenspaces, green roofs etc

Carbon Capture – takes carbon dioxide from emission sources is stored underground. Very expensive so unsustainable at the minute

Changes in agricultural systems need to react to changing rainfall and temperature patterns and threat of disease and pests.

Managing water supplies – eg. by installing water efficient devices and increasing supply through desalination plants.

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