The challenge of Natural Hazards

Unit 1

What are Natural Hazards?

Natural hazards are physical events e.g. earthquakes and volcanoes with the potential to damage humans and property. Hazards may be tectonic e.g. Earthquakes or climatic.

E.g. Tropical storms

What affects hazard risk?

Population Density Magnitude

Relief (height of land) Time of day /year Climate change Deforestation

Wealth - LICs are particularly at risk as they do not have the money to protect themselves

Structure of the Earth

The earth has 4 layers

The inner core The outer core

The mantle The crust

The crust is split into tectonic plates.

Oceanic (thin and younger but dense & can be destroyed) Continental (old and thicker but less dense and cannot be destroyed)

These plates move and where they meet you get tectonic activity (volcanoes and

earthquakes).

The main theory of why plates move is convection currents This is heat rising from the mantle & is responsible for every type of tectonic hazard. Don’t forget to mention these every time you explain the formation of tectonic hazards.

Distribution of Tectonic Hazards

Plate Margins

Constructive – move apart Destructive – move together

Collision – collide together Conservative – move alongside

Which Hazards are found at Plate Margins

Volcanoes Earthquakes

• Constructive margins – Hot magma rises between the plates as they move apart. The magma erupts as fluid lava – cools and builds up in layers to create the gentle slopes of a shield volcano e.g.. Iceland.

• Destructive margins – a heavier oceanic plate subducts under a continental plate. Friction causes the oceanic plate to melt in the mantle and pressure forces viscous magma upwards . Eruptions of lava and ash build up in layers once cooled to form the steep slopes of a composite volcanoes e.g. Andes Mountains

• Destructive margins –pressure builds between the subducting oceanic plate and the continental plate. This is released in a sudden jerking movement as shockwaves which travel from the focus to the epicentre directly above.

• Conservative margins – plates slide past (parallel to) each other. They get stuck and pressure builds it is released at the focus below the ground as shockwaves and travels upwards to the epicentre on the surface. E.g. Christchurch Quake New Zealand.

• Collision margins – 2 continental plates move towards each other (same weight). They buckle upwards to form fold mountains (Himalayas) as they move they get stuck - pressure builds and is released as shockwaves at the...

Convection currents in the mantle start

to move the plates apart.

Magma rises and fills the gap between

the 2 plates.

The magma erupts as fluid (runny &

thin) lava and cools. This builds up in

layers over time to form the gentle

slopes of a shield volcano.

FORMATION OF EARTHQUAKES AT CONSERVATIVE MARGINS

FORMATION OF VOLCANOES AT CONSTRUCTIVE MARGINS

FORMATION OF VOLCANOES & EARTHQUAKES AT DESTRUCVTIVE MARGINS

Convection currents in the mantle

move heavier oceanic plates into and

under (subducting) lighter continental

plates.

The subducting oceanic plate melts

into the mantle creating lots of heat.

Magma rises through weaknesses in

the rock.

Violent eruptions of ash and viscous

lava. Often due to earthquakes as the

plates slip past each other. Ash and

lava builds up in layers to form steep

slopes of composite volcanoes.

Monitoring Prediction

Seismometers measure earth movement. that may be foreshocks for quakes.

Volcanoes give off gases e.g. Sulphur dioxide that can be recorded.

By observing monitoring data, this can allow evacuation before event in a

volcano. In Earthquakes this is tricky – Seismic Gap

theory is unreliable.

Protection Planning

Reinforced buildings and making building foundations that absorb movement.

Pyramid shaped builds have a low centre of gravity and are much more stable. E.g.

Sky Tower New Zealand. Automatic shut offs for gas and

electricity to prevent fires.

Avoid building in at risk areas Training for emergency services and

planned evacuation routes and drills e.g. Shake Out Day October 15th New Zealand so that people know what to do. E.g. Drop

– Cover – Hold.

Effects of Tectonic Hazards

Primary effects happen immediately. Secondary effects happen as a result of the primary effects and are therefore often slightly later.

Primary - Earthquakes Secondary - Earthquakes

• Property and buildings destroyed • People injured or killed • Ports, roads, railways damaged • Pipes (water and gas) and electricity

cables broken

• Business reduced as money spent repairing property

• Blocked transport hinders emergency services

• Broken gas pipes cause fire • Broken water pipes lead to a lack of

fresh water

Primary - Volcanoes Secondary - Volcanoes

• Property and farm land destroyed • People and animals killed or injured • Air travel halted due to volcanic ash • Water supplies contaminated

• Economy slows down. Emergency services struggle to arrive

• Possible flooding if ice melts Tourism can increase as people come to watch

• Ash breaks down leading to fertile farm land

Comparing Earthquakes – Christchurch New Zealand (HIC) and Ghorka, Nepal (LIC)

Christchurch, Feb. 2011 6.3 magnitude

Nepal ,April 2015 7.8 magnitude

Primary Effects

-185 killed (95 during quake) -6,800 people injured -A TV station collapses and catches fire killing over 90 people. -80% of city has no power.

-8,800 killed & 22,000 injured -Avalanche on Everest kills 19 tourists -World heritage sites e.g. Durbar square flattened. This is a major tourist destination.

Secondary Effects

-Rugby World Cup games are moved to another city causing further loss of income e.g. from tourism. -A fire in a TV station kills 90 people.

-Malnutrition on increase within 3 months. -450,000 homeless & threat of hypothermia for people living in tents in winter. 15,000 living tents in Himalayan village of Barpak. -Concerns that diseases e.g. cholera will spread with dirty drinking water. -Tourist income is down (6% of GDP).

Immediate Responses

-Specialist search and rescue teams are on scene within minutes. -Chemical toilets were provided for 30,000 residents -The final survivor is pulled from the rubble the following day. -Australia sends $6 million worth of aid to help New Zealand. -Mobile homes are provided for 1000s of homeless.

-Difficult to get to people due to strong aftershocks -Relatives search through rubble with bare hands. -People in isolated mountain villages cannot be reached for days or weeks. -Nepal’s army help in cities first. -$81million in aid e.g. blankets, tents & medical supplies sent from UK.

Long term responses

-People are angry that the damaged cathedral is to be demolished & rebuilt -$4o billion to rebuild Christchurch.

10,000+ still living in tents in Himalayas (5 months later) -US army sends helicopters to drop emergency food & shelter to people cut off in Himalayan mountains (weeks later).

LICs suffer more than HICs from natural disasters because they are not as prepared and struggle to react effectively & swiftly.

Measuring Earthquakes

Tectonic Hazards - Earthquakes Why Do People Live in Areas at Risk of Tectonic Hazards?

• Earthquakes and volcanoes do not happen very often so are not seen as a great threat in most people’s lives.

• Better building design can withstand earthquakes so people feel less at risk. • More effective monitoring of volcanoes and tsunami waves enable people to receive

warnings and evacuate before events happen. • People living in poverty have other things to worry about on a daily basis e.g. Money,

food, shelter etc. • Plate margins are often found in areas which are favourable for settlement e.g.

Coasts where ports are developed for trade and tourism. • Some people are not aware of the risks that exist. • Volcanoes can bring benefits such as fertile soil, for farming, rock for building and

rich mineral deposits. • Geothermal energy can be taken from hot water e.g. In Iceland over 90% of all

energy for heating comes from geothermal heat.

Responses to Tectonic Hazards

Immediate (short term) Long-term

• Issue warnings if possible • Rescue teams search for survivors • Treat injured • Provide food and shelter, food and

drink • Recover bodies • Extinguish fires

• Repair and re-build properties and infrastructure

• Improve building regulations • Restore utilities • Resettle locals elsewhere • Develop opportunities for recovery

of economy • Install monitoring technology

Global atmospheric circulation

At the equator, the sun’s rays are most concentrated. This means it is hotter. This one fact causes global atmospheric circulation at different latitudes.

High pressure = sinking air (no clouds) so dry climates & weather. Low pressure = rising air (clouds) so wet climates and weather.

Tropical Storms

• Occur in low latitudes between 5 and 30 degrees north and south of equator. • Ocean temperature needs to be above 27 degrees C. • Hurricane season is between summer and autumn when seas are at their hottest in the Northern Hemisphere. • All tropical storms blow from East to West (impacting the East Coast of continents) with the trade winds. •They spin due to the rotation of the Earth.

Typhoon Haiyan, Philippines, Nov. 2013, Category 5, 175 mph winds.

Primary Effects Secondary Effects

-6300 killed (most drowned by 15 metre storm). -600,000 displaced & 40,000 homes gone. -90% of Tacloban City destroyed. -Widespread flooding. -Tacloban airport badly damaged -300,000 fishing boats destroyed

-14 million affected in total -6 million lost their source of income. -Flooding causes mudslides blocking roads. -Power supplies down for a month. -Shortages of water, food & shelter led to diseases such as cholera. -Looting & violence broke out in Tacloban

Immediate Responses Long-term Responses

-US aircraft carrier George Washington assisted with search & rescue. -1200 evacuation centres set up. -Red Cross delivered basic food aid e.g. rice, canned food & cooking oil. -Shelter kits sent e.g. first aid, water containers, mosquito nets, waterproofs & blankets

-Rebuilding of roads, bridges & airports. -‘Cash for work’ programmes – people paid to clear debris & rebuild Tacloban. -Charities such as Oxfam supported the replacement of fishing boats (a vital source of income). -1000s of homes rebuilt away from areas at risk from flooding. -More cyclone shelters built.

Sequence of a Tropical Storm

1. Air is heated above warm tropical oceans. 2. Air rises under low pressure conditions causing mass evaporation. 3. Strong winds form as rising air draws in more air and moisture causing torrential

rain. 4. Air spins anticlockwise around a calm eye (centre) of the storm. 5. Cold air sinks in the eye so it is clear and dry. 6. Heat is given off as it cools powering the storm. 7. Storm surges (high waves) hit coastal regions causing flooding. 8. On meeting land, they lose power due to friction & reduced moisture. 9. They reach cooler latitudes as they move away from the tropics and lose power.

Extreme weather in the UK

Torrential or Prolonged Rain – can cause flooding damaging homes and business Blizzards of Snow & Ice – cause injuries and disruption to schools and business. Destroy farm crops Drought – limited water supply . Can damage crops Strong Winds – damage to property and damage to trees potentially leading to injury Heat waves – causes breathing difficulties and can disrupt travel.

UK weather is getting more extreme due to climate change. Temperatures are more extreme and rain is more frequent and intense leading to more flooding events. Since 1980 average temperature has increased 1 degree and winter rainfall has increased.

Prediction Planning Protection

-Thermal satellite images track the strength & predict the path of the storm. -Forecasts can predict when storms are likely and expected in an area. -Forecasting allows people to plan immediate actions

-Windows, doors & roofs reinforced to strengthen buildings. -Storm drains to take away rainfall & prevent floods. -Sea walls built to protect key areas v. storm surges. -Houses close to coast constructed on stilts. -1000s of storm shelters constructed.

-Educating people on the dangers of tropical storms. -Evacuation of areas most at risk (easier in HICs) -Board up windows to stop them smashing -Wear a motorbike helmet in case of flying objects. -Get to higher land

Somerset Levels Floods - December 2013 to February 2014 - UK

Natural Causes: Wettest January on record. -350mm of rain (100mm above av.). -High tides and storm surges up the Bristol Channel. -The confluence of many rivers e.g. Parratt and Tone on low lying flood plain.

Human Causes: The rivers had not been dredged of sediment for at least 20 years reducing the capacity of river channels. -Human settlement and farming developments on an area prone to annual flooding

Social Effects

-Over 600 houses flooded & villages e.g. Moorland cut off. This affected daily lives e.g. school attendance, shopping etc. -Residents evacuated to temporary accommodation. -Power supplies cut off.

Economic Effects

-Cost to Somerset County Council of £10 million. -14,000 hectares of farm land under water for a month & 1000 livestock evacuated. -Bristol to Taunton rail line closed to Bridgewater & Road closures impact ability for travel to work.

Environmental impacts

-Floodwaters heavily contaminated with sewage and pollutants & debris. -Stagnant water collected over months could not be pumped back into rivers until it had been re-oxygenated.

Management strategies

Immediate: -Sand bags put around properties in response to flood alerts. -people moved valuables upstairs. -villagers used boats to get in and out & take kids to school or visit shops. -local community groups and volunteers helped others in need – especially the elderly.

Long Term: -20 million Flood Action Plan launched by Council & Environment Agency. -March 2014 - 8km of Rivers were dredged to increase capacity of channels. -Road levels raised to enable access & business to continue in future floods. -River banks raised and more pumping stations built.

Climate change will affect tropical storms too. Warmer oceans will lead to more intense storms – but not necessarily more frequent ones

Climatic Hazards

Climate Change – natural or human?

Evidence for climate change shows changes before humans were on the planet. So some of it must be natural. However, the rate of change since the 1970s is

unprecedented. Humans are responsible – despite what Mr Trump says!

Causes

Natural Human

• Orbital changes – The sun’s energy on the Earth’s surface changes as the Earth’s orbit is elliptical every 100,000 years. (rotates like a rugby ball rather than a football!)

• Solar Output – sunspots increase to a maximum every 11 years

• Volcanic activity – volcanic activity reflects sunlight away reducing global temperatures temporarily

• Fossil fuels – release carbon dioxide with accounts for 50% of greenhouse gases

• Agriculture – accounts for around 20% of greenhouse gases due to methane production from cows etc. Larger populations and growing demand for meat and rice increase contribution

• Deforestation – logging and clearing land for agriculture increases carbon dioxide in the atmosphere and reduces ability to planet to absorb carbon through photosynthesis.

• Waste –landfill (methane) & sewage treatment (Nitrous Oxide) release GHGs

• Transport – CO2 emissions from transport burning fossil fuels e.g. Cars and planes.

Evidence for Climate Change

The Met Office has reliable climate evidence since 1914 – but we can tell what happened before that using several methods.

Ice and Sediment Cores Tree Rings

• Ice sheets are made up of layers of snow – one per year. If you drill down you can analyse gases trapped in layers of ice for the past. Ice cores from Antarctica show changes over the last

400 000 years. • Remains of organisms found in cores

from the ocean floor can by traced back 5 million years.

• A tree grows one new ring each year. Rings are thicker in warm, wet conditions

• This gives us reliable evidence for the last 10 000 years

Pollen Analysis Temperature Records

• Pollen is preserved in sediment. Different species need different climatic conditions

• Historical records date back to the 1850s. Historical records also tell us about harvest and weather reports.

Managing Climate Change

Mitigation Adaption

• Alternative energy production – such as solar power and biomass. Renewable sources will last longer but they can be expensive.

• Planting Trees – helps to remove carbon dioxide. Has the potential to increase carbon storage by 28%. However land may be limited and biodiversity is still threatened unless a wide range of trees are planted

• Carbon Capture – takes carbon dioxide from the emission sources and stores it underground under a cap rock. It can reduce capture of up to 90% of carbon dioxide. However, it is very expensive and unclear if the captured carbon would escape in the long term. Also it discourages development of renewable energy resources

• International Agreements – targets will only be met if they are legally binding (Paris 2015). Financial support is needed for LICs. However, poorer countries argue that they need to industrialise and getting richer countries to accept their responsibility is difficult.

• Changes in agricultural systems – needed to react to changing rainfall and temperature patterns and changing threat of disease and pests. This is hard for poor farmers who tend to be most affected

• Managing water supplies – In Ladakh India locals are creating artificial glaciers that will supply local villages. Water is collected in winter through a system of diversion canals and embankments and it freezes. When the glacier melts in spring it will provide vital fresh water for local villages.

• Reducing risk – 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. These are expensive and possibly only short term measures.

Effects of Climate Change

Socio - Economic Environmental

• Increased disease eg. skin cancer and heat stroke

• Winter deaths decrease with milder winters

• Crop yields affected by up to 12% in South America but will increase in Northern Europe (but will need more irrigation).

• Less ice in Arctic Ocean increases shipping and extraction of oil and gas reserves

• Droughts reduce food and water supply in sub-Saharan Africa.

• Water scarcity in South and South East UK

• Increased flood risk. 70% of Asia is at risk of increased flooding

• Millions of refugees from countries close to sea level e.g. Bangladesh.

• Skiing industry in Alps threatened.

• Increased drought in Mediterranean region

• Increased intensity and frequency of tropical storms.

• Increasing floods • Sea level rise leads to flooding and

coastal erosion • Ice melts threaten habitats of polar

bears & polar creatures. • Glacier melt reduces fresh water

supplies to rivers. • Forests in America may experience

more pests, disease and forest fires • Coral bleaching and decline in

biodiversity such as the Great Barrier Reef (Australia)

The Greenhouse Effect.