AS Level Geography - World at Risk (Unit 1: Topic 1)

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Global Hazards

There are Different Types of Hazard

A hazard is something that is a potential threat to human life or property

They are caused by natural processes

1 - Hydro-meteorological hazards are caused by climatic processes e.g. floods + droughts

2 - Geophysical hazards are caused by land processes e.g. earthquakes + landslides

Disaster - When a hazard actually affects humans

Risk - Likelihood that humans will be affected

Vulnerability - Susceptibility of a population (damage)

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Global Hazards Continued...

The Disaster Risk Equation Gives the Risk of a Disaster Occurring


Risk of the disaster increases when the frequency or severity of hazards rise, the vulnerability rises and when the people's capacity to cope is decreased

Global Warming is Arguably the Greatest Current Global Hazard

 - It describes the recent rise in avg global temperature

 - It is a type of climate change

 - There is a belief that global warming is caused by humans

 - It's a CONTEXT HAZARD (scale is global and can set off other hazards/ make them worse)

 - It's a chronic hazard (constant threat + there isn't a quick or easy solution to it)

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Global Hazards Continued...

Hydro-meteorological Hazards are Becoming more Frequent

 - The number of geophysical hazards however has not changed much at all

 - Thought that the increase in number of hydro-meteorological hazards is because of the effects of global warming

Human Factors:                                                       Physical Factors:

Rapid population growth/urbanisation                                 Global warming

Increasing world poverty                                                        El Nino occurrences (unpredicable)

Exploitation of resources

Greater media coverage (seems like more are happening)

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Global Hazards Continued...

Deaths are Decreasing but Economic Losses are Increasing

Prediction - Improved technology enables us to predict when hazards are going to occur so people can be evacuated and property can be secured

Prevention - Prevent natural hazards from turning into disasters e.g. sandbags for floods

Preparedness - Education e.g. Japan has a 'disaster preparedness day' per year

Actual financial cost - Greates in richer countries

Relative financial cost - Greates in poorer countries

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Hazard Distribution

Geophysical Hazards Usually Occur Near Plate Boundaries

 - Earth's crust is made up of plates called tectonic plates which are situated on top of the mantle

 - Two types of crust -> Continental (thicker but less dense + majority is above sea level)-> Oceanic crust (thinner but more dense + majority is below sea level)

 - Plates move due to convection currents in the mantle (caused by temperature differences)

Volcanoes and Earthquakes Occur at Constructive Boundaries

- Constructive boundary is where 2 plates are moving <-->

 - Pressure released when plates move and causes the mantle to melt, creating magma

 - Example of this is the Eurasion plate and N.A. plate are moving apart at the mid-Atlantic ridge -> Iceland formed where the magma has risen

 - Some parts move quicker than others which causes pressure build up and when this becomes too much the plate cracks, creating a fault line which then causes an earthquake (more earthquakes can occur along the fault line) e.g. the San Andreas Fault

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Hazard Distribution Continued...

Volcanoes and Earthquakes Also Occur at Destructive Boundaries

- A destructive boundary appears when 2 plates are moving -> <-

- Continental crust + oceanic crust move towards each other and this forces the more dense oceanic crust under the less dense continental crust (subducted)

 - Oceanic crust is heated by friction and contact with the upper mantle which then causes it to melt into magma

 - Magma will go back up to the surface to create volcanoes

 - Plates can become stuck and this again causes pressure to build up and the plates jerk past each when the pressure is too strong which causes an earthquake to occur

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Hazard Distribution Continued...

Earthquakes also Occur at Conservative Boundaries

- A conservative boundary appears where 2 plates are moving past each other

 - They become locked together and pressure again builds up which causes them to jerk past each other / or to crack forming fault lines, causing an earthquake

 - e.g. Pacific plate is moving past the North American plate and lots of earthquakes appear across this boundary and at the fault lines

Some Volcanoes Occur away from Plate Boundaries

- Examples of this are in Hawaii and the volcanoes are believed to be a cause of magma rising from a big chamber under the crust (places like Hawaii are volcanic hotspots)

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Hazard Distribution Continued...

Tropical Cyclones Occur over Warm Water

- They are massive storms with very strong winds and torrential rain

 - Form above sea water which is 26.5 degrees Celsius or higher

 - Lose strength when moving over land as the energy supply is cut off

 - Appear between 5 and 30 degrees north and south of the equator

 - Coriolis effect causes them to spin

 - Don't form 0-5 degrees either side of the equator (coriolis effect not powerful enough)

 - Also referred to as hurricanes and typhoons

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Disaster Hotspot Case Study - California

California is a Disaster Hotspot

- Disaster hotspots are vulnerable places at risk from 2 or more hazards

 - California has lots of highly populated towns and cities at risk from several different hazards

Earthquakes are hazard number 1 - California has 2 or 3 earthquakes each year that have the power to hurt structures and in the past there was a San Francisco earthquake in 1906 that destroyed the majority of the city

Droughts are hazard number 2 - Can be caused by anticyclones, La Nina events and increased wind from desert areas and the worst effect of drought is wildfires (wildfires in Southern California in October 2007 killed 22 people and destroyed 1300 homes)

Tsunamis are hazard number 3 - Series of large waves which can flood coastal areas and they are caused by earthquakes + landslides -> Earthquakes under the Pacific Ocean could lead to a tsunami across the California coastline (Earthquake off the coast of Alaska in 1964 caused a tsunami to hit the coast and it killed 12 people in Crescent City)

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Disaster Hotspot Case Study - California Continued

Hazard number 4 are landslides - They occur on steep, unstable land and the risk is very high because of building on and around steep slopes and on coastal land e.g. La Conchita

Hazard number 5 are volcanoes - There hasn't been an eruption since 1915 (Lassen Peak) but it is being monitored for potential eruptions e.g. Mount Shasta

California is Wealthy but Parts of the Population are Vulnerable

- Over 70% live within 50km of a fault line

 - Lots of buildings on unstable land

 - Many buildings along the coast which are vulnerable to tsunamis

 - 20% in LA live below the poverty line

 - Big economy = BIG ECONOMIC LOSSES

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Disaster Hotspot Case Study - The Phillipines

- Group of islands in south-east Asia

Volcanoes are hazard number 1 - Near to a destructive plate boundary and the islands were formed by both folding at the boundary and by volcanoes forming from risen magma -> Mount Pinatubo, 1991 (many people evacuated, buildings collapsed, crops destroyed etc)

Earthquakes are hazard number 2 - Philippine plate and Eurasian plate become locked (plates jerk when pressure is too much) and earthquakes happen at fault lines -> 1990, 7.8 on Luzon iland which killed 1500+ people

Landslides are hazard number 3 - Get lots of rain which trigger landslides (earthquakes too) -> Leyte island, 2006 a whole village was buried which killed hundreds

Typhoons are hazard number 4 - 10 per year (developing in the Pacific Ocean and moving westwards over the islands) -> Xangsane swept across Manila + densely populated area in the North, 2006

Tsunamis are hazard number 5 - Earthquakes in oceans could cause a tsunami -> 1976 earthquake of 7.9 caused tsunami which struck the coastline around Moro Gulf, Mindanao

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Disaster Hotspot CS - The Philippines Continued...

Droughts are hazard number 6 - Parts have wet and dry seasons like Manila and drought can happen when the wet season hasn't provided sufficient rain to the last dry season/dry season is very harsh -> Luzon island, 2005 power supply reduced (due to decrease in water flow)

Flooding is hazard number 7 - Can be caused by typhoons or heavy rain -> Big floods happened in the lowland areas near Manila during the 70s + in recent years (crops ruined)

Population is Vulnerable

- When a hazard hits a heavily populated area, there is a bigger risk of it becoming a disaster

 - The pressure from the population has caused deforestation (landslides)

 - Fast growing settlements have been built near to hazardous zones

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Evidence for Climate Change

Long-term Climate Change

- Taking temperature is an indicator of climate (huge changes), looking at detailed data from the last 400,000 years shows more detailed fluctuations and climate changed from cold glacial periods (100,000) to warmer interglacial periods (10,000 years)

Medium-term Climate Change

 - Last glacial period was 18,000 years ago, warming was fast after this but not constant and around 5000 years ago, temperatures were 1-2 degrees higher than now

Short-term Climate Change

 - Big rise in temperature over the last 1000 years, general increase but pattern not constant and temps rose steadily from early 20th century until 1940s and then dropped again -> temps have risen sharply again since the 70s

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Evidence for Climate Change Continued...

Long-term Change

- Ice Cores - Sheets made up of layers with one being formed every year -> Gases

 - Pollen Analysis - Pollen preserved in sediment -> Dated -> Can see if conditions are similar

 - Sea Level Change - Ice -> Raised beaches (can be dated) + show less water stored as ice

Medium-term Change

- Historical records - Indirectly indicate different conditions in the past

 - Tree rings - A new tree ring is created every year as a tree grows and if the conditions are good it will produce a thicker ring -> Rings are counted to find the age of a tree and the thickness of every ring indicates  the climate of every year

 - Retreating glaciers - Position of rocks deposited shows how big a glacier was and how far it extended -> Distance of rocks from the current glacier indicates climate change

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Evidence for Climate Change Continued...

Short-term Change

- Weather records - Information about weather conditions have been gathered since 1861 -> Show climate changes

 - Polar Ice Melt - Reduction in ice at both poles and this implies there have been changes in climatic factors

 - Ecosystem Changes - Temperature alterations have an impact on the availability of food and shelter which has an impact on what species live there

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Causes of Climate Change

Natural Causes

1 - Variations in the Earth's orbit -> Stretch (path of orbit changes to an ellipse and back which affects the distance from the Sun and hence the amount of energy it receives too), tilt (earth tilted at an angle which changes the amount of energy which latitudes receive) and wobble (wobbles in a circle and different hemispheres receive different temperatures)

2 - Variations in solar output -> Sunspots (increase solar energy output) increase and decrease in amount in an 11 year cycle

3 - Meteor impacts -> Creates a crater and release big amounts of material into the atmosphere which can lead to sunlight being blocked out, changing the climate

4 - Volcanic eruptions -> Release big amounts of material into the atmosphere which can also block out sunlight, changing the climate

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Causes of Climate Change Continued...

Human Causes

1 - Enhanced Greenhouse Gas Emissions- Since industrial revolution in the mid-19th century levels of atmospheric CO2 have increased and this has caused an increase in temperature

2 - Destruction of Natural CO2 Sinks - CO2 is released when trees are burnt by forest fires or to make way for agriculture -> Believed that many greenhouse gas emissions from humans could be stored in CO2 sinks and now it is believed that they won't be able to cope and more CO2 will enter the atmosphere

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Impacts of Climate Change

Global Warming is Causing Ice to Melt

- Melting of ice means water returns to the oceans which causes sea level to rise (eustatic)

 - Higher global temperatures mean that oceans become warmer + expand (thermal expansion) and this leads to the volume of water to rise which then causes sea levels to rise by even more


- Bangladesh -> 80% low-lying land and if sea level rises then it will submerge a majority of it which would have an impact on many people as Bangladesh has a high population density and the situation would be worse as it is a poor country

- The Maldives -> Low-lying set of islands in the Indian Ocean and if sea level rises by 0.5m the majority of the country would be submerged but the population isn't poor (however the economy is dependent on tourism)

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Impacts of Climate Change Continued...

Global Warming is Causing Permafrost to Thaw

- Permafrost is gournd which has been permanently frozen for 2 or more years and it covers roughly 20% of Earth's surface

 - These areas of permafrost are natural CO2 sinks and it is stored as organic material within the soil and the thawing of the permafrost exerts some of this -> Thawing leads to the collapse of buildings and pipelines built on it but it can offer economic benefits for humans

Causing other Changes in Climate too

- Increase in regularity of extreme weather events

 - Change in distribution of climatic regions which affects ecology, agriculture but it can bring benefits to certain human activities e.g. tourism

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Impacts of Climate Change Continued...

Emissions Scenarios (I will Come back to this another time)

- Difficult to predict impacts of changes in climate as there is uncertainty:

 - Don't know how emissions will alter and we don't know how much of the emissions will be absorbed by natural CO2 sinks etc.

 - Extent of climate change due to natural causes is unknown

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Impacts of Climate Change

Tipping Point

- Little rise in temperature would lead to catastrophic and irreversible changes to the environment, forming a much more hazardous world

 - This could be caused by a change in the climate speeded up by the impacts which have been already caused

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Climate Change - Case Studies


Background Information: 

- Area of Arctic sea ice has been shrinking at an increasing rate

 - Greenland ice sheet is melting

 - Permafrost area is shrinking

 - Treeline is moving North + area where trees can't grow is shrinking


- ENVIRONMENTAL - Fresh water into sea (melting of ice sheets) + thawing of permafrost releases more CO2 and methane

 - ECOLOGICAL - Changing climatic regions means habitats are being reduced/lost, sensitive ecosystems

 - SOCIO-ECONOMIC - Shrinking sea ice could open up new shipping routes, new natural resources (can lead to conflict over who owns them), thawing of permafrost can cause buildings and broken pipelines to collapse

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Climate Change - Case Studies Continued...

Arctic Warming's Consequences on the Rest of the World

- Melting of ice sheets will add to rising global sea levels

 - Ocean currents in the Arctic are affected by salinity changes which has an impact on global ocean currents as they work as an interlinked system

 - Changing temps, sea ice and landscapes affect air currents in the Arctic which affects global weather patterns (atmosphere - interlinked system)

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Climate Change - Case Studies Continued...


Background Information:

- Areas which are already dry are becoming drier

 - Wetter areas are becoming wetter

 - Whole of the continent is becoming warmer (0.5 degrees in the last century)

 - Poor people have a reduced capacity to cope and poorer countries are less able to prepare for and respond to the impacts of climate changes

 - Political turmoil means that appropriate responses aren't made which makes the impacts of climate change even worse

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Climate Change - Case Studies Continued...

Africa Continued...

Examples of Impacts:

- DESERTIFICATION - Big issue in the Sahel region and it leads to decrease in agricultural production causing more poverty, unemployment, malnourishment and starvation


 - REDUCED GROWING PERIOD OVER MAJORITY OF CONTINENT - Decreases agricultural production (70% of employment in Sahel region)

Africa have contributed little to the causes of global warming but are suffering the most

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Coping with Climate Change

Mitigation Strategies to Cope with Climate Change:

- Carbon Tax - Discourage overconsumption of energy

 - Energy conservation - Using less energy

 - Tree planting - Produces new carbon sinks

 - Waste strategies - Increase quantity of waste recycled which should cut methane emissions from landfill sites

Adaptation Strategies to Cope with Climate Change:

- Lifestyle adaptations - e.g. planting new crops which will flourish in the new climatic conditions

 - Water resource management - Utilising freshwater resources more efficiently to cope with drought conditions

 - Community awareness - Education on likely impacts of CC -> Emergency action plans

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Coping with Climate Change Continued...

Strategies tend to have Limitations + Side Effects

Limitation - e.g. flood defences works until they aren't high enough to cope with higher flood waters

Side effect - e.g. changing energy mix would reduce emissions but using more nuclear power would create nuclear waste (expensive and dangerous to get rid of)

Key Players with Different Roles (Agreeing on how to Cope with CC):

- Governments - Develop strategies on an international, national and local scale

 - Businesses - Can be responsible for worsening CC or can help to slow it down

 - Non-governmental organisations (NGOs) - Can have lots of roles and views depending on what they're set up to do and who their members are

- Communities and individuals - Strategies developed on a larger scale are done locally

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Coping with Climate Change Continued...

The Kyoto Protocol:

- International agreement between more than 180 countries to monitor and cut greenhouse gas emissions by 2012

 - Divided countries into 2 groups; developed and developing

 - Developed countries agreed to cut emissions (overall by 5%)

 - They had to monitor and report their emissions

 - Carbon 'credits' were used

Individuals can 'Act Local, Think Global'

- Individuals can make small changes which will help global problem e.g. reduce carbon footprint

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