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The Challenge of Natural Hazards - Coggle Diagram
The Challenge of Natural Hazards
Natural Hazards
Main Types of Natural Hazards
Geological Hazards
caused by land and tectonic processes
e.g.
volcanoes
,
earthquakes
,
landslides
and
avalanches
Meteorological Hazards
caused by weather and climate
e.g.
tropical storms
,
heatwaves
and
cold spells
Factors that affect Hazard Risk
Vulnerability
the more people that are in an area exposed to natural hazards the greater the probability they will be affected by a natural hazard
Capacity to Cope
the better a population can cope with an extreme event = the lower the hazard risk
e.g. HICs are able to cope with flooding because they can afford to build flood defences
Nature of Natural Hazards
Type
the risk from some hazards is greater than others
e.g. tropical storms can be predicted and monitored, giving people time to evacuate
whilst earthquakes happen sporadically, making it harder to protect people
Frequency
natural hazards that occur more often may carry a higher risk
Magnitude
more severe natural hazards that occur more often may carry a higher risk
hazard risk - probability of people being affected by a hazard in a particular area
a natural process which could cause death, injury or disruption to humans or destroy possessions
A natural disaster is a natural hazard that has actually happened and affected people
Extreme events which don't pose any threat to human activities are not counted as hazards
Effects And Responses
Effects
Primary
buildings and roads are destroyed by earthquakes, volcanic eruptions or tropical storms
People are injured or killed
Crops and water supplies can be damaged or contaminated
infrastructure can be damaged, cutting off supplies (e.g. gas pipes)
Secondary
hazard can trigger other hazards (e.g. earthquakes cause tsunamis)
Aid and emergency vehicles can't get through because of blocked roads or bridges
shortage of clean water makes it easier for diseases to spread
food shortages can occur if crops are damaged
country's economy can be weakened - damage to businesses can cause unemployment, and the reconstruction process can be very expensive
Responses
Immediate
evacuate people
treat the injured and rescue anyone cut off by damage to road or bridges
provide temporary supplies of electricity and gas if regular ones have been damaged
provide food, drink and shelter to people w/o homes
foreign governments or charities may send aid workers, supplies or financial donations
Long-Term
repair homes or rehouse people who have lost their homes
repair or rebuild buildings, roads, railways and bridges
reconnect broken infrastructure (e.g. gas pipes)
improve forecasting, monitoring and evacuation plans
improve building regulations so that buildings can withstand similar hazards in the future
boost economic recovery (e.g. by promoting tourism)
Tectonic
Hazards
Types of Plate Margins
Destructive
where two plates move towards each other
where the oceanic plate meets a continental plate, the denser oceanic plate subducts under the continental plate and destroyed - which creates gas-rich magma
Volcanoes and ocean trenches occur here
where two continental plates meet, the ground is folded upwards, creating fold mountains
Constructive
where two plates move away from each other
magma rises from the mantle to fill the gap and cools, creating new crust
Conservative
where two plates move sideways past each other or are moving in the same direction but at different speeds
crust isn't created nor destroyed
Earth's Surface
the earth's crust is divided into slabs called tectonic plates that float on the mantle
Types of Crust
Continental
thicker (30-50km)
less dense
Oceanic
thinner (5-10km)
more dense
the plates move due to convection currents in the mantle
the places where plates meet are called plate margins/plate boundaries
Volcanoes and Earthquakes
Volcanoes
only occur at destructive and constructive plate margins
at destructive margins, the denser oceanic plate subducts into the mantle and melts
a pool of magma forms, which then rises through cracks of the crust
the magma then erupts, forming a volcano
at constructive margins, the magma rises up into the gap created by plates moving apart, forming a volcano
Earthquakes
occur at all three types of plate margins
at destructive plate margins, tension builds when one plate gets stuck as it moves past the other
at constructive margins, tension builds along the cracks in the plates as they move away from each other
at conservative margins, tension builds up when plates that are grinding past each other get stuck
Why do people live in high risk areas?
they may not be able to afford to move
people may not know the risks
they've always lived there - moving means leaving their jobs and/or families
in wealthier countries, effective monitoring and evacuation plans can minimise risks
they're confident that their government will support them after an earthquake or volcanic eruption
minerals from volcanic ash are very fertile - which attracts farmers
volcanoes are tourist attractions, so lots of people live nearby to work in the tourist industry
Management
Monitoring
seisometers and lasers monitor earth movements and can be used in early warning systems to give a small but vital amount of warning
scientists can monitor tell-tale signs that come before a volcanic eruption, such as tiny earthquakes, escaping gas, and changes in the shape of a volcano
Prediction
earthquakes cannot be reliably predicted but scientists can forecast where they occur via monitoring the movement of tectonic plates
volcanic eruptions can be predicted if scientists monitor volcanoes closely
Planning
future developments can avoid high-risk areas
emergency services can prepare by practising rescuing people for example
people can be educated so that they know what to do in the event of a hazard
governments can plan evacuation routes to get people away quickly and safely
emergency supplies such as blankets, clean water and food can be stockpiled
Protection
new buildings can use reinforced concrete that absorb an earthquake's energy
existing buildings can be strengthened with steel frames so they're less likely to collapse
buildings can be strengthened so that they're less likely to collapse under the weight of ash
trenches and barriers have been used to try and divert lava away from settlements, but with little success
Weather
Hazards
Global Atmospheric Circulation
the transfer of heat from the equator to the poles by the movement of air
air moves due to differences in air pressure - winds blow from high pressure areas to low pressure areas
the GAC system is divided into loops (cells) - each cell has warm rising air that creates a low pressure belt and cool sinking air that creates a high pressure belt
The sun warms the Earth at the equator, causing the air to rise - which creates a low pressure belt
as the air rises it cools and moves away from the equator
30° n/s of the equator, the cool air sinks, creating a high pressure belt
at the ground surface, the cool air moves either back to the equator as trade winds or towards the poles as westerlies
these winds curve due to the Earth's rotation - this is called the Coriolis effect
60° n/s of the equator the warmer surface winds meet colder air from the poles
the warmer air rises, creating low pressure
some of the air moves back towards the equator, and the rest moves towards the poles
at the poles the cool air sinks, creating high pressure air is then drawn back towards the equator
GAC influences weather and climate
at the equator, the sun is directly overhead - which means it receives a lot of solar radiation so it's hot
warm, moist air rises and forms clouds, so it rains a lot
By the time air reaches 30° n/s of the equator, it has released most of its moisture as rain
dry air means there are few clouds and little rainfall so deserts are often found at this latitude
The UK likes close to the low pressure zone at 60° north
warm rising air brings lots of cloud cover and rainfall, often as low pressure systems carried from the Atlantic by westerly winds
Tropical Storms
hurricanes, typhoons and cyclones
develop between 5° and 30° n/s of the equator when:
sea temperature is 27°C or higher
wind shear (difference in wind speed), between higher and lower parts of the atmosphere is low
the warm surface water evaporates, rises and condenses into clouds
this releases huge amounts of energy producing powerful storms
the rising air creates an area of low pressure - which increases surface winds
low wind shear prevents clouds breaking up as they rise, so the storm stays intact
easterly winds near the equator move tropical storms towards the west
the storms spin because of the Coriolis effect
as storms move over oceans, the energy from the warm water strengthens the storm, so wind speeds increase
storms lose strengthen when they move over land or cooler water, because the energy supply from the warm water is cut off
the majority of storms occur in the northern hemisphere from Aug to Oct whilst in the southern hemisphere most storms occur from Dec to Apr
Features
the centre of the storm is called the eye
it's up to 50km across
caused by descending air
there's very low pressure, light winds, no rain, no clouds and a high temperature
the eye is surrounded by the eyewall, where there's spiralling rising air, very strong winds that are around ~160km/h
storm clouds, torrential rain and a low temperature
towards the edges of the storm the wind speed falls, the clouds become smaller and more scattered,the train becomes less intense and the temperature increases
they spin anticlockwise in the northern hemisphere and clockwise in the southern hemisphere
Typhoon Haiyan (2013)
made landfall on the Philippines on 8th November 2013
Tacloban and Cebu were among the worst affected areas with up to 280mm of rain and winds reaching 314km/h
a storm surge with waves of up to 2.3m combined with a high tide, meant that Tacloban was hit by waves of up to 5m
Effects
Primary
8000 people were killed
1 million homes were damaged
1.9 mil people made homeless
damaged infrastructure
contaminated water
Secondary
Flooding triggered several landslides - which blocked roads and delayed the arrival of aid
5.6 million workers lost their jobs after businesses and agricultural land were destroyed
the lack of clean water caused outbreaks of diseases such as dysentery
Responses
Immediate
PAGASA broadcasted warnings about Typhoon Haiyan two days before it made landfall, leading to the evacuation of 800,000 residents before the storm
Fishermen were warned not to go to sea
The Philippines declared a state of emergency which led to many charities offering aid in the form of food, shelter and clean water
Long term
the UN appealed for over $300 million to help fund rebuilding and relief
Charities built new storm-resistant houses
The Philippines' tourism board encouraged people to visit the country after the storm by emphasising that most areas were unaffected and that money from tourism would help with the rebuilding process
Affects of Climate Change
Frequency
Oceans will stay at 27°C or higher for longer each year so there's a longer period when tropical storms can form. This may mean that there are more storms each year
Distribution
As the average ocean temperature rises, more of the world's oceans could be above 27°C - this may mean that tropical storms can form in areas that haven't experienced them before (e.g. at higher latitudes)
Intensity
Higher sea surface temperatures are likely to result in more evaporation and increased cloud formation so more energy is released and therefore, storms could become more powerful
Ways to Reduce the Effects
Prediction & Monitoring
Storms can be monitored using radar, satellites and aircraft. Computer models can then be used to calculate a storm's predicted path
Predicting where and when a tropical storm is going to happen gives people time to evacuate and protect their homes and businesses
e.g. during Typhoon Haiyan, predicting the storm's path helped authorities decide which areas need to be evacuated
Planning
Future developments (e.g. new houses can avoid high-risk areas such as low-lying coastal zones)
Governments can plan evacuation routes to ensure people can get away quickly
Emergency services can prepare for disasters by practising rescuing people from flooded areas
e.g. after Typhoon Haiyan, volunteers started rescue simulations so they were better prepared for future storns
Protection
Buildings can be designed to withstand tropical storms such as being put on stilts so they're safe from floodwater
Flood defences can be built along rivers (e.g. levees) and coasts (e.g. sea walls)
e.g. mangrove forests are being planted in the Philippines to act as a natural flood defence
UK Weather Hazards
Strong Winds
can damage properties and disrupt transport
Heavy Rainfall
can cause flooding and can damage, homes, disrupt transport networks and drown people
Snow and Ice
schools and businesses can be forced to shut, and disruption to travel can have economic impacts
Drought
water supplies can run low, causing economic impacts such as crop failures
Thunderstorms
can cause fires which can damage property and the environment, and can occasionally kill people
Heat waves
Pollution builds in the air - which can cause heat exhaustion and breathing difficulties, which can kill people
Climate Change
Evidence
Ice Cores
Ice sheets are made up of layers of ice - one layer is formed each year
Scientists drill into ice sheets to get long cores of ice
By analysing the gases trapped in the layers of ice, they can tell what the temperature was each year
smaller the concentration of greenhouse gases = less hot the year was
Tree Rings
As a tree grows it forms a new ring each year - the tree rings are thicker in warm, wet conditions
Scientists take cores and count the rings to find the age of a tree. The thickness of each ring shows what the climate was like
Tree rings are a reliable source of evidence of climate change for the past 10,000 years
Pollen Analysis
Pollen from plants gets preserved in sediment
Scientists can identify and date preserved pollen to show which species were living at the time
Scientists know the conditions plants live in now, so preserved pollen from similar plants tells us the climate conditions were similar
Temperature Records
Since the 1850s, global temperatures have been measured accurately using thermometers
this gives a reliable but short term record of temperature change
Historical records like harvest dates or newspapers can extend the record of climate change further back
Causes
Human
Burning Fossil Fuels
CO2 is released into the atmosphere when fossil fuels are burnt
Cement Production
cement is made from limestone - which contains carbon
when cement is produced, lots of CO2 is released into the atmosphere
Farming
Farming livestock produces a lot of methane because of cow farts
Rice paddies contribute to global warming due to flooded fields emitting methane
Deforestation
Plants remove CO2 from the atmosphere and convert it into organic matter via photosynthesis
When trees are cut down, they stop taking in CO2
CO2 is also released into the atmosphere when trees are burnt as fuel or to make way for agriculture
when greenhouse gases absorb outgoing heat from the Earth, reducing the amount of heat lost to space, that is the greenhouse effect
if greenhouse gas levels increase, more energy is trapped and the planet warms up even more
Natural
Orbital Changes
Affects how much solar radiation (energy) the Earth receives - more energy means more warming
There are variations in the way the Earth orbits the Sun:
Stretch - the Earth's orbit around the Sun varies from circular to elliptical (oval-shaped) (eccentricity)
Tilt - the Earth's axis' tilt varies from 22.5° to 24.5° as it orbits the Sun. The greater the tilt, the more extreme the seasons are and the more solar energy the poles receive
Wobble - the Earth's axis wobbles like a spinning top (known as precession) and leads to some regions around the world experiencing more daylight hours at certain times of the year
These changes may have caused the glacial and interglacial cucles of the Quaternary Period
Volcanic Activity
Major volcanic eruptions eject large quantities of material into the atmosphere (ash and sulphur dioxide)
Some of these particles will be spread across the Earth's atmosphere by high level winds if they rise high enough and they will reflect the Sun's rays back into space and so the Earth's surface cools
Volcanic activity may cause short-term changes in climate
(e.g. in 1991, Mount Pinutobu erupted, releasing 17m tonnes of sulphur dioxide - which was enough to reduce the sunlight by 10% and global temperature by 0.5°C/year)
Solar Output
The sun's energy output isn't constant - changes in short cycles of ~11 years
Reduced solar output means that the Earth's climate may become cooler in some areas
Solar output isn't thought to have a major effect on global climate change
Effects
Environment
warmer temperatures cause glaciers to shrink and ice sheets to melt - which means causing sea levels to rise
Sea ice is also shrinking, leading to the loss of polar habitats
Rising sea levels means coastal areas will flood more regularly
Coastal erosion will increase and some coastal areas will be submerged, leading to habitat loss
Other species are declining due to warming (e.g. coral reefs because high temps make coral expel algae, causing them to starve and die)
Precipitation patterns are changing - global warming is affecting how much rain areas get
The distribution and quantity of some species could change and biodiversity could decrease:
Some species now live at higher latitudes due to warming temperatures
Some habitats are being damaged or destroyed because of climate change which may lead to extinction
People
In some places, deaths due to heat have increased - but deaths due to cold have decreased
Some areas could become so hot and dry they're difficult or impossible to inhabit
Some coastal areas could flood so often that they become uninhabitable
may lead to migration and overcrowding in other areas
Some areas are struggling to supply enough water due to problems with water availability caused by changing rainfall patterns
can lead to political tensions
Weather is getting more extreme meaning more money has to be spent on predicting extreme weather events, reducing their impacts and rebuilding after they take place
Globally, crops have suffered from climate change
(e.g. warming in recent years has caused smaller yields in Argentina's wheat crops)
Some farmers in high-latitude countries are finding that their crops benefit from warmer conditions and produce higher yields
Lower crop yields could increase malnutrition, ill health and death from starvation
Managing Climate Change
Mitigation
Planting Trees
Increases the amount of CO2 that's being absorbed from the atmosphere through photosynthesis
Takes a long time for trees to grow and reach their fool potential at absorbing carbon
Carbon Capture
Carbon Capture and Storage is designed to reduce emissions from power stations burning fossil fuels
CCS involves capturing CO2 and transporting it to safe places where it can be stored (e.g. deep underground)
Expensive and encourages the use of fossil fuels
Alternative Energy Production
Replacing fossil fuels with nuclear or renewable energy can help reduce greenhouse gas emissions
In the UK, more offshore wind farms are being built in East Anglia and several wave, tidal and nuclear power projects have been planned
Lots of alternative energy are dependent on weather / won't work in specific condition and aren't versatile to use
International Agreements
The Paris agreement aims to reduce GHG emissions and limit global warming and it has been signed by 195 parties
It encourages developing countries to help developing countries put mitigation strategies into place
It's not legally binding and some countries rely on exporting fossil fuels (e.g. UAE), to make money
reduces the causes of climate change, by reducing the concentration of greenhouse gases in the atmosphere
Adaptation
Changing Agricultural Systems
Crops
Start planting new crop types that are more suited to the new climate conditions in an area (e.g. soya, peaches and grapes may be grown in southern England)
Biotechnology
In some regions, biotechnology is being used to create new crop varieties which are more resistant to extreme weather events
(e.g. drought-resistant millet is being growin in Kenya)
Managing Water Supply
Water Meters
Can be installed in homes to discourage excessive water use
Recyling
Rainwater and waste water can be collected and recycled
Coping with Rising Sea Levels
Hard and Soft Engineering
Better flood warning systems are being put in place, and physical defences such as flood barriers are being built
(e.g. the Thames Barrier in London)
Embankments
In areas that can't afford expensive flood defences (e.g. Bangladesh), people are building raised food shelters and building houses on embankments
Case Studies
Haiti 2010 Earthquake
Primary Effects
316,000 people died
30,000 commercial buildings collapsed / were severely damaged
300,000 had been injured
Secondary Effects
1.5 million made homeless
Cholera outbreak
50,000 put in temporary homes
4000 inmates escaped
Immediate Responses
Aid slow to arrive due to the port being damaged
USA sent rescue teams and 10,000 troops
235,000 people moved away from Port-au-Prince to less damaged cities
Long Term Responses
World Bank reduced the country's debt repayments for 5 years
The port was built after a year - which required a large amount of investment
New homes were built to a higher standard although response was slow
Christchurch New Zealand Earthquake 2011
Long Term Responses
10,000 affordable homes were constructed
water and sewage restored by August 2011 (6 months)
Many NGOs provided support, including save the children
Immediate Responses
~$6-7 million financial aid was provided
300 Australian police officers flew into Christchurch in order to enforce the wall
30,000 supplied with chemical toilets
Primary Effects
water and sewage pipes damaged
181 died
liquefaction destroyed many roads and buildings
Secondary Effects
Schools were closed for 2 weeks
1/5 of the population migrated from the season
five Rugby World Cup matches were cancelled
Typhoon Haiyan 2013
Secondary Effects
6 million lost their income
rice prices increased by 12% by 2014
shortages of food and water
Primary Effects
6000 died
15ft storm surge
40000 homes, schools and airport destroyed
Immediate Responses
1200 evacuation centres setup
Long Term Responses
UNICEF vaccinated children against diseases
cash for work programmes set up
Boscastle Floods 2004
Primary Effects
75 cars washed away
6 buildings washed away
Secondary Effects
Tourism industry took one year to recover
Immediate Responses
Emergency rescues were enacted
Long Term Responses
Environment Agency spent £10 million on improving flood defences
widening and deepening the River Valency channel
Rivers
Landforms
Meander & Oxbow Lakes
Thalweg (fastest flow) is on the outside bend of the river
Erosion (hydraulic action) happens on the outside bend due to the deep channel causing lack of friction and a surplus of energy - which leads to a river cliff
Inside bend = slip off slope as deposition occurs due to a shallow channel, meaning less energy + friction
Overtime the neck of the river gets closer and closer until the river joins together
river takes the shortest course and deposition occurs on both side of the course - which creates an oxbow lake
Waterfalls and Gorges
Waterfalls form where a river flows over an area of hard rock followed by an area of softer rock
The softer rock is eroded (by hydraulic action and abrasion) more than the hard rock, creating a 'step' in the river
As water flows over the step it erodes more and more of the softer rock
A steep drop is eventually created, which is called a waterfall
The hard rock is eventually undercut by erosion. It becomes unsupported and collapses
The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion, creating a plunge pool
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Interlocking Spurs
In the upper course of a river most of the erosion is vertically downwards, creating steep-sided, V-shaped valleys
The river lacks the power to erode laterally so they have to wind around the high hillsides that stick out into their paths on either side
The hillsides that interlock with each other as the river winds around them are called interlocking spurs
Lower Course
Landforms
Floodplains
The floodplain is the wide valley floor on either wide of a river which occasionally floods
When rivers flood, the water slows down, loses energy and deposits the material that it's transporting - which builds up the floodplain
Levees
Levees are natural embankments along the edges of a river channel
During a flood, eroded material is deposited over the whole floodplain
The heaviest material is deposited closest to the river channels, because it gets dropped first when the river slows down and loses energy
Over time, the deposited material builds up, creating levees along the edges of the channel
Estuaries
Estuaries are found at river mouths
The land is close to sea level and the river valley is at its widest
The water here is tidal - the river level rises and falls each day
When the water floods over the banks of the rivers, it carries silt and sand onto the valley floor
As the tide reaches its highest point, the water moves slowly and has little energy, so it deposits sediment
Overtime, more mud builds up, creating large mudflats
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The River Valley
Long Profile
Shows how the gradient changes as you go from the source to the mouth of a river
Rivers have a steep upper course, gently sloping middle course and an almost flat lower course
Cross Profile
Upper
Steep gradient
V-shaped valley
Narrow, shallow channel
Middle
Medium gradient
Gently sloping valley sides
Wider, deeper channel
Lower
Gentle gradient
Very wide, almost flat valley
Very wide, deep channel
Vertical & Lateral Erosion
Vertical erosion
deepens the river valley and channel, making it V-shaped
Dominant in the upper course of the river
High turbulence causes the rough angular particles to be scraped along the river bed, causing intense downwards erosion
Lateral erosion
widens the river valley and channel during the formation of meanders
dominant in the middle and lower courses of the river
Erosion, Transportation and Deposition
Erosion
Hydraulic Action
The force of the river water colliding with rocks breaks rock particles away from the river channel
Abrasion
Eroded rocks picked up by the river scrape and rub against the channel, wearing it away
Attrition
Eroded rocks picked up by the river crash into each other and break into smaller fragments
Their edges also get rounded off as they rub together
The further material travels, the more it is eroded - attrition causes particle size to decrease from source to mouth
Solution
River water dissolves some types of rock (e.g. chalk and limestone)
Transportation
Traction
large particles like boulders are pushed along the river bed by the force of water
Saltation
Pebble-sized particles are bounced along the river bed by the force of water
Suspension
Small particles like slit and clay are carried along by the river
Solution
Soluble materials dissolve in the water and are carried along
Deposition
When the river drops the material it's transporting due to a loss in velocity and a loss in energy
The river slows down maybe because:
The volume of water falls
The amount of eroded material increases
The water is shallower (e.g. on an inside of a meander)
The river reaches its mouth