Geography Revision
Natural Event - An event that causes no damage to life or human infrastructure (buildings).
Natural Hazard – A natural event that poses a risk to lives or buildings.
Natural Disaster – A natural event that causes destruction to buildings and loss of life.
Factors affecting risk of a natural event:
Population density, magnitude, time, frequency, management, education, development, natural
factors.
Plate tectonic theory:
Alfred Wegener suggested continents had drifted apart (100 years ago). Francis Bacon wrote about
how the coastlines of different countries looked like they fit together like a jigsaw (300 years ago).
Evidence of plate tectonics:
Rock Types. Rock types in both continents of Africa and South America were very similar, following
the same patterns too. The two countries must have once been joined together but were separated.
Fossils. Fossils in Africa and South America were similar, which meant that the two continents must
have been joined.
Mesosaurus. 265million years ago Mesosaurus lived, and fossils were only found in two regions:
southern Africa and South America. These two regions are hugely separated so the most reasonable
explanation was they used to be joined, and Mesosaurus could freely traverse through the two.
Ocean Floor Spreading. Scientists found that rocks were older the further you travelled away from
ridges, using carbon dating, which meant that crust was being created and destroyed at certain
points.
Palaeomagnetism. Scientists found that igneous rock on the ocean floor were magnetised in
stripped opposite directions, which meant that when the Earth’s magnetic field reversed in
direction, the new rock being created at ridges were charged oppositely to the older rock.
Hotspots. Lines of islands which used to be volcanoes, could only be explained by plates moving over
hot plumes in the mantle.
Oceanic crust is denser and heavier than continental crust, so is always subducted under continental
crust.
Earthquakes
Earthquakes form on plate boundaries when a build-up of pressure due to friction gets suddenly
released, causing an energy wave to be released.
Earthquakes are measured on the Richter Scale: 1 to 10 and logarithmic (4 to 5 is 10 times stronger).
There is also a Mercalli Scale which measures intensity based on numerous factors, quantifying the
effects of the earthquake. For example, human reactions, natural objects, and economic damage. It
is measured 1 to 12.
The focus is where the earthquake originates from (underground), the epicentre is where the centre
would be if it were overground.
Volcanoes
There are 3 types of volcanoes: Active, dormant, and extinct. Active – erupted recently and is likely
to erupt again. Dormant – hasn’t erupted in 2000 years. Extinct – will never erupt ever again.
Composite Volcanoes:
High in silica (60%), form on destructive plate boundaries where oceanic plate gets subducted and
melts and rises as very viscous, violent, and andesitic magma. This is because air bubbles get trapped
and cannot escape which causes explosions.
Steep with multiple layers of ash and solidified lava.
Shield Volcanoes:
Low in silica (50%), form on constructive plate boundaries, where fluid magma is free to rise from
the mantle, and basaltic magma.
Very flat with no layers.
Plate Boundaries
Constructive
Plates move away from each, allowing magma to rise through the gap to form land. E.g., North
American Plate and Eurasian Plate.
Destructive
One plate (oceanic) gets subducted under another (continental). Shield volcanoes form on
destructive plate boundaries. E.g., Nazca Plate and South American Place.
Collision
Plates continental plates collide and get forced up to form fold mountains. E.g., Indian Plate and the
Eurasian Plate (Himalayas).
Conservative
Two plates slide past each other in opposite directions or in the same direction at opposite speeds.
E.g., Pacific Plate and North American Plate.
Chile and Nepal Case Study
Chile
27th of February, 8.8 Richter Scale. GDP 38th out of 193 countries. HDI 6th out of 193 countries.
Primary Impacts:
500 dead, 12,000 injured, 800,000 affected, 45,000 schools destroyed, most of the country lost
power, water supply, and communications. $30billion in damages.
Secondary Impacts:
Tsunami destroyed coastal cities, 1500km of roads destroyed mainly by landslides, fire at a chemical
plant, drop 9% in GDP due to reduction in tourism, copper production halted and $100s of millions
of wine production lost, widespread looting.
Immediate Responses:
Power restored to 90% of homes in 90 days, route 5 repaired in 24 hours, national appeals raised
$60 million for 30,000 emergency shelters. Emergency services acted quickly.
Long Term Responses:
1 month on government launched plan to rebuild 300,000 homes, Chile had strong economy from
copper exports and could recover without assistance, estimated 4 years to recover.
Nepal
25th April 2015, 7.9 Richter Scale, 109th in GDP, 245th in HDI.
Primary Impacts:
9000 killed, 20,000 injured, 50% shops destroyed, 8 million/33% of population affected, 7000
schools destroyed, 3 million homeless, $5 billion in damage.
Secondary Impacts:
Rice stores inside homes destroyed by rubble which led to food shortages, avalanche on Mount
Everest killed 19 people, avalanche at Langtang led to 250 people becoming missing, landslides and
avalanches led to emergency responses becoming delayed
Immediate Responses:
Helicopter evacuated climbers on Everest, 500,000 tents set up to combat homelessness, field
hospitals set up, China India and the UK sent aid and rescue teams.
Long Term Responses:
Stricter building codes, 7000 schools planning to be rebuilt, roads repaired, Everest base camp
reopened to generate tourism income, 4 heritage sites were reopened to boost tourism into the
country.
Living in Tectonically Hazardous Areas
Why people stay?
Benefits: Earthquakes and volcanoes can allow miners to obtain very rare minerals and elements.
Areas on the coast and next to a volcano may be popular for tourism. Farmers can utilise the fertile
land next to a volcano.
Barriers of Migration: Family and friends. Cost of travel. Job and employment.
Perceived safety: Areas have emergency plans. Hazards occur very rarely. Buildings are specially
made with the risk in mind, reducing the chance of collapse or damage.
MPPP
Monitoring, Prediction, Protection, Planning. Helps reduce risk.
Scientists monitor areas of high risk with special equipment to detect warning signs of tectonic
activity (seismographs). They can also use historical evidence to predict when and where a hazard
might occur. After identifying areas of imminent risk, the country can implement ways to prevent
infrastructure from being damaged (sea walls, earth embankments, strong houses). Countries can
also plan to result in the least damage to life in the occurrence of a natural disaster.
Weather Hazards and Climate Change
Factors that affect climate:
Air masses and prevailing wind. If winds pass over oceans the air will become moist and will carry
moisture, however over land, the air will become dry. If the air comes from the equator it will bring
warmer air than if it came from the poles.
Latitude. Temperature increases the closer you get to the equator because of the curvature of the
Earth. In higher latitudes the sun’s rays are dispersed over a larger area because the angle in which
the sun shines upon is more steep and not flat like in the equator.
Altitude. Every 100 metres you go up, temperature falls by 1c, because less dense air holds thermal
energy less easily.
Distance from sea. Places near the sea have very stable climates all year round because water (the
sea) heats up slowly and cools slowly. In contrast, places away from the sea have very volatile
climates.
Ocean currents. Will affect climate depending on where the ocean current came from. If from a
warmer source, the water will bring warmer climate to the area.
Urbanisation. Roofs, streets, concrete, chemicals, and fumes traps the sun’s heat which increases
the temperature of the area. (Cities are 3 to 10c warmer than countryside)
Global Atmospheric Circulation
Hadley Cell, Ferrell Cell, Polar Cell.
North-East trade wind/South-East trade wind, Westerlies, Polar Easterlies.
Due to the Coriolis effect storms spin clockwise in the southern hemisphere, and anti-clockwise in
the north.
Tropical Storms
Tropical storms form over waters over 27c in temperature, as a cooler temperature would not
provide enough energy to fuel the storm. They also only form 5-15 degrees in latitude because at the
equator not enough spin in generated by the Coriolis effect. Winds must be at least 74mph to be
classified as a tropical storm.
As climate temperatures globally continue to rise, the general hazard area of tropical storms may
move further north and south, because waters will have a lot more thermal energy, enough to fuel a
tropical storm.
Hurricanes are measured on the Saffir-Simpson scale.
Formation of Tropical Storms
On waters with temperatures over 27c water will quickly evaporate. As the water vapour rises it will
cool and release its thermal energy. The vapour will condense into thunder clouds and the heat
energy creates convection to fuel the storm. The Coriolis effect causes the convection to spin in a
certain direction (clockwise in the southern hemisphere) which causes clouds to spin, resulting in
strong winds. An eye will form where cool air sinks. Meanwhile, warm air continues to rise and spin
up the eye wall. The storm is carried to land by prevailing winds and will eventually lose its wind and
energy because its supply of warm water is cut off, unable to fuel the tropical storm. Winds at higher
altitudes also rip the storm apart. Friction from land also slows the storm down.
Structure of Tropical Storms
Outflow cirrus shield. Eye. Eye wall. Rain bands.
MPPP
Monitoring, prediction, protection, and planning. Satellites and radar technology are used to track
the development and approach of a storm. Technology can also predict tropical storms. Protection
involves hard engineering and soft engineering. (Storm walls, storm shutters, mangrove trees, storm
proof houses, shelters, warning systems). Planning involves warning, education, emergency services,
and evacuation plans.
Extreme Weather in the UK
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Heatwaves
Heavy snow
Heavy rain and heavy wind
Droughts
Evidence:
In 2019 highest temperature ever recorded of 38.7c.
In 2009 record amounts of rainfall in the Lake District
In 2010 Northern Ireland recorded -18.7c.
In 2013 it was the UK’s wettest winter in 250 years.
Climate change may have caused the jet stream to ‘stick’ in one position, resulting in a prolonged
weather conditions, which explains why there have been so many droughts, flooding, and
heatwaves.
Typhoon Haiyan and Somerset Level Floods
Typhoon Haiyan
November 2013, Category 5 on the Saffir-Simpson scale, waves 15m high.
Primary Impacts:
6,300 killed, 220,000 homeless, 40,000 homes destroyed, 30,000 fishing boats destroyed, crops
damaged from storm surge.
Secondary Impacts:
6 million jobs lost, landslides and flooding blocked roads, power supply out for a month, looting in
Tacloban.
Immediate Responses:
1,200 evacuation centres set up, field hospitals set up, Philippines’ red cross delivered food aid, UK
government sent shelter kits.
Long Term Responses:
Cash for work scheme set up by the government – fixes unemployment issue and debris issue, rice
farming and fishing re-established, homes built away from flood risk areas, cyclone shelters made
larger.
Somerset Level Floods
December 2013, caused by Atlantic depressions, high tides, storm surges, and lack of river dredging.
Social Impacts:
600 homes flooded, 16 farms evacuated/flooded, restricted access to schools, shops and workplace,
power supplies cut off.
Economic Impacts:
£10 million cost, 14,000 hectares of farmland under water for 2 to 3 weeks, 1000 livestock
evacuated, roads cut off, railway under water.
Environmental Impacts:
Floodwater contaminated with sewage, oils and chemicals, stagnant water had to be reoxygenated
before returned to rivers or may kill river wildlife.
Immediate Responses:
Sandbags to block peoples’ front doors, residents used boats to travel, royal marines helped
evacuation, volunteers helped to support/evacuate people.
Long Term Responses:
£20 million flood action plan by Somerset Council. In 2014 rivers were dredged. Roads were raised.
Flood defences set up.
Management Strategies to Reduce UK Extreme Weather Risk
Dredging increases the wetted perimeter (+embankment too), raising roads allows key economic
transport to occur, tidal barrages (Thames Barrier).
Climate Change
Evidence of climate change: Sea level changes (Average sea levels have risen by 20cm in the past
100 years). Retreating glaciers (arctic sea ice has thinned 65% since 1975). Climate data since 1912
has shown a 0.85c temperature increase globally of average.
Ice Core Analysis – Analysing ice cores allows you to tell the percentage of gases at that time. From
this scientists can work out the temperature from as long as 400,000 years ago.
Describing temperature in the quaternary period:
Over the past 2.6 million years the climate has been fluctuating up and down, with cooler periods
lasting longer. These are called inter-glacial and glacial periods, respectively. These warmer periods
then cooler periods have been happening in regular timings, until around 15,000 years ago.
Temperatures after then have been starting to warm. However, glacial trends suggest the
temperatures should be going down. This is evidence of global warming.
Natural Factors of Climate Change
Milankovitch Cycles
1. Eccentricity. The earth’s orbit varies from a circle to an ellipse every 100,000 years.
2. Axial tilt. The earth’s spin on its axis varies from 21.5 degrees to 24.5 degrees. We are
currently at 23.5 degrees. This affects intensity of seasons.
3. Precession – The wobble of earth’s spin every 26,000 years.
Volcanic Activity
Eruptions release sulphur dioxide which reacts with water vapour to form an aerosol which reflects
the sun’s energy, cooling the earth.
Solar Activity
Sunspot activity changes from a minimum to maximum on a cycle of 11 years. Sunspots give off
more solar flares which results in more thermal energy being transferred to earth.
Human Factors of Climate Change
Burning fossil fuels – fossil fuels released stored CO2 into the atmosphere with causes an enhanced
greenhouse effect that heats the earth too much.
Deforestation – Slash and burn techniques turn organic carbon in the trees’ carbon stores into
carbon dioxide, which causes the enhanced greenhouse effect.
Decomposing organic matter – Landfills, sewage and waste decomposes which releases methane.
Methane is a powerful greenhouse gas which boosts the enhanced greenhouse effect.
Mitigation is the action of reducing the severity, seriousness or effects of something.
We can mitigate human climate change by reducing the amount of carbon dioxide emissions which
is the leading cause of the enhanced greenhouse effect.
Carbon Capture
Uses technology to capture CO2 produced from the burning of fossil fuels. Carbon capture captures
90% of CO2 released. Once captured, carbon gas is compressed and injected in geological reservoirs
(depleted oil and gas fields.
Planting Trees
Trees photosynthesise which absorbs CO2 which is stored as biomass (organic structures).
International Agreements
Paris agreement 2015 – 195 countries signed. $100 billion a year to support climate change
initiatives in LICs. To keep global temperature rises below 2c. LEGALLY BINDING AGREEMENT.
Alternative Energy
Using other energy sources that do not produce greenhouse gases like solar, wind, tidal, geothermal,
nuclear and hydroelectric. Biomass can be used because it is carbon neutral.
Adaptation is adjusting to new conditions.
We can adapt to climate change in a variety of ways. In islands with threat to sea level rise, houses
can be raised on stilts, mangrove trees can be built, and sea walls can be constructed.
In the Himalayas they rely of glaciers for water supply. Now they have retreated, the people are
building artificial glaciers.
In areas with higher risk of drought due to climate change, drought resistant crops can be used to
keep food production at the same level.
Climate Change Effects on the UK, Maldives, and Greenland
In the UK warmer climates have meant higher crop yields. The environment is also thriving. However
extreme weather has meant disastrous economic and environmental loss. For example, floods
damage infrastructure and pollutes freshwater rivers.
In the Maldives due to rising sea levels the whole population will have to move out by 2030. Millions
of trees and animals will die due to salt toxicity.
In Greenland, the whole economy is benefitting because ice is melting. Mining industries are
booming, and they can finally produce crop yield. On the other hand, polar bears are facing an
increasingly smaller natural habitat.
Coastal Landscapes
The coast is the dynamic zone where the land meets the sea and coastal processes occur.
Waves form when blows over the ocean which causes convection of energy in the water. These
convections travel to the shore. When reaching the shore, the convections encounter shallower
water due to the shallow seabed. This causes friction to act against the bottom of the convection,
which causes the top of the wave to travel faster than the bottom. This makes the water rise up and
over the bottom water. This is how a wave forms.
Size and energy of waves depends on:
Fetch – How far the wave has travelled
Strength of wind
How long the wind has been blowing for (when there is a storm0
Destructive Waves
Weak swash, strong backwash.
Very steep (higher than wide)
Tall breaker breaks downwards with great force which producing a strong backwash which removes
sediment from the beach.
Constructive Waves
Strong swash, weak backwash.
Very low (wider than high).
The wave doesn’t have a high breaker and instead ‘spews out’ onto the beach, depositing its
sediment carried with the energy.
Weathering is disintegration of rocks in situ from processes above.
Mechanical
A weathering processes. For example, freeze thaw. Water enters a crack or crevasse. It freezes and
expands by 9%. The crack widens. The process repeats.
Another process is salt weathering. Salt spray gets into cracks. The water evaporates, allowing salt
crystals to form. The cracks widen and the process repeats.
Biological
Flora and fauna weathering. Tree roots can grow through rocks which causes them to widen and
break off. Also, burrows can weaken cliffs and can make them easier to break off.
Chemical
Carbonation. Carbonic acid reacts with calcium carbonate (limestone) which forms calcium
bicarbonate which dissolves in water and washes off. This eventually erodes the limestone.
Mass Movement is the movement of weathered material.
Rockfall
When bits of rock fall off the cliff face (usually from freeze thaw weathering).
The fragments on the ground are called scree.
Mudflow
When saturated soil flows down a slope.
Due to chemical weathering fibres and roots in the soil break down which weakens the soil. When
the soil becomes saturated it becomes liquified and flows down the gradient. The lobe is where the
saturated mud collects at the bottom of the hill.
Landslide
When large blocks of rocks slide downhill.
Clay in between rock layers acts like a lubricant which allows weathered rock to slide straight down
the slope. The layers are called beddings of rocks.
Rotational Slip
When saturated soil slumps down a curved surface.
Heavy saturated soil bears down on a cliff. The section of the cliff face tears away from the curved
slip plain due to gravity and slides down.
The scarp is the area where soil has been exposed due to the slip. Material collects at the bottom of
the foot at the toe.
Coastal Erosion
Abrasion – Pebbles constantly hitting and grinding against a rocky platform often causing it to
become smooth.
Attrition – Small rock fragments suspended in the water hit into each other, causing them to erode
into finer sediment and smoother.
Hydraulic Action – The power of the waves as they hit onto the cliffs
Corrasion – Rock fragments are thrown by the energy of waves into cliffs, which gouge away at the
cliff.
Solution – Soluble chemicals getting dissolved by the water (limestone in carbonation).
Longshore Drift
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Prevailing wind approaches a beach at an angle, therefore so will the waves.
Swash carries sediment up the beach at an angle.
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Backwash pulls sediment down the beach straight down 90 degrees to the coast (steepest
gradient).
Sediment gets carried along the beach in a zigzag pattern.
When the waves lose energy, the sediment gets deposited further down the beach
Sediment is deposited when: Waves lose energy. In shallow water. Calm conditions.
Coastal Erosional Landforms
Headlands and Bays
In discordant coastlines there are layers of hard and soft rock. Soft rock gets eroded quicker than
hard rock. This leaves the hard rock jutting out as a headland. The area where the soft has eroded is
called a bay. The bay stops eroding at a certain point because it is sheltered (waves entering lose
their energy due to refraction. The waves bend their energy towards the sides of the headlands
instead of forwards.
Wave Cut Platform
Weathering (biological, chemical, and physical) weakens the top of a cliff. Waves break against the
bottom of the cliff and erosional processes like abrasion and hydraulic action erode the bottom on
the cliff. This leaves a notch which gets bigger and undercuts the cliff. The overlying weathered cliff
becomes too weak to support its own weight and collapses, leaving a wave cut platform. The process
repeats and the cliff retreats.
Cave, Arch, Stack, Stump
Waves converge onto headlands due to refraction. Small cracks in the rock become enlarged due to
hydraulic action. Over time these cracks become very wide and turn into caves.
Over time, the caves will get attacked by erosional processes like abrasion and hydraulic action,
which will cause the cave to cut all the way through the headland. This leaves us with an arch.
The top of the arch will get weathered by biological and physical weathering and will weaken. The
waves will erode the base of the arch via abrasion and hydraulic action and undercuts the arch. The
arch becomes bigger and will eventually collapse when it cannot support its own weight. This leaves
us with a stack.
The stack gets eroded by the sea and weathered from the air and processes from above. The stack
gets smaller and turns into a stump.
Coastal Depositional Landforms
Beaches
Beaches are deposits of sand and single at the coast. Sandy beaches are found in sheltered coasts
where waves do not have enough energy, so deposit their sediment. Sandy beaches are also found
in coastlines where there are constructive waves.
Sand Dunes
An embryo dune forms around deposited obstacles. This dune eventually builds up in a sheltered
area without wind. Vegetation grows on the dune which stabilises it and it eventually becomes a
fore dune or tall yellow dunes. After a while rotting vegetation adds nutrients into the sand which
causes more plants to colonise the dune, forming black dunes. Winds form depressions in the sand
which are called dune slacks.
Spits
Prevailing wind determines the direction of longshore drift. When longshore drift happens past a
change in the coastline, the sediment gets deposited out to sea, which leaves a spit. Short term
changes in wind direction form a recurved end.
Mud builds up behind the sheltered spit and turns into a saltmarsh where vegetation can grow.
Bars
When longshore drift happens over a headland and past a bay, connecting two headlands, a bar
forms. A freshwater lagoon forms behind the bar, as saltwater cannot get past the bar.
Swanage, Medmerry, and Lyme Regis Case Study
Swanage
Dorset in the south coast of England.
Landforms of erosion: Headlands coincide with resistant rock like limestone and chalk. Clay and
sands are soft and get eroded to form bays. Swanage bay.
Arches, stacks and stumps have formed Old Harry Rocks at Ballard Point.
Landforms of deposition: Two spits have formed at the entrance to Poole Harbour.
At Studland Bay there are lagoons, saltmarshes and sand dunes.
Wide sandy beaches at Studland Bay because of sheltered.
Stakeholders: Tourists, Businesses, Conservationists, Council, Residents.
Medmerry
An example of manage retreat.
Flat, low-lying lying land mostly used for farming and caravan parks. Very low value land so it was
not worth it protect any longer.
Costed £28 million in November 2013.
Created a large saltmarsh in intertidal zone, which acts as a natural buffer to the sea. Embankments
carry on protecting the farming land and caravan parks from flooding.
Large wildlife habitats established and encourages visitors to go to the area, bringing tourism income
into the area.
Lyme Regis
Background Information
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Famous Jurassic Coast famous for its fossils.
Popular tourist town: 15,000 population in the summer.
Reasons for Management
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Unstable cliffs which are rapidly eroding due to powerful destructive waves from the south
west.
Many properties have been damaged.
Sea wall has been breached many times.
Management Scheme
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Completed in 2015 - £43.2 million
New 390m sea wall and promenade
Cliff stabilisation through pinning protecting 480 homes
Beach re-profiling
Beach replenishment/nourishment
Extension of rock armour (at The Cobb)
Pros and Cons
New beaches have increased tourism boosting the local economy and businesses. New defences
have been effective against recent storms, prevent any property damage. Harbour better protected,
allowing more security for fishermen – more looking to enter the fishing business.
However, there are some cons. Increased visitors have meant that there is more congestion which
the locals are not happy about. The new defences also spoil the view for the locals and the defences
are causing sediment starvation down the coast.
Reducing Conflicts
Consultation meetings set up for different interest groups to discuss issues and how to solve them.
Public kept well informed on any construction work that is planned to take place.
Hard engineering is the use of artificial structures to control natural processes.
Sea Walls
Concrete barriers to absorb wave energy. Curved to reflect energy back out to sea. Costs £10,000
per metre. (1 million per 100m) Pro: very effective at stopping wave damage. Con: Looks very
unnatural and extremely expensive.
Groynes
Timbre or rock structures which are built out to sea to trap sediment from being transported by
longshore drift. This helps maintain a wide beach, which acts as a buffer to wave energy from
damaging coastal towns. £250,000 per 200m. Pro: Effective at stopping LSD, giving a very beautiful
beach. Con: Starves beaches further down the coast of sediment, leading to more erosion there.
Rock Armour
Piles of large boulders dumped at the foot of a cliff to absorb wave energy, protecting cliffs from
damage. £200,000 per 100m. Pros: Cheap and provides interest into the area. Increases tourism.
Cons: Obtrusive and doesn’t fit with local geology.
Gabions
Wire cages filled with rock that buffer against wave energy, protecting the coastline or cliffs. £50,000
per 100m. Pro: Get vegetated and can blend in with landscape. Con: Only lasts 5-10 years before
cages rust away and breaking.
Soft engineering is working with natural processes to protect beaches and human infrastructure and
property.
Beach Nourishment
Addition of sand or shingle onto a beach to increase beach width to act as a buffer to waver energy.
Pros: Increases tourism and is cheap. Cons: Needs constant maintenance and erodes very fast.
£500,000 per 100m.
Beach Reprofiling
Changing the gradient or shape of a beach in order for best absorption of wave energy, which slows
down erosion. Pros: Attractive and increases tourism. Cons: Can be quickly eroded by wind and sea,
needs constant maintenance. £50,000 per 100m.
Dune Regeneration
Planting vegetation on dunes to stabilise them, which provides a natural barrier against waves
damage. Pros: Cheapest and creates wildlife habitats. Cons: Can be damaged by storms and is very
time consuming (tourists will trample the dunes). £200 per 100m.
River Landscapes in the UK
The long profile of a river is the gradient of the river from the source to the mouth – it is steeper in
the upper course and gradually flattens out.
The cross profile of a river is an image cut across the river to see the shape of the valley and channel.
Upper course:
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Shallow, narrow channel – because there is less energy upstream, so the water does not
have enough power to erode a large channel.
Steep narrow valley – very steep gradient upstream (long profile) which means that there is
more vertical erosion as the force of gravity is pulling the water down more. This carves out
a very narrow V-shaped valley.
Vertical erosion – very steep so lots of gravitational force on the water.
Load particle size is large, but the load quantity is small – this is because upstream there has
not been enough time for erosional processes like attrition to take place which means that
sediment is quite large. Load quantity increases downstream because the river has more
energy than upstream so can transport sediment easier (though traction, saltation, and
suspension).
Middle Course:
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Wider, deeper channel
Shallower valley sides
More lateral erosion
Lower course:
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Wide, deep channel – lots of river energy erodes a larger wetted perimeter.
Wide, open valley (floodplain) – mostly lateral erosion which creates a large flat floodplain
due to the meanders of a river.
Load size increases due to an increase in time for erosion to happen.
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Velocity is greatest in the lower course because of greater efficiency (smoother channel bed
due to more friction due to more energy. Also, relatively more volume of water to surface
area touching the channel bed so proportionally less friction) and greater energy.
Vertical erosion: cutting down into riverbed.
Lateral erosion: sideways erosion into the riverbanks.
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Discharge down a river increases because of increased water supply from the whole
drainage basin, tributaries join in a confluence to form a bigger river. The wetted perimeter
also increases downstream which allows more water to flow through the river.
Occupied channel width increases because there is more lateral erosion than vertical
erosion, which causes the river to widen.
Channel depth increases because down a river, the water has more energy which allows it to
erode and carve out a bigger area for water to flow.
Velocity increases downstream because of increased efficiency (smoother channel bed from
increased erosion) and increased energy (GPE turns into kinetic energy).
Load quantity increases because energy increases which allows the river to carry more
sediment.
Particle size decreases because there is more time for erosion (attrition).
Channel bed roughness decreases because sediment has been wearing away so obstructions
like boulders do not increase friction. There is also more energy, so roughness gets eroded
away.
Gradient decreases downstream which means that there is less vertical erosion (long profile)
Erosional Processes
Abrasion is the grinding of rocks on a surface which causes it to become smoother and eroded away.
Solution is when the water causes rocks or other sediment to dissolve into solution which can then
be washed away by the water, eroding the rock.
Hydraulic action is the force of the water against rocks. This involves water forcing air in cracks to
shatter rocks.
Attrition is when rocks and sediment in a river crash into each other which causes the sediment to
become finer and smoother.
Corrasion is when rocks are picked up by the water and thrown at rocks above the water level. This
usually only happens at the coast but can also happen in rivers.
Transportation
Traction is the rolling of heavy sediment like large rocks along the riverbed.
Saltation is the bouncing of medium mass objects along the riverbed.
Suspension is when sediment is carried in the water due to high water energy and the sediment
rarely touches the bed or banks.
Solution is when sediment s dissolved in the water and is carried with the water.
Landforms
Of erosion
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Interlocking Spurs – Where a river weaves through hills. The river doesn’t have enough
energy to cut through the spurs of land, so it goes around them.
Waterfalls and gorges- 1. River erodes soft rock and leaves hard rock leaving a step (the
layer of soft and hard rock must be in a triangular layer). 2. As the step deepens, water
erodes out a plunge pool. 3. The hard rock is then undercut through the erosion of soft rock
because of increased erosion in the plunge pool due to lots of attrition abrasion and
hydraulic action. 4. The hard rock collapse as it is no longer supported, and rock fragments
go into the plunge pool. 5. The waterfall moves back, leaving a steep valley called a gorge.
Of erosion and deposition
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Meanders and oxbow lakes – Meanders are side bends of a river due to lateral erosion. 1.
Differences in depth on two sides of a river cause water to travel at different velocities. 2.
On the rapid side the water erodes fast causing the river to shift towards that side. On the
slow side the water deposits sediment due to low energy. 3.This causes the river’s bend to
become more extreme.
Riffles are the shallow sections in the inside bend of a meander and a pool is the deep
section on the outside of a bend.
Oxbow lakes form when the neck of a meander gets narrower. During times of flooding the
neck of the meander breaks through, which allows a straight passage for water. Water
favours this path as it has the least resistance. The old meander is now blocked off through
deposition because it is very calm. What is formed is an oxbow lake.
Of deposition
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Levees – When a river floods the heaviest sediment is deposited first, which is near the
channel. Over time and many floods this builds up into a levee – a ridge on the bank of
rivers.
Floodplains – When meanders migrate across the land, they erode at the valleys. This leads
to a very flat, wide valley. The edge is called a bluff. During flooding, alluvium and silt is
deposited onto the floodplain. This causes the floodplain to become very fertile.
Estuaries – the transitional zone between a river and the sea and they are tidal. During low
tide, sediment can be deposited in the shallow sides of a river which form mudflats.
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Deltas – when the sea at the mouth of a river is not strong enough to carry sediment away
from the mouth of the river, the sediment builds up which builds deltas. The river then splits
up into lots of small rivers which travel along the deposited sediment.
The River Tees
Pennine Hills in the North-East of England.
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High force waterfall – 20m drop of some limestone and hard dolerite.
Low force waterfall
Gorge in front of waterfall west of Darlington
Levees and Floodplains near Darlington
Meanders south of Darlington
Estuary and mudflats at the mouth of the river in Middlesbrough
Hydrographs
Hydrographs show the discharge of water in a river responding to a specific rainfall event over a
period of time in a certain location.
They can either be subdued (long lag time) or flashy (very short lag time).
Factors affecting hydrographs and flood risk
Characteristics of a drainage basin
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Size – a smaller drainage basin means that rainfall reaches the channel more rapidly via
surface runoff, lowering the lag time.
Shape – an elongated drainage basin will have a longer lag time because water from the
extremities will take much longer to arrive at the channel. This means that the maximum
water discharge peaks later. In a circular drainage basin lag time will be very short because
all the water reaches the channel at once.
Drainage density – a high density of rivers will speed up water transfer into the main channel
so will cause a flashier hydrograph (lower lag time).
Types of Precipitation
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Prolonged rainfall – rainfall already taken place before the event will lead to saturation of
the ground, which reduces the rate of infiltration, which increases surface runoff, leading to
a shorter lag time, as water arrives to the channel faster.
Intense storms/Flash floods – causes saturation of the soil which reduces infiltration.
Preceding weather conditions – hot, dry weather causes soil to get baked hard which leads
to water being unable to infiltrate under the ground.
Snowfall – melt water rapidly increases water volume. Frozen ground also means there is
more surface runoff.
Geology
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Permeability of underlying rock – impermeable rock means water cannot infiltrate which
increases surface runoff.
Soil type – impermeable soil increases surface runoff because water slides right past and
does not get absorbed.
Land Use
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Urbanisation – concrete reduces infiltration which increases surface runoff significantly.
Deforestation – trees intercept 80% of rainfall in the Amazon. Deforestation significantly
decreases rainfall that is intercepted and rainfall that is transpired which increases the
volume of surface runoff.
Agriculture – arable farming leads to more surface runoff. If land is ploughed along gradient,
then water can flow through faster.
Relief
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Steep land will lead to faster surface runoff due to a larger force of gravity. This means that
the lag time will be shortened and peak discharge increases.
Flooding occurs when too much rainfall leads to a rapid increase in the volume of water a river
carries. Once a river can’t carry any more water, it overtops its banks and water spews out onto the
surrounding land.
Flood Management Strategies
Hard Engineering the use of man-made structures to control natural processes.
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Dams – very expensive and flood large amounts of land – effective at flood prevention,
recreation, water storage, HEP.
Embankments – increase the wetted perimeter – very effective at allowing river to hold
more water – looks ugly and unnatural.
Channel Straightening – protects area well because water is quickly moved out of the area –
leads to increased flooding downstream.
Relief Channels – creates new wetlands and habitats and controls flooding – very expensive
to build a whole man-made river.
Soft Engineering working with natural processes to control flood risk.
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Zoning – reduces overall losses of flooding – very hard to implement in areas already built on
floodplains, house prices fall in the area.
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Afforestation – increases interception and transpiration – cheap – may waste to much land
that could be used economically to build houses or farmland.
River restoration – letting a river return to its natural state – natural processes like meanders
and wetlands naturally slow down a river which lowers flood risk downstream – increases
flood risk at that location.
Warnings and preparation – monitoring prevention protection planning – allows people to
save some expensive property – property will still be damaged during flooding at the area
will be considered at flood risk and property prices will fall. It helps protect human life.
Banbury Case Study
Located in the Cotswold Hills 50 km north of Oxford.
Banbury located on floodplain of the river Cherwell.
Why it was needed
History of flooding – in 1998 the train station was closed due to flooding and it costed £12.5 million
in damages, affecting 150 homes and businesses – in 2007 it flooded again.
Strategy
Completed in 2012 – an earth embankment 2.9km long parallel to the M40 to create a flood storage
area (3 million cubic metres of water) controlled by floodgates – A361 raised – new pumping station
– biodiversity action plan (ponds, trees and hedgerows to absorb excess water.
Social Effects
Raising A361 avoids disruption to human activities. New footpaths and nature areas improve quality
of life. Reduced anxiety.
Economic Effects
£18.5 million. Protects 441 homes, 73 commercial properties. Estimated benefit of $100 million.
Environmental Effects
New BAP creates range of habitats. Flood storage area is a natural flood plain – creation of a wetland
allows more habitats and wildlife – 100,000 tonnes of earth had to be dug up to build embankments.
Ecosystems
Ecosystem – natural systems made up of plants and animals. Complex relationships exist between
the living and non-living components which interact with each other.
Biotic components – the living features of an ecosystem (fish, birds)
Abiotic components – the non-living features of an ecosystem (climate, water, light)
Producers – convert energy from the environment into sugars.
Consumers – gets energy from the sugars produced by producers.
Decomposers – breaks down plant and animal material and returns the nutrients back to the soil.
Food chain- shows the direct links between producers and consumers in a simple line.
Food web – shows all the connection between producers and consumers.
Nutrient cycling – nutrients are essential elements that are used by plants and animals to build their
organic molecules. When animals die decomposers return the nutrients inside animals and plants
into the soil again, allow them to be available to other life forms. Nutrients can come from the
atmosphere or weathered rock.
A freshwater pond
Is a small-scale ecosystem found in the UK.
Abiotic (non-living) factors include the oxygen concentration in the water and sunlight
concentration. Soil composition is also a factor.
Biotic (living) factors include ducks and midge larvae on the pond surface. In the mid-water species
like perch and beetles can be found. In the pond bottom water worms and rat-tailed maggots are
found. Out on the side surface of the pond reed mace is found as well as animals like herons.
These different biotic components interact through predator-prey relationships in the food web.
Impacts to ecosystems
Ecosystems can adapt to slow natural changes. However, when a change is too sudden it can have
huge impacts on the entire ecosystem because factors in the food web are affected.
Human impacts include eutrophication, hedgerow removal, deforestation, and pond draining for
farmland.
Avington Park Lake
The lake was restored in 2014. Silt was removed and it was redefined. This led to a boost in the
number of species in the ecosystem, full of a wide range of habitats.
Large Scale Ecosystems
Large scale ecosystems are known as biomes.
All large-scale ecosystems are caused by global atmospheric circulation and factors that affect
climate (latitude, altitude, distance from sea, air masses, ocean currents).
Tropical Rainforests
High temperatures and high rainfall due to GAC. There is low pressure because air is rising. This
causes the air to condense into rain clouds and release all their moisture. It is very hot because it is
on the equator.
Deserts
Very dry because of high pressure belts bringing very dry air via the Hadley cell.
Tropical Grassland
Called savanna. Not as wet as tropical rainforests, and not as dry as deserts. (15 to 30 degrees
latitude)
Temperate Grassland
Cooler that deserts, but quite dry, but not as much.
Deciduous and coniferous forests
Quite wet due to low pressure due to the Ferrell cell. Quite cool too. Deciduous tree shed their
leaves whereas coniferous trees do not. The UK is deciduous naturally.
Mediterranean
Hot summers and mild wilders. Located 45 degrees North.
Tundra
Very cold and quite dry. Low growing plants are well adapted to retain heat in this harm
environment.
Polar
Very cold and very dry due to the sinking of the Polar cell.
Tropical Rainforests
Climate in a tropical rainforest is quite stable. Temperature is always high around 31-33 degrees.
Rainfall is high with some fluctuations in the dry and wet seasons. This is because during some
periods the low-pressure belt is right overhead, which causes very high rainfall.
Ground Layer
The forest soil is very infertile, so plants receive nutrition from decomposing organic matter. Roots
are very shallow to adapt for this. Buttress roots are found here to anchor trees into the ground and
obtain nutrients and also increase oxygen and carbon dioxide gas exchange. Tigers, pumas, boar,
and mushrooms are found on the ground layer.
Lower Tree Canopy
Lianas are plants that use trees to climb up. Allowing them to receive enough light for energy and
flowers. Plants and animals here have evolved to camouflage within the trees.
Canopy
Epiphytes hang on branches high in trees to receive plenty of sunlight. They get their food and water
from the air not the ground.
Emergent
The kapok tree outgrows all other trees to receive the most sunlight. It has large buttress roots to
anchor itself down. Leaves are flexible to face the sun at all times. Leaves have a ‘drip tip’ to allow
rainfall to drip easily off the plant.
Interdependence between species: The Kapok tree and Macaws. Plants and climate. Plants and soil.
Epiphytes and trees. Lianas and trees.
Malaysia Case Study
Malaysia is located on two places. The peninsular Malaysia and East Malaysia in Borneo.
Natural vegetation in Malaysia is tropical rainforest making up 67% of land coverage.
Timber in Malaysia is very valuable and deforestation in Malaysia is happens incredibly fast. More
than in any country in the world.
Causes of deforestation
Logging
Malaysia was the largest exporter of tropical wood in the 1980s.
Mineral extraction
Tin is mined in Malaysia which requires large areas of forest to be removed when deposits are
found.
Commercial farming
Malaysia is the world’s largest exporter of palm oil. Palm oil plantations receive 10-year tax
incentives. A rapidly increasing area of rainforest is being turned in plantations.
Subsistence farming
Slash and burn techniques can spiral out of control and leave large areas of rainforest removed. In
small scales it is sustainable.
Population pressure
In the past people were encouraged to migrate to the countryside from the rapidly growing cities.
15,000 hectares of forest have been felled for settlers.
Road building
An increase in development, mining, and energy projects require lots of roads which must have a
clear path.
Energy development
The Bakun Dam is 205 metres high and is the highest dam in Asia outside China. It flooded 700km^2
of forests and farmland. Energy developments require large portions of forest to be cleared, which
seems to swarm Malaysia.
Impacts of Deforestation
Soil erosion
Tree roots and plants help bind the soil of a rainforest together. After deforestation, the soil gets
exposed to lots of wind and rain and will erode away very quickly.
Loss of biodiversity
Deforestation destroys habitats and ecosystems. This reduces the number of species in an
ecosystem significantly, which reduces biodiversity – how many animals and plants are living in the
area.
Contribution to climate change
Trees are carbon stores. Once cut they will either rot or be burned which releases the carbon store,
which contributes to the enhanced greenhouse effect. Trees also give off moisture and heat by
transpiration. Without the rainforest the climate would be very dry and hot and may lead to
desertification as the soil is eroding away too.
Economic development
Deforestation leads to increased business in the mining sector, timber exports, HEP power, and
agriculture production in palm oil and rubber. This has led to increased government tax revenue in
Malaysia which has led to improved infrastructure and quality of life of the population on Malaysia.
However, in the long run it may decrease economic developments. Increased climate change will
lead to losses in economic development as people will have to adjust to living in a warmer climate.
Medical benefits will also be lost, as forests provide a large number of new medicines that can treat
all sorts of diseases.
Why should we protect rainforest?
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Biodiversity – rainforests are home to thousands of species. Thy may become extinct before
we even discover some species.
Climate Change – released carbon stores lead to an enhanced greenhouse effect.
Climate – rainforests prevent the climate from being too hot and dry (they release moisture
back into the atmosphere via transpiration).
Medicine – 25% of medicines come from tropical plants. 2000 tropical plants have anticancer properties.
Resources – rainforests provide valuable resources like nuts, fruit, and rubber which we
must conserve.
Water – rainforests are a major source of freshwater – 20% of world’s freshwater comes
from the amazon basin.
People – indigenous tribes live in harmony with rainforests and placing them in cities will
lead to mass poverty and deprivation.
Sustainable Management of Tropical Rainforests
Selective Logging
Identifies species that are fine to log and will not cause lasting damage to the rainforest. Don’t log
sapling trees. Trees are marked to fell, making sure that only a small proportion are cut to maintain
the ecosystem. After felling the area is surveyed to make sure there is no permanent damage. The
trees are replanted and the cycle repeats after 40 years.
Pros: eco-friendly. Cons: very expensive.
Conservation and Education
Rainforests can be protected by using national parks and nature reserves. Areas can be protected for
scientific research and tourism.
Pros: cheap and effective. Cons: Illegal loggers will still can, and conservation prevents the locals
from creating economic growth.
Ecotourism
Introduces people to the natural world, and also benefits the local people and government. Profits
from ecotourism go to conservation. Income generate means that people no longer need to deforest
in order to make a living.
Pros: Protects rainforests. Cons: Footpath erosion.
International Agreements
Restrictions on hardwood use because mahogany trees take 150 years to reach maturity.
Debt relief prevents deforestation because it stops countries from deforesting to pay off debts (in
2010 the USA relieved £13.5 million of Brazil’s debt to protect the rainforest).
Cold Environments
Cold environments are areas that experience temperatures of 0 degrees or below for extended
periods of time.
Polar – winters below -50 degrees, little precipitation.
Tundra – An area where the subsoil is permafrost which hinders tree and plant growth. In a tundra
there is a short summer where there is a growing season.
Polar bears are adapted by having a thick fur, a thick layer of fat, and a black nose and foot pads to
absorb sunlight heat.
Bearberries are adapted by growing very low (5cm) and hairy stems to retain heat. Bright red berries
are easily spotted to allow birds to distribute the seeds.
Cold environments are low energy environments which means that food webs are very linear
because of low quantities of producers. This makes cold environments very fragile ecosystems.
When one species goes extinct it will have massive effects for all other species. Limited nutrients and
short growing seasons also mean that damage to plants will take a long time to recover.
Svalbard Case Study
Located in the Arctic Ocean. 60% of land is covered by glaciers and has a population of 2700.
Opportunities
Mineral Extraction
300 people employed in mining. In 2014 a new mine opened with a road over a glacier.
Energy Developments
Lots of coal mining industry. Coal power station at Longyearbyen. Huge geothermal potential
development because it is situated close the mid-Atlantic ridge plate boundary.
Fishing
150 species of fish living around Svalbard in the Barents Sea.
Tourism
In 2011, 70000 people visited Longyearbyen and 30000 were cruise passengers. Tourism provides
300 jobs. Tourists come to see the northern lights and to see the natural environment (glaciers,
polar bears).
Challenges of development
Extreme Temperatures
Temperatures fall below -30 degrees. People must wear 4 layers of clothing.
Construction
Working outdoors with low visibility, extreme temperatures, and thick clothing make construction
very challenging. Permafrost building needs to be checked to make sure during melting the building
does not collapse.
Services
Pipes must travel overground to avoid melting the permafrost and to allow easy maintenance.
Accessibility
There are very few flights and travel to Svalbard is very restricted.
Protecting Cold Environments
Cold environments hold lots of coal, gas, and oil reserves which are very valuable. Economic
developments must build lots of infrastructure including accommodation for workers, roads through
forests and tundra, and pipelines built.
Why protect?
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Many species live in cold environments and are fragile so have high risk of going extinct from
economic developments.
Tourism views
Opportunities for forestry or fishing
Beauty
Management
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The use of technology (the trans-Atlantic pipeline) – in 1974 the pipeline was opened
enabling oil to be transported 1300km from Prudhoe Bay to the port of Valdez. Pumping
stations keep oil moving through the pipe and it is raised to allow animals to pass through
and insulated to not melt any permafrost. When a leak occurs the flow automatically stops.
Action by governments (Alaska) – National Environmental Policy Act – ensures oil extraction
protects the environment and native people – Western Arctic Reserve – 9 million hectare
protected wilderness free from oil drilling due to caribou and polar bears. – NOAA –
oversees fisheries in Alaska to protect marine habitats and ensure sustainable fishing.
International agreements – in 1959 the arctic treaty was signed to protect the wilderness in
cold environments reducing economic developments. It controls tourism to avoid
disturbance.
Conservation groups (WWF) – protects artic environments by working with oil companies to
reduce their impact, research, and works with local communities to help endangered
species.
Wilderness areas are areas free from human activity and economic growth.
For developing on them: 4 million already live in the arctic fine. Technology allows cold
environments to be exploited without environmental damage. Cold environments are rich in natural
resources.
Against developing on them: wilderness areas are fragile and easily damaged by economic activities.
Rare plants and animals will be protected. Untouched areas offer extensive scientific data.