- Created by: FatmaAwes_
- Created on: 17-05-18 21:56
What are winds?
- Large scale movements of air caused by differences in air pressure.
- Differences in air pressure are caused by differences in temperature between equator and poles.
- Winds move from areas of high -> low pressure.
- Part of global atmospheric circulation loops.
- Have warm rising air (low pressure) and cool falling air (high pressure).
What are the names of the three cells?
What occurs to form the cells?
- Sun warms earth which transfers heat to air above, causing it to rise = low pressure belt with rising air, clouds and rain.
30 degrees N and S of Equator:
- As air rises from equator, it cools and moves out to 30 degrees N and S. Cool air sinks, creating a high pressure belt with cloudless skies and very low rainfall.
Cool air reaches the ground surface and moves as surface winds either back to the equator or towards the poles.
60 degrees N and S of Equator:
- Warmer surface winds meet colder air from poles, warmer air is less dense so it rises, creating low pressure.
- Some of the air moves back towards the equator, and rest moves towards the poles.
- At poles, cool air sinks, creating high pressure is drawn back towards the equator as surface winds.
What causes variation in climate?
Pressure belts caused by global atmospheric circulation.
Describe the different climate zones around the wo
- Temperatures low all year round.
- Moderate summers and winters, low pressure belt at around 60 degrees N and S caused by rising air from two cells meeting = frequent rainfall.
- Temperatures are hot all the time, rainfall is high. Usually near the equator, where rising air from two cells meeting = low pressure = rainfall. 0 - 5 degrees N and S.
- Low rainfall all/most of year. Temperatures are hot/warm. Usually near 30 degrees N and S, where sinking air from two cells meeting causes high pressure = no rainall.
Global atmospheric circulation -> extreme wind?
- Wind = air moving from areas of high to low pressures.
- This means that atmopsheric circulation causes winds, making some parts of the world winder than others.
- Winds are weak in high and low pressure belts.
- Winds are strong between pressure belts.
- When the difference in pressure is large, winds can be extremely strong. Eg. North Coast of Australia.
Global atmospheric circulation -> extreme temperat
- Equator recieves most energy from sun, poles recieve the least.
- Heat dries atmospheric circulation as warm air from equator moves towards the poles.
- Temperatures can be very high in high pressure areas around 30 degrees N and S.
- There are few clouds due to sinking air, little to block Sun's energy.
- Contrast: temperatures of polar regions like Artic and Antarctic are very low.
Global atmospheric circulation -> extreme precipit
- Precipiation (rain, snow, etc.) occurs when warm, wet air rises and cools, causing water vapour to condense.
- Low pressure belt = air rises = frequent, intense precipitation = rainforests are usually present.
- High pressure belt = air sinks = extremely low precipitation = deserts are usually present.
- Exact location of high and low pressure belts varies over time.
- Places that normally have more moderate weather can sometimes experience extremely dry or wet weather if they find themselves in a high or low pressure belt.
Compare the precipitation in Australia and the UK.
- Australia has a much lower precipitation than the UK = world's driest inhabited continent.
- Average rainfall in Australia = 465 mm.
- Average rainfall in UK = almost double Australia's.
- Extremely wet years in Australia = over 550 mm.
- Extremely wet years in the UK = over 1210 mm.
- Extremely dry years in Australia = less than 360 mm.
- Extremely dry years in the UK = less than 950 mm.
Compare the winds in Australia and the UK.
- Australia has stronger extreme winds than UK, affected by tropical cyclones = winds over 118 km/h.
- In UK, gales (winds over 62 km/h) are rare, most places only experience a few days of gales each year.
- Strongest wind recorded in Australia = over 400 km/h.
- UK's strongest ever sea level wind = over 220 km/h.
Compare the temperature in Australia and the UK.
- Australia is warmer than the UK, warmer summers and milder winters.
- Darwin, northern Australia has a max sum temp = 33℃ where temperatures over 40℃ are considered extremely hot.
- London has a max sum temp = 23℃ where temperatures over 30℃ are considered extremely hot.
- Australian summers are about 10℃ warmer than UK summers.
- For both, extreme temps in summer are about 7℃ warmer than average temperatures.
Ingredients for a tropical storm to form:
- Sea temperatures need to be 27℃ or warmer
- Storm must develop over warm water - allows condensation of warm, moist air to cause extreme precipitation, which releases huge amounts of energy -> storms are powerful. Rising air = low pressure = increase in surface winds.
- Ocean depth needs to be 60 km. The warm water must be deep enough to increase the energy available. Water temperature decreases with depth; the deeper the water, the lower the temperature. This is even true in warm tropical waters. But during the summer months the water slowly heats from the surface down. Eventually, deeper waters may be warm enough to provide the energy needed to increase the storm’s intensity.
- There should be very little wind shear in the area. Wind shear occurs when there is a difference in wind speed and direction over a short distance. Strong wind shear can stop the formation of hurricane eye walls.
- A rapid cooling of air temperature with height allows for condensation to occur and quick development of more cloud formation in the storm wall.
How can the coriolis effect cause tropical storms?
- The rotation is caused by the Coriolis effect, makes moving objects appear to curve toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere because of the Earth's rotation.
- Wind and ocean currents are affected by Earth's rotation.
- Hurricane cloud walls rotate counterclockwide in the Northern Hemisphere and clockwise in the Southern Hemisphere.
How can tropical storms cause extreme winds?
- Strong winds in tropical storms are caused by an area of very low pressure at the centre of the storm that creates a big pressure difference to the surrounding area.
- Tropical storms can have wind speeds more than 250 km/h.
- These winds are strong enough to damage or destroy buildings and plants, and cause loose objects to be picked up and transported.
How can tropical storms cause extreme rain?
- Extremely high amounts of precipitation can fall rapidly in tropical storms.
- Caused by large amounts of warm, moist air being sucked towards the centre of the storm due to the difference in pressure.
- As this happens, the air rises, cools and condenses, causing rain.
- There can be enough rain to cause flooding and mudslides.
Describe the distribution and frequency of tropica
Frequency of tropical storm changes, but distribution doesn't.
- Most tropical storms occur between 5 degrees - 30 degrees N and S - any further, the water isn't warm enough.
- Majority of storms occur in the Northern hemisphere (especially over the Pacific), in late summer and autumn, when sea temperatures are highest.
- Number of tropical storms varies each year.
- In Atlantic, number of tropical storms has increased since 1984 - no overall trend over the last 130 years.
Describe the normal conditions in the Pacific Ocea
LOW PRESSURE HIGH PRESSURE
AUSTRALIA SOUTH AMERICA
- Remember: trade winds blow from EAST to WEST.
- Low pressure: warm air rises, causing rain and thunderstorms. When warm air rises and condenses, the rain clouds become saturated.
- High pressure: air sinks, no air is rising and condensing to form clouds, causing clear skies and dry weather.
- When the trade winds blow from EAST to WEST, the water is pushed to the WEST, in the same direction as the trade winds.
- This means that the warm, surface water is pushed towards the WEST. The colder water from the bottom of the Pacific rises up and replaces the warm water that is being pushed to the WEST. This is called Upwelling.
Describe the La Niña event.
- When the normal conditions become more extreme.
- Trade winds blow to the west more strongly, and more cold water rises in the eastern Pacific.
- It causes more heavy rainfall and floods in the west, and less rainfall and droughts in the east.
- La Niña events occur every 2-7 years.
Describe the El Niño events.
HIGH PRESSURE LOW PRESSURE
AUSTRALIA SOUTH AMERICA
- High pressure: leads to unusually dry weather. Can cause droughts - there can be much less rainfall in places like Australia.
- Low pressure: unusually wet weather. Can cause serious floods in places that usually don't recieve much rain.
Occur every 3-4 years on average, last for 9 - 12 months.
What is drought?
- When conditions are drier than normal.
- A drought is a long period when rainfall is below average.
- As a result of droughts, water supplies become depleted because people continue to use them and they aren't replenished by the rainfall.
- Droughts = high temperatures = increased rate of evaporation = water supplies become depleted faster.
- Length can vary for eg. the worst drought in Britain lasted 16 months.
Describe how El Niño and La Niña cause droughts.
- Changes in atmospheric circulation can mean that places could experience droughts for months or years.
- For eg. the drought in Australia in 2000s was made worse by an El Niño event in 2002.
- Changes in the atmospheric circulation can also make annual rains fall (eg. monsoon rains don't come when they normally do in places like India).
- Droughts are also caused when high pressure weather systems (anticyclones) block depressions (weather systems that cause rain) and this can happen in the UK.
Describe the distribution and frequency of drought
Frequency has not changed much but the distribution has.
- Areas most at risk from drought are places like Australia and parts of North America.
- Location varies.
- Since 1950s, there has been an increase in droughts in places like Africa and Asia and a decrease in droughts in places like Russia and Americas.
- Has changed but not by much since 1950.
- Some scientists suggest that droughts may become more frequent and more severe in the future due to climate change.
CASE STUDY - Introduce Hurricane Katrina.
- Struck Mississippi and Louisiana, south-east USA in 29th August 2005.
What caused Hurricane Katrina to form?
- Louisiana and Mississippi are located in the Gulf of Mexico, where sea temperatures are 27ºC or warmer which encourages tropical storms to form.
- A storm formed 200 miles south-east of the Bahamas on the 23rd of August, it moved north-west past Florida and into the Gulf of Mexico.
- As it travelled over the warm water of the Gulf of Mexcio, it became stronger.
- As the water was warm, it affected the air, causing it to become warm. Warm air rised and condensed to form clouds, causing extreme precipitation.
- Throughout the process of
- On the morning of 29th August, it struck land. Winds: 200 km/h. Rainfall: 200-250 mm. IN LOUISIANA.
- In Mississippi: storm surge of up to 8.5 m.
Describe four consequences to Hurricane Katrina.
- More than 1800 people were killed.
- 300,000 houses were destroyed and hundreds and thousands of people were made homeless.
- Large areas were flooded, including 80% of New Orleans.
- 230,000 jobs were lost from damaged businesses.
Describe four responses to Hurricane Katrina.
- 70-80% of New Orleans residents were evacuated before the hurricane reached land.
- Repaired and improved flood defenses for New Orleans costing 14.5 billion dollars were completed in 2013.
- US government provided over 16 billion dollars for the rebuilding of homes, and provided funds to repair other essential infrastructure.
- Charities collected donations and provided aid, including millions of hot meals.
How do tropical storms cause storm surges?
- Tropical storms can cause storm surges as strong winds push water towards the shore, causing the water level to rise.
- If the storm surge coincides with a high tide, flood defences can easily be breached.
CASE STUDY - Heat wave
- A heat wave is a long period during which the temperature is much higher than normal.
- Conditions are different in different places.
- Heat waves are caused when anticyclones - areas of high pressure - stay in the same place for some time.
- Anticyclones can last for a long period of time, leading to a heat waes, like the European Heat Wae that affected the UK in August 2003.
Describe the causes of the 2003 Heat Wave.
- An anticyclone was situated over western Europe for most of August.
- Air moves clockwise around an anticyclone, so hot, dry air from the centre of the continent was brought to western Europe.
- This meant that temperatures in the UK were higher than normal and rainfall was lower than normal.
- The anticyclones blocked low pressure systems/depressions that would normally bring cooler, rainier conditions from the Atlantic Ocean.
Describe four consequences to the 2003 Heat Wave.
- People suffered from heat stroke, dehydration, sunburn and breathing problems caused by air pollution. Some people drowned when cooling off in rivers, lakes and pools.
- Around 2000 people died in the UK from causes linked to the Heat Wave.
- Livestock died due to the heat, and crop yields were lower due to the lack of water.
- Trains were disrupted by rails buckling in the heat and some roads melted, which caused delay.
Describe the structure of the Earth.
- Centre = has an inner and outer core. The inner core is a ball of solid iron and nickel. The outer core is liquid.
- Around core = mantle, which is semi-molten rock that moves slowly.
- The outer layer of the Earth = crust.
- The crust = divided into tectonic plates that move on the mantle.
Compare continental and oceanic crust.
Continental crust is thicker and less dense whereas oceanic is thinner and more dense. Continental crust is between 25km - 100km thick and is made of granite. Oceanic crust is between 5km - 10km and is made of basalt.
Define plate boundary/margin.
Where two plate boundaries meet.
How do convection currents cause plates to move?
- The lower parts of the mantle are sometimes hotter than the upper parts.
- When these lower parts heat up they become less dense and slowly rise.
- As they move towards the top of the mantle, they cool down, become more dense and then slowly sink.
- These circular movements are called convection currents and they cause plate tectonics to move.
Describe what occurs at destructive boundaries.
An oceanic and continental crust meet. As the oceanic crust is more dense, when the two plates meet, the oceanic crust subducts into the mantle. Due to the pressure of the oceanic crust subducting, and the water that enters that mantle which releases steam, the magma rises through the cracks in the Earth's surface called vents. Over time, a composite volcano forms.
- Made up of ash and lava that has erupted, cooled and hardened into layers.
- The lava is usually thick and flows slowly.
- This then hardens quickly to form a steep sided volcano.
- Are formed from destructive plate boundaries.
- There is usually a pyroclastic flow, meaning that the lava contains gas, ash and rock.
Earthquakes can also occur at destructive plate boundaries as tension builds up when one of the plates get stuck as it is moving into the mantle.
An example of a destructive plate boundary is the Pacific plate (oceanic) and the Eurasian plate (continental).
Describe what occurs at constructive plate boundar
When two plates are moving away from each other, magma (molten rock) rises from the mantle to fill the gap. Eventually, the gap cools which creates new crust. This forms a shield volcano.
Shield volcanoes have:
- Shield volcanoes have runny lava as it is made up of basalt and less silica.
- Shield volcanoes have a wide base with gentle sides, which is also a result of the runny lava because it would need to travel a long distance before solidifying and cooling.
- Unlike composite volcanoes, the lava is pure lava and aren't very explosive.
- They are formed at hotspots or constructive plate boundaries.
Earthquakes are also formed from constructive plate boundaries. This is because tension builds up along the cracks within the plates as they move away from each other.
An example of constructive plate boundary: the Eurasian plate and the North American plate.
Describe what occurs at conservative boundaries.
When two plates are moving sideways past each other, or are moving in the same direction but at different speeds. Here, crust isn't created or destroyed, and as a result of the friction earthquakes occur. Earthquakes also form because of the tension that builds up when the plates that are grinding past each other get stuck, and when they try to get unstuck, the jerking movement causes the earthquake.
For example: the Pacific plate and the North American plate.
Describe what occurs at collision boundaries.
When two equally dense plates (2 continental plates) push against each other and pushes up. No plate enters the mantle, instead both plates are folded and pushed upwards, creating fold mountains. Earthquakes also form as tension builds as the plates are pushed together.
For example: the Eurasian and Indian plates colliding to form the Himalayas.
How can earthquakes occur at each plate boundary?
- Tension builds up at all plate boundaries.
- The plates eventually jerk past each other, sending out shockwaves (vibrations).
- These vibrations cause the earthquake.
- The shock waves spread out from the focus, the point in the Earth where the earthquake starts.
- Shallow focus = focus is closer to the surface of the Earth which means that there is more damage. They are caused by tectonic plates moving at or near the surface. They usually have a focus between 0-70 km below the Earth's surface.
- Deep focus = focus is further away from the surface of the Earth, which means that the shock waves travels a long distance before reaching the surface of the Earth. The seismic waves have to travel more rock to reach the surface, which reduces their power (and the amount of shaking) when they reach the surface. They are caused by crust that has previously been subducted into the mantle moving towards the centre of the Earth, heating up or decomposing. They have a focus between 70-700 km.
- The epicentre = the point on the Earth's surface directly above the focus.
What are hotspots?
- An area on the Earth's crust that is hotter than the surrounding area.
- They occur when a plume of hot magma from the mantle moves towards the surface, causing an unusually large flow of heat from the mantle to the crust.
- Sometimes, the magma can break through the crust and reach the surface. When this happens, there is an eruption and a volcano forms.
- Hotspots can be found in oceanic or continental crust, and can be near or far from the plate boundary.
- Hotspots remain stationary over time, but the crust moves above them, this creates chains of volcanic islands with shield volcanoes.
- For example: Hawaii is a chain of volcanic islands in the middle of the Pacific plate.
CASE STUDY - Introduce Haiti.
- The Haiti earthquake occured on 12th January 2010.
- Haiti is located in the Carribean.
- Haiti covers 27,560 square kilometers of land.
What caused the Haiti earthquake to form?
- Haiti is an LIDC.
- Haiti had a weak government and very little money.
- There were very few earthquake resistive buildings, and the buildings that were already there were poorly built.
- Haiti is described as the poorest country in the Western Hemisphere. It's GDP is 143rd out of 227 countries.
- The Port-au-Prince was home to more than 2.5 million people.
- The focus was 13 km underground, and the epicentre was 25 km away from the Port-au-Prince.
- The earthquake occured at a conservative plate boundary between the Carribean and the north American plates.
What are the consequences of the Haiti earthquake?
- About 220,000 people died.
- 300,000 people were injured.
- Eight hospitals or health centres collapsed, or many were badly damaged.
- 100,000 houses were destroyed.
- 200,000 houses were damaged.
- 1.3 million Haitians were displaced.
- Haiti would be dependent on overseas to help it recover.
- There were outbreaks of cholera.
- There were many dead bodies in the rubble which created health hazards.
What are the responses to the Haiti earthquake?
- Over 2 million Haitians were left without water and flood. Looting became a serious problem.
- Field hospitals were set up and helicopters flew around to help wounded people.
- Bottled water and purification tablets were given to survivors.
- Displaced people moved into tents and temporary shelters and there were concerns that there were outbreaks of disease.
- New homes would need to be built to a higher standard, costing billions of dollars.
Early warning systems for earthquakes...
- Early warning systems for earthquakes - seismometers and lasers can be used to monitor earth's movement. Early warning systems mean that warnings can be communicated quickly and automatically to people and control systems when shaking is detected using the internet, SMS networks and sirens.
- This is helpful because:
- people can get under cover
- people doing delicate or dangerous jobs can stop and make the situation safe
- utilities like gas can be turned off which would prevent fires and leaks
- trains can start slowing down, making derailments due to damaged track less likely.
Predicting and monitoring volcanoes...
- Predicting and monitoring volcanoes - predicting volcanoes give people time to evacuate which would reduce the number of deaths and injuries. Seismometers, lasers and other sensors can detect indications that an eruption is likely, such as tiny earthquakes, escaping gas and changes in the shape of the volcano (eg. bulges in the land where magma has built up under it).
- Predicting volcanoes can help authorities respond appropriately: evacuation zones can be extended if eruption becomes more violent, ash clouds that can damage aircraft can be tracked, causing them to be diverted or cancelled so passengers aren't at risk and if ash and poisonous gases spread, authorities can warn people to put gas masks.
- Buildings can be designed to withstand earthquakes eg. by using materials like reinforced concrete or building special foundations that absorb an earthquake's energy.
- Existing buildings and bridges can be strengthened (eg. by wrapping pillars in steel frames).
- Pipelines (eg. for gas and water) can be designed to flex and not break during earthquakes. This helps to prevent deaths and damage to property caused by flooding and fires.
Define climate change.
Climate change is any significant change in the Earth's climate over a long period. The climate is constantly changing.
What is the Quaternary period?
- The Quaternary period is the most recent geological time period, spanning from about 2.6 million years ago to the present day.
- In the period before the Quaternary, the Earth's climate was warmer and quite stable, things have changed.
- During the Quaternary, global temperatures has shifted between cold glacial periods that last for around 100,000 years and the warmer interglacial periods that last for around 10,000 years.
- The last glacial period ended around 15,000 years ago, since then, the climate has been warming.
What is global warming?
- The term used to describe the sharp rise in global temperatures over the last century, it is a type of climate change.
How do ice cores provide evidence for climate chan
- Ice sheets are made up of layers of ice - one layer forms 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.
- One ice core from Antarctica shows the temperature changes over the last 400,000 years.
- Data collected can be very detailed and reliable.
How can diaries and paintings provide evidence?
- Historical diaries can show what the climate was like in the past, eg. by giving the number of days of rain or snow and the dates of harvests (eg. an early harvest = warm weather).
- Paintings of fairs and markets on frozen rivers show that winters in Europe were regularly more colder 500 years ago then they are now.
- However, diaries and paintings aren't very reliable as they just give one person's viewpoint.
How can sea ice positions prove climate change occ
- Sea ice forms around the poles in winter when ocean temperatures fall below -1.8 degrees celsius and melts during late summer where it is warmer.
- By observing the maximum and minimum extent of sea ice each year, scientists can tell how ocean temperatures are changing.
- Data is very reliable, but accurate records don't go very far back.
How does temperature data prove climate change?
- Since the 1850s, global temperatures have been measured accurately using thermometers.
- This gives reliable but short-term record of temperature changes.
- However, weather stations are not evenly distributed across the world - data from some areas is patchy.
Describe the Milankovitch cycle.
Milankovitch cycles are variations in the way the Earth moves around the sun.
- Stretch - the path of the Earth's orbit around the sun changes from an almost perfect circle to an ellipse and back again every 96,000 years.
- Tilt - the Earth is tilted at an angle as it orbits the Sun. This tilt/axis changes over a cycle of 41,000 years.
- Wobble - the axis of the Earth wobbles like a spinning top on a cycle of about 22,000 years.
These cycles affect how far the Earth is from the sun, and the angle that the sun's rays hit the Earth. This changes the amount of solar radiation the Earth recieves. If the Earth receives more energy, it gets warmer.
Tilt and wobble also affect how much solar radiation is received at different latitudes at different times of year.
Orbital changes may have caused the glacial and interglacial cycles of the Quaternary period.
- Sunspots are cooler areas of the Sun's surface that are visible as dark patches.
- They increase the Sun's output of energy.
- Sunspots come and go in cycles of about 11 years.
- There may also be longer sunspot cycles of several hundres or thousands of years.
- Periods are when there are very few sunspots and solar output is reduced may cause the Earth's climate to become cooler in some areas.
- Most scientists think that changes in solar output don't have a major effect on global climate change.
- A volcanic eruption could affect world climate patterns as when volcanoes erupt, they emmit large quantities of ash and sulfur dioxide.
- The ash particles block out the sun's rays which could cause global dimming.
- This is because wen the sun's rays are blocked, the Earth begins to cool.
- This is called a Volcanic winter and it is a short term consequence to climate change.
- On the other hand, sulfur dioxide reflects the sun's rays back into space.
- This is a long term consequence of climate change.
- The particles coud affect climate change as the wind could transport these particles to other parts of the world, affecting world global patterns.
Describe the natural greenhouse effect.
- The natural greenhouse effect is essential for keeping our planet warm.
- The temperature of the Earth is a balance between the heat it gets from the sun and the heat it loses to space.
- Gases in the atmosphere naturally act like an insulating layer, trapping outgoing heat, helping to keep the Earth at the right temperature.
- This is called the greenhouse affect.
- Gases that trap heat are called greenhouse gases, the include carbon dioxide and methane.
What is the enhanced greenhouse effect?
- Human activities causing global warming, making the greenhouse effect stronger, heating up the Earth at a faster rate.
4 human activities increasing global warming...
- Farming - farming of livestock produces a lot of methane, rice paddies contribute to global warming because flooded fields emit methane.
- Burning fossil fuels - carbon dioxide is released into the atmosphere when fossil fuels are burnt eg. in thermal power stations or in cars.
- Cement production - cement is made from limestone, which contains carbon. When cement is produced, carbon dioxide is released into the atmosphere.
- Deforestation - plants remove carbon dioxide from the atmosphere and convert it into organic matter for photosynthesis. When trees and plants are removed, they stop taking in carbon dioxide. Carbon dioxide is also released into the atmosphere when trees are burnt as fuel or to make way for agriculture.
Describe 3 environmental impacts of global climate
- Temperatures are expected to rise by 0.3-4.8 degrees celsius between 2005 and 2100.
- Sea ice is shrinking which causes sea level rise and the loss of polar habitats.
- Percipitation patterns are changing, global warming is affecting how much rain areas receive.
Describe 3 economic impacts of global climate chan
- Climate change means more extreme weather, more money is spent on predicting extreme weather events, reducing impacts and rebuilding after them.
- Water shortages may affect our ability to generate power - hydroelectric power and thermal power stations require a lot of water.
- Climate change affects farming: some crops like maize crops which have gotten smaller, have suffered from climate change, but some farmers in high latitude countries are finding that crops benefit from warmer conditions.
Describe 3 social impacts of global climate change
- In some countries, reduced rainfall means that there is an increased threat from wildfires which not only destroys homes, but puts people at risk.
- Some areas can become so hot and dry that they're difficult or impossible to inhabit. Low-lying coastal areas could be lost to the sea or flood so often that they also become impossible to inhabit. This could lead to migration and overcrowding in other areas.
- Some areas are struggling to supply enough water for their residents due to problems with water availability caused by changing rainfall patterns. This could lead to political tensions, especially where rivers cross borders.
Environmental impacts of UK climate change.
- Climate - average temperatures in southern England are expected to increase by 3.9 degrees celsius by 2080, winter rainfall = increase by 16 % -> western UK, summer rainfall = decrease -> southern UK.
- Sea level rise - sea level is expected to rise from 12 cm - 76 cm by 2095, loss of habitat.
- Wildlife - can upset balance of natural ecosystems and can lead to species extinction due to the changed migration patterns and from species moving.
Economic impacts of UK climate change.
- Tourism - more people decide to stay at home due to the warm weather, some places it could lead to decline like skiing in Cairngorms.
- Agriculture - temperature increase = longer growing seasons = can increase productivity of some crops. New crops adapted to warmer weather can be grown in southern England, however, reduced rainfall and droughts could increase the need for irrigation and water storage schemes.
- Fishing - fishing infrastructure at risk from storm damage, fishermen's livelihood is affect by changing fish populations.
Social impacts of UK climate change.
- Health - deaths from cold related illnesses may decrease, but health services may need to treat heat-related illnesses like heat exhaustion.
- Water shortages - drier summers will affect water availability, particularly in areas of south east England where population density is increasing.
- Floods - as a result of increased rainfall and sea level rise might damage homes and businesses, especially those on estuaries and low lying areas near the cost.
What is a landscape?
- Landscapes are made up of all the visible features of an area of land.
- A landscape with more physical features, such as mountains or forests is described as a natural landscape.
- A lanscape with more human features, like a town or a city, is described as a built landscape.
Describe the upland areas in the UK.
- Usually north and west of the UK.
- Made up of harder rocks that resist erosion such as slate, granite and some limestones.
- Many glaciated landscapes.
- Gradient of land is often steep.
- Cooler and wetter climate.
- Harsh climate and thin soils allow rough vegetation to thrive and some upland areas are used for forestry.
- Land uses: sheep farming, quarrying and tourism.
Describe the lowland areas in the UK.
- Usually south and east.
- Made of softer rock like chalk, clay and some sandstones.
- Landscape is generally flatter with gently rolling hills.
- Warmer and drier climate.
- Vegetation grows easily in the more fertile soils and includes grassy meadows and deciduous forests.
- Land use: quarrying and tourism, as well as dairy and arable farming (growing crops).
- Most urban areas and industries are located in lowland areas.
Describe the glaciated landscapes in the UK.
- During the last glacial period, ice covered the UK as far as south, so glaciated landscapes are mostly found in upland areas in the north-west of the UK.
- Ice is very powerful, so it was able to erode the landscape, carving out valleys. It also deposited lots of material as it melted.
- Landscapes formed by glacial meltwater and deposits extend south.
What are the three ways rock is broken down?
- Mechanical weathering - breakdown of rock without changing the chemical composition, the main type of mechanical weathering in the UK is freeze-thaw weathering. It happens when the temperature alternates above and below 0 degrees celsius (the freezing point of water). Water gets into the rock that has cracks like granite. When the water feezes, it expands, which puts pressure on the rock. When the water thaws, it contracts, which releases the pressure on the rock. Repeated freezing and thawing widens the rock, causing the rock to break up. Salt weathering is caused by the build up of salt crystals deposited in cracks by water.
- Chemical weathering - breakdown of rock by changing chemical compostition. Carbonation weathering is a type of chemical weathering that happens in warm and wet conditions. Rainwater has carbon dioxide dissolved in it, making it a weak carbonic acid. Carbonic acid reacts with the rock that contains calcium carbonate, so the rocks are dissolved by the rainwater.
- Biological weathering - the break down of rocks by living things eg. plant roots break down rocks by growing into cracks on their surfaces and pushing them apart.
What is mass movement?
- When materials fall down a slope.
- Mass movement is the shifting of rocks and loose materials down a slope.
- It occurs when the force of gravity acting on a slope is greater than the force supporting it.
- Mass movement causes costs to retreat rapidly.
- They're more likely to happen when the material is full of water - it acts as a lubricant and makes the material heavier.
- Undercutting of a slope by erosion will increase the chance of mass movement.
- Slides: material shifts in a straight line.
- Slumps: material shifts with a rotation.
Describe the four processes of erosion.
- Hydraulic action - along coasts waves crash against rock and compress the air in the cracks. This puts pressure on the rock, and repeated compression widens the cracks and makes bits of rock break off. In rivers, the force of the water breaks rock particles away from the river channel.
- Abrasion - eroded particles in the water scrape and rub against rock in the sea bed, cliffs or river chanel, removing small pieces and wearing them away. Most erosion in rivers happens by abrasion.
- Attrition - eroded particles in the water smash into each other and break them into smaller fragments. Their edges also get rounded off as they rub together. The further material travels, the more eroded it gets.
- Solution - dissolved carbon dioxide makes river and sea water slightly acidic. The acid reacts chemically with some rocks like chalk ad limestone, dissolving them.
What are the four main processes of transportation
- Traction - large particles like boulders are pushed along the river bed of sea floor by the force of the water.
- Suspension - small particles like silt and clay are carried along by the water.
- Saltation - pebble-sized particles are bounced along the riverbed or sea floor by the force of the water.
- Solution - soluble materials dissolve in the water and are carried along.
What are the two types of deposition?
- Coastal deposition:
- Waves that deposit more material than they erode are called constructie waves.
- Constructive waves have a low frequency (6-8 waves per minute).
- They are low and long.
- The swash (the movement of water up the beach) is powerful and it carries materials up the coast. The backwash (the movement of water down the beach) is weaker and it doesn't take a lot of materials back down the coast. This means that there is lots of deposition and very little erosion.
- The amount of material that is deposited on an area increases when: there's lots of erosion somewhere else on the coast and there's lots of transportation of material into the area.
- River deposition - few reasons why rivers slow down and deposit material. Deposition occurs when:
- The volume of water in the river falls.
- The amount of eroded material in the water increases.
- The water is shallower.
- The river reaches the sea or a lake at its mouth.
How are headlands and bays formed?
- Headlands and bays are formed where there are alternating bands of resistant and less reistant rock along the coast.
- The less resistant rock (clay) is eroded quickly and this forms a bay with gentle slopes and they are usually beaches.
- The resistant rock (chalk) is eroded more slowly and it's left jutting out, forming a headland with steep sides.
What happens when headlands are eroded?
- Headlands are usually made of resistant rocks which have weaknesses such as cracks.
- Waves crash into the headlands and enlarge the cracks - hydraulic action and abrasion.
- Repeated erosion and enlargement of cracks causes a cave to form.
- Continued erosion deepens the cave until there is a break through to the other side, forming an arch.
- Erosion continues to wear away the rock supporting the arch, until it eventually collapses.
- This forms a stack - an isolated rock that's separate from the headland.
How are beaches formed?
- From deposition
- They are found on coasts between the high water mark (the highest point on the land the sea level gets to) and the low water mark (the lowest point on the land the sea level gets to).
- They're formed by constructive waves depositing sediments like sand and shingle.
- Sand beaches - flat and wide, sand particles are small and the weak backwash can move them back down the beach, creating a long, gentle slope.
- Shingle - steep and narrow - shingle particles are large and the weak backwash can't move them back down the beach. The shingle particles build up and creates a steep slope.
What does longshore drift form?
- It can form spits at bends in the coastline.
- Spits are just beaches that stick out into the sea - they're to the coast at one end, spits form at sharp bends in the coastline, eg. at river mouths.
- Spits are formed from longshore drift - a process that transports material along the coast:
- Waves follow the direction of the prevailing wind. They usually hit the coastline at an oblique angle (any angle that isn't a right angle). The swash carries material up the beach, in the same direction as the waves. The backwash then carries the material down the beach at right angles, back towards the sea. Over time, the material zigzags along the coast.
- Longshore drift transports sand and shingle past the bend and deposits it in the sea.
- Strong winds and waves can curve the end of the spit, forming a recurved end.
- The sheltered area behind the spit is protected from waves - lots of material accumulates in this area, meaning that plants can grow there.
- Over time, the sheltered area can become a mud flat or a salt marsh.
CASE STUDY - Dorset coast introduction.
- Located on the south coast of England.
- Called the Jurassic coast because it has lots of fossils dating from the Jurassic period.
- Lots of people come to the area to hunt for fossils, and it's an important location for scientists studying geology.
- Variety of coastal landforms making it a popular tourist destination.
Describe the variety of different landforms at Dor
- Durdle door - arch, hard limestone headland. Arch is gradually broken down by mechanical, chemical and biological weathering.
- The Foreland, Old Harry and his Wife - in between two areas of softer rock made from a band of harder rock (chalk). An arch at the end of the headland has collapsed to form a stack called Old Harry and a stump (a collapsed stack) called Old Harry's Wife. Salt and carbonation weathering, along with erosion. are gradually wearing down Old Harry and his Wife. The vegetation growing on the top also breaks up the rock through biological weathering.
- Chesil beach - tombolo (type of spit that extends out to an island). It joins the Isle of Portland to the main land. Formed by LSD. Behind Chesil beach is a shallow lagoon called The Fleet Lagoon.
- Lulworth Cove - small bay formed after a gap was eroded in a band of limestone. Behind the limestone is a band of clay. They clay is softer so it has been eroded and transported away, forming the bay. The limestone cliffs forming the back wall of the bay are vulnerable to mass movement, can experience small slides and slumps.
- Swanage Bay - cliffs backing are made of clay, a soft rock. Towards northern bay, cliffs are covered in vegetation, stabilising them and protecting them from weathering. Elsewhere, the cliffs are not stabilised by vegetation. so wet weather weakens them and can cause slumps. LSD carries material (mainly gravel) from the south to the north of the beach in the bay. Overall, erosion is the dominant process in the bay - the beach has been losing material for decades.
How has temperature affected processes?
- The Dorset coast has warm, dry summers (around 21 degrees celsius in July) and mild and wet winters (3 degrees celsius in January).
- Salt weathering is the dominant form of mechanical weathering, particularly in summer. The warm temperatures cause sea water to evaporate from rocks quickly, leaving a build up of salt crsytals in tiny cracks in the rock.
- The mild winters mean mean that freeze-thaw weathering is less common because it's usually not cold enough for ice to form.
How has wind affected processes?
- The Dorset coast's location means that it's exposed to prevailing winds from the south-west.
- These prevailing winds can bring storms to the UK from the Atlantic Ocean.
- Storms bring high energy, destructie waves which increases erosion of the cliffs.
- Hydraulic action and abrasion both increase during a storm and erode the base of the cliffs.
- This makes the cliffs unstable, making mass movement more likely to happen.
How has rainfall affected processes?
- The Dorset coast receives low amounts of rainfall annually, but can experience very wet winters, with rainfall heaviest during storm periods.
- Soils and rocks become heavier when they're saturated, which can make them more prone to mass movement.
- In January 2016, intense rainfall combined with high-energy waves during Storm Frank to cause the collapse of cliffs between Burton Bradstock and West Bay.
How does geology affect processes?
- The coastline is made from alternating layers of hard rock and soft rock. The rocks have been eroded at different rates, which has caused the area's coastal landforms.
- Soft rock like standstone and clay are easily eroded by hydraulic action and abrasion.
- The harder chalk and limestone cliffs are weathered and eroded more slowly, meaning that they stick out into the sea as exposed headlands. Chalk and limestone are vulnerable to erosion by solution, where the sea water chemically reacts with the rock, causing it to dissolve.
- Weathering tends to happen gradually and cause small changes. Erosion can happen more suddenly on a much larger scale. A single storm can cause large amounts of erosion along a big stretch of the coast.
What occurs when climate, geology and weather inte
- A combination of climatic and geological factors that affect how erosion and weathering shape the landscape.
- Lots of rain makes chalk and limestone vulnerable to carbonation weathering because the rainwater is slightly acidic.
- Prolonged heavy rain causes clay to become heavier, softer and more slippery, making mass movement more likely. During the winter, when there is more rainfall, there are often slides and slumps on the clay cliffs.
UK coastal management - Groynes.
- Groynes are wooden or stone fenes that are built at right angles to the coast.
- They trap material transported by LSD. This creates wider beaches which slow the waves, giving a greater protection from erosion.
- New timber groynes were put in place along Swanage beach in 2005-6. They've helped to stop the loss of beach material.
- However, by stopping beach material from moving along the coast, they've starved areas further down the coast of sediment, making them narrower.
- Narrow beaches don't protect the coast as well, so there may be more erosion.
How are industry and tourism shaping Dorset?
- A lot of quarrying has taken place along the coast because limestone is a valuable building stone.
- There are a large number of quarries on the Isle of Portland and to the west of Chesil Beach.
- Quarries expose large areas of rock making them vulnerable to chemical weathering and erosion.
- Up until the 1960s, gravel was removed from Chesil Beach for use in the construction industry.
- Material was removed from the beach much more quickly than the sea could replenish it, so this began to damage the landform.
- The Dorset coast attracts large numbers of tourists every year. Coastal footpaths run along the cliff tops, and are gradually worn down as people repeatedly walk on them.
- Vegetation along the cliff top may be trampled and worn away by repeated use of the footpaths.
- This can expose underlying soil and rock to weathering and erosion by wind and rain.
What is a river basin?
- An area of land surrounding the river, where any rain falling on the land eventually makes its way into that river. This is also called the river's catchment.
- They are separated by a boundary called a watershed. They are ridges of high land - water falling either side of these ridges will go into different river basins.
- A tributary is a smaller river (eg. a stream) that joins a main river.
- The source is where a river starts, usually in an upland area (eg. mountains).
- The mouth is where a river flows into the sea or a lake.
- The path of a river as it flows downhill is called its course.
- Rivers have upper (closest to the source) , mddle and lower courses (closest to the mouth).
- Rivers form channels and valleys as they flow downhill.
- They erode the landscape - wear it down, then transport the materials somewhere else where it is deposited.
- The shape of the valley and channel changes along the river depending on whether erosion or deposition is the dominant process.
- Confluence = where two tributaries meet.
What river landforms are formed at each course?
- V-shaped valleys
- Ox-bow lake
How are V-Shaped valleys formed?
- By vertical erosion in the upper course.
- In the upper course: fast flowing water, heavy rain and high turbulence causes loose rough particles and boulders to be transported by the river and scraped along the river bed.
- This causes downwards erosion of the river channel by abrasion.
- The valley sides are exposed to weathering (freeze thaw).
- The weathered material that falls down the valley sides into the river channel causes further erosion by abrasion.
- The river doesn't have enough energy to erode sideways (laterally), so vertical erosion of the river bed is dominant, which deepens the river valley and forms a steep-sided V-shaped valley.
How are waterfalls and gorges formed?
- Waterfalls form where a river flows over an area of hard rock followed by an area of soft rock.
- The softer rock is eroded by hydraulic action and abrasion more than the softer rock, creating a step in the river.
- As water goes over the step, it erodes more and more of the softer rock.
- A steep drop is eventually created, which is a waterfall.
- The hard rock is eventually undercut by erosion. It become unsupported and collapses.
- The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion. This creates a deep plunge pool.
- Over time, more undercutting causes more collapses. The waterfall will retreat (move back up the channel), leaving behind a steep-sided gorge.
What are meanders formed from?
- Meanders are formed by erosion and deposition
- The current (flow of river) is fastest outside the bend because the river is deeper and there is less friction to slow the water down.
- So more erosion takes place outside the bend, forming river cliffs.
- The current is slower inside the bend because the river channel is shallower and there is more friction to slow the water down.
- So eroded material is deposited on the inside of the bend, forming slip-off slopes.
How are Ox-Bow lakes formed?
- They are formed from Meanders.
- Erosion causes the outside bends to get closer until there is only a small bit of land left between the bends/necks.
- The river breaks through the land, usually during a flood and the river flows along the shortest course.
- Deposition eventually cuts off the meander forming an ox-bow lake.
What are Floodplains?
- They are flat areas of land that flood.
- The floodplain is the wide valley floor on either side of a river which occasionally gets flooded.
- When a river floods into the floodplain, the water slows down and deposits the eroded material that it's transporting.
- This builds up the floodplain, making it higher.
- Meanders migrate across the floodplain, making it wider.
- Meanders also migrate downstream, flattening out the valley floor.
- The deposition that happens on the slip-off slopes of meanders also builds up the floodplain.
What are levees?
- Natural embankments (raised bits) along the edges of the river channel.
- During a flood, eroded material is deposited over the whole floodplain.
- The heaviest material is deposited closer to the river channel, because it gets dropped first when the river slows down.
- Over time, the deposited material builds up, creating levees along the edges of the channel, eg. along the Yellow River (Huang He River) in China.
CASE STUDY - Introduce the Eden Basin.
- The Eden Basin is in north-west England, between the mountains of the Lake District and Pennines.
- The river Eden's source is in the Pennine Hills in south Cumbria.
- It flows northwest through Appleby-in-Westmorland and Carlisle.
- Its mouth is in the Solway Firth at the Scottish border.
- The river basin is a largely rural area, which many scenic landscapes that are popular with tourists.
- There are a variety of river landforms.
Describe the variety of landforms in the Eden Basi
- Waterfalls - Hell Gill Force, near source of river Eden. It is formed when there is a change in the rock type from hard limestone to softer sandstone. The water has eroded the soft rock, forming a step in the river channel. Below the waterfall, there is a steep-sided gorge, left behind as the waterfall retreats up the valley.
- Meanders - As more tributaries join the river Eden, the river gets bigger. This gives it more power to erode the channel sideways. In the lower course, the river valley becomes wider and flatter, and meanders form on the valley floor, eg. near Salkeld. As these meanders have grown, some hae been cut off to form ox-bow lakes, eg. where Briggle Beck joins the Eden near Salkeld.
- V-shaped valleys - Many streams flow down the steep slopes of the hillsides at the edge of the basin from about 600 m above sea level. Weathering by freeze-thaw, transportation by traction and erosion by abrasion have carved out steep-sided v-shaped alleys, eg. in the north-east Lake District.
- Floodplains - Carlisle is built on the floodplain of the river Eden. Here, the land is low-lying and flatter, less than 100 m above sea level. As meanders have migrated across the valley floor, the floodplain has become wider. Sediment has also been deposited when the river has flooded, building up the floodplain.
How do climate and weather affect Eden Basin?
- Despite the mild winters, temmperatures can be much colder on higher ground, such as the land around the sources of the river Eden. In winter, this higher ground can regularly freeze.
- During these cold periods, freeze-thaw weathering can slowly break up the exposed rock of the valley sides in the upper course of the river. If the valley sides are weakened, sudden mass movement such as landslides become more likely.
- Material from landslides is added to the river's load (the rocks, stones and sediment transported by the river), increasing the erosive power of the river through abrasion.
- During periods of intense rainfall, the ground becomes saturated. This makes it heavier and less stable. This can cause the river banks to slide or slump into the river channel.
- Heavy rain can flow quickly over the surface and into the river Eden and its tributaries. This can cause the volume of the water in the river to increase rapidly.
- The high volume of water can increase transportation of material by the river, which can cause more erosion by abrasion - particularly in the upper course of the river.
How does geology affect processes in Eden Basin?
- The harder rocks around the edge of the Eden Basin have remained as high ground as they are more resistant to erosion.
- However, when exposed, limestone is vulnerable to slow carbonation weathering.
- Igneous rocks such as those found in the Eden Basin tend to be impermeable.
- Because water can't soak into the ground, high rainfall causes lots of surface streams to form, which have lots of power to erode vertically, creating steep-sided V-shaped valleys.
- Through the middle and lower courses of the Eden, the river valley is made up of sandstone (a softer rock).
- The river's increasing volume and energy in its lower course mean that there's lots of lateral (sideways) erosion of the sandstone.
- This widens the river channel and forms meanders and steep river-cliffs.
Management schemes in the Eden Basin.
- Flood walls & Embankments - 10 km of raised flood defences (flood walls and embankments) have been built along the Rivers Eden and Caldew in Carlisle. They are designed to contain the water within the river channel, so that the floodplain can be built on. They interrupt the natural processes of the river and can prevent the natural formation of meanders and the deposition of sediment on the floodplain.
- Reservoirs - Castle Carrock beck has been dammed to create a reservoir. These limit the natural flow of water downstream. Material carried by the river is deposited in the reservoir and not along the river's natural course. This can increase erosion downstream and reduce the natural buildup of the floodplain in the lower course of the river.
- Planting trees - Near Dalston, the landscape has been changed by planting 1000 trees to reduce flooding and reduce erosion by stabilising soil. Trees intercept rainfall and reduce surface runoff. This preents rapid increases in the volume of water in the river because it takes longer for water to reach channel. As a result, river has less energy, reducing lateral and vertical erosion, meaning that meanders and ox-bow lakes may be less likely to form.
- Channel Management - in the past, the river landscape in the Eden basin was changed by channell straightening. Many sections of the river were diverted into artificial channels to try to reduce the flooding. Channel straightening meakes water flow more quickly than it naturally would, can cause meanders to form as they normally would, natural river landscape isn't changed. More recently, some areas in Eden basin has been restored to original state by having artificial meanders put in. The meanders slow the river's flow, increasing deposition. Can encourage the development of more meanders, natural build up of floodplain.
Describe 2 human activities affecting processes.
- Deforestation - natural woodland and heathland have been cleared from many upland areas in the Eden basin. This increases surface run-off when it rains, meaning that more water ends up in the river channel more quickly. This increase in volume gives rivers more energy for erosion, and can cause sliding and slumping of the river banks.
- Farming - some upland areas in the Eden basin have been drained of moisture to make it more suitable for farming. This reduces the stability of the soil, meaning that more soil is washed into the river channel by rain. The increased load of the river increases deposition downstream, chaning the floodplain landscape from its natural state.
What does an ecosystem include?
- An ecosystem is a unit that includes all the biotic (living) parts like plants and animals and the abiotic non-living parts like soil and climate in an area.
- The organisms in an ecosystem can be classed as producers, consumers of decomposers.
- A producer is an organism that uses sunlight energy to produce food.
- A consumer is an organism that gets its energy by eating other organisms, it eats producers or other consumers.
- A food chain shows what eats what. A food web shows lots of food chains, how they overlap and how they are interdependent.
- A decomposer is an organism that gets its energy by breaking down dead material, eg. dead producers, dead consumers or fallen leaves. Bacteria and fungi are decomposers. This returns nutrients to the soil, where they can be used by plants.
Global distribution of 6 ecosystems.
- Coral reefs - mostly found 30 degrees N and S of the equator, a few miles off the coast.
- Grassland - two types of grassland. Tropical savannah grasslands are found between the tropics. Temperate grasslands are found at mid-latitudes.
- Temperate forest - found mainly in the mid-latitudes, between the tropics and the polar regions.
- Polar - found areound the north and south poles.
- Hot desert - found between 15 degrees and 35 degrees N and S of the equator.
- Tropical rainforest - found around the equator, between the tropics from 0 degrees to 5 degrees N and S.
Describe polar ecosystems.
- Cold and dry, temperatures are usually less than 10 degrees celsius.
- Rainfall and snowfall is low, no more than 500 mm a year.
- Few plants, some lichens and mosses found on rock, plants grow slowly.
- Some small, short trees and shrubs grow in winter.
- Polar bears
Describe hot deserts.
- Low rainfall, less than 250 mm per year.
- Temperatures are extreme, range from very hot (eg. 45 degrees celsius) to very cold at night (0 degrees celsius).
- Kangaroo rats
Describe savannah grassland.
- Low rainfall (800-900 mm per year), distinct wet and dry seasons.
- Temps are highest around 35 degrees celsius just before the wet season and lowest around 15 degrees celsius just after it.
- Grass scrub
- Acacia tree
- Elephants, giraffes, zebras, antelopes...
Describe temperate grassland.
- Hot summers up to 40 degrees celsius and cold winters up to -40 degrees celsius
- Receive 250-500 mm of precipitation each year.
- Small plants
- Few trees
- Wild horses
- Mole rats
Describe coral reefs.
- Warm areas that receives a lot of sunlight
- Shallow, clear, salty water.
- Sea snakes
Describe temperate forests.
- Mild, wet climate
- Four distinct seasons
- High rainfall, up to 1500 mm per year
- Deciduous forests - broad leaved trees that drop their leaves in autumn.
- Forest floor plants - like bluebells, flower in spring before trees grow leaves and block light.
- Coniferous forests - evergreen trees
- Mammals - foxes, squirrels
- Birds - woodpeckers, cuckoos
- Insects - beetles, moths, mosquitoes
Describe tropical rainforests ecosystems.
- Hot, wet climate.
- Hot - 20-28 degrees celsius
- Rainfall is very high, around 2000 mm, rains everyday
- Evergreen trees
- Dense vegetation
- Lots of epiphytes (plants that grow on other living plants and take nutrients, mositure from air.
- Leaf tailed Geckos
Describe the water cycle in tropical rainforests.
- Water evaporates from water bodies and the land - evaporation is when water is heated by the sun and turns into water vapour. Transpiration is evaporation of water from plants.
- Water vapour is moved by winds.
- The water vapour condenses to form clouds and then falls as rain.
- Water flows from one place to another in various ways, and is also stored in the land.
- Water eventually ends back up in the river or sea, and the cell cycle begins again.
- The sun is usually overhead, so it's always hot - evaporation rates are high.
- High evaporation rates means there's lots of water vapour, so rainfall is high.
- Vegetation is dense, so lots of water is intercepted and stored by the plants.
How are nutrients cycled quickly?
- Trees are evergreen so dead leaves and materials fall all year round.
- The warm, moist climate means that fungi and bacteria decompose the dead organic matter quickly, releasing nutrients into the soil.
- Rainwater soaks into the soil and the nutrients are dissolved into the water.
- Dense vegetation and rapid plant growth mean that the nutrient rich water is rapidly taken up by plants' roots.
Why are rainforest soils low in nutrients?
- Soils in a tropical rainforest are often very deep but they only have a very thin fertile layer and are generally nutrient poor.
- The hot wet climate means that chemical weathering is rapid.
- This means that there is usually a deep layer of soil - the bedrock can be up to 30 m below the surface, lowest layer in the rainforest.
- The trees drop their leaves all year round, so there is a constant supply of dead leaves and twigs falling onto the soil surface, forming a thick leaf layer, the first layer.
- This is quickly broken down to form humus which then gets mixed with the soil. The humus is the second layer.
- The layer of humus is thin because the high density, fast-growing plants quickly absorb the nutrients.
- Nutrients are also leached (washed downwards) through the soil by the heavy rainfall, making the soil nutrient poor.
- Trees and other vegetation hae roots close to the surface, where the nutrients are - so there are lots of roots in the humus layer.
What are rainforests?
- Rainforests are interdependent ecosystems.
- The warm, wet climate means that plants grow quickly - the dense leaf cover protects the forest floor from wind and heavy rainfall, while root systems hold the soil together - this stops it from beind eroded.
- The lack of wind near the forest floor means that many plants there have to rely on bees, butterflies or ther animals for pollination. Symbiotic relationships between plants and animals (where they each depend on each other for survival) are very common in rainforests.
- There are lots of epiphytes (plants that grow on other plants) in rainforests. They get access to light by growing high up on other plants, but they don't have access to the nutrients in the soil - they are dependent on rainfall to provide nutrients and water.
- Changes to the rainforest ecosytem can have knock on effects on the whole ecosystem. For eg. deforestation reduces the amount of carbon dioxide being absorbed from the atmosphere, which adds to the greenhouse effect and changes the climate.
Goods in the tropical rainforest:
High biodiversity (the range of plants and animals found there) means rainforests have a rich source of goods:
- Many products including rubber, coffee, chocolate and medicines are sourced from the rainforest.
- Undiscovered species might lead us to new medicines and other new products.
- Hardwoods eg. mahogany are widely used for furniture and building. Logging of hardwoods can contribute a huge amount to the countries economy.
- Rainforests provide opportunities for farming and mining if the vegetation is cleared.
- This provides lots of jobs and income in many rainforest areas.
Services in the tropical rainforest.
- Home to the highest diversity of animal and plant species on the planet.
- Plants absorb around 0.7 billion tonnes of carbon dioxide from the atmosphere each year, which helps reduce climate change.
- Rainfall is intercepted by the high density of vegetation - this reduces the risk of local flooding because the movement of water to rivers is slowed down.
- Rainforests also help regulate the global water cycle by storing water and releasing it into the atmosphere slowly.
- This can reduce the risk of drought and flooding in areas.
Human activities that have big impacts on rainfore
- Logging - with no trees to hold the soil together, heavy rain washes away the soil (soil erosion). Eroded soil can enter rivers, silting up habitats that fish use for breeding. The removal of trees interrupts the water cycle, leading to dry areas with an increased risk of wildfires, while other areas are likely to flood. Logging requires the building of new roads, which opens up the rainforest to further development.
- Agriculture - land is often cleared using slash-and-burn techniques. Burning vegetation produces carbon dioxide, which adds to the greenhouse effect. Without trees to intercept rainfall, more water reaches the soil. Nutrients are washed away, so soil ferility is reduced - rainforest soils usually lose their fertility in 3-5 years.
- Mineral extraction - mining of precious metals includes heavy machinery and the removal of trees. Toxic chemicals are used to extract and purify the metals washed into streams and rivers, killing wildlife and polluting people's drinking water. There can also be conflict with local people over rights to the land.
- Tourism - may scare wildlife. They may damage vegetation and leave behind lots of littler. If tourism is unregulated, a lack of infrastructure can lead to pollution if waterways. In order to build infrastructure, vegetation must be cleared.
CASE STUDY - Introduce Amazon rainforest.
- North of south America
- Covers 8 million km squared
- Goes through 9 countries: Brazil, Peru, Colombia, Venezuela, Bolivia, Ecuador, Guyana, Suriname and French Guiana.
- Balances the removal of trees to sell with the conservation of the forest as a whole.
- It can involve selective logging, where only some trees are felled so that the forest is able to regenerate or planting new trees to replace the ones that were cut down.
- International agreements try to reduce illegal logging, and promote wood from sustainably managed forests.
- For example, Forest Stewardship Council (FSC) is an organisation that marks sustainably sourced timber products with its logo so that consumers can choose sustainable products.
- Precious Woods Amazon is a logging company operating in Brazil. They place limits on the number of trees that can be cut down, to make sure that the forest can regenerate. They also use a variety of species, so that no species is over-exploited. They are FSC certified.
- Natutama is an organisation in Puerto Narino in Colombia that is working with the local community to protect river species, eg. the Amazon river dolphin.
- It employs local people to teach other people in the community how they can protect endangered river animals and their habitats.
- Local fishermen collect information about the number and distribution of species, and report any illegal hunting or fishing that is taking place.
- The team also organises clean-up days to remove litter from the local rivers.
- Ecotourism is tourism that minimises damage to the environment and benefits the local people.
- Yachana Lodge is an ecotourism project in Ecuador, in a remote area of the Amazon rainforest where local people rely on subsistence farming to provide a living.
- It employs local people, giving them a more reliable income and a better quality of life.
- It also encourages the conservation of the rainforest so that visitors can continue to want to visit,
- Tourists visit in small groups so that harm to the environment is minimalised, and take part in activities to raise awareness of conservation issues.
- Tourists have to pay entrance fees - this brings in more money for rainforest conservation. Profits are invested in education projects to promote conservation in the local community.