Geography Notes from year 10
Geography Notes
Coasts
- A coast is a place where the sea meets the land.
There are different types of waves:
- Destructive – backwash bigger than swash, frequent, tall, short wavelength.
- Constructive – swash is bigger than backwash, less frequent, low height, long wavelength.
Constructive waves are able to build the beach because the swash is stronger than the backwash. Destructive waves destroy the beach. The backwash is greater than the swash, so material is taken back out to sea with every wave.
Coastal Processes
- Erosion – when water wears away at rock.
- Transportation – when material is moved from one place to another.
- Deposition – when material is dropped in a place.
- Swash – movement of a wave up the beach.
- Backwash – movement of a wave back down the beach under gravity.
Factors affecting type of wave
- Wind speed
- Wind duration – the longer wind blows, the more energy a wave has.
- Fetch – distance of sea over which the wind blows. Longer = destructive waves.
- Attrition – particles carried by the waves, crash against each other and are broken up into smaller particles.
- Abrasion – particles carried by the waves crash against the cliffs, eroding the cliffs.
- Solution – the seawater slowly dissolves the cliffs. The material produced is carried away by the process of solution.
- Hydraulic action – waves have great energy which is released as they break against the cliffs. Waves trap air in cracks in the rock. This air is compressed by the waves, eventually causing them to crack.
More simply
- Attrition – rocks/pebbles hitting each other.
- Abrasion – sandpaper effect of rock grinding cliffs.
- Solution – Rocks dissolve.
- Hydraulic action – sheer force of water.
Headlands and bays
- The coast is made up of alternate hard and soft rock.
- Waves attack the coast.
- Waves erode the soft rock fast than hard rock.
- The eroded rock leads to BAYS which are inlets in the coast.
- The hard rock leads to headlands which jut out into the sea.
Formation of a stack
- Waves attack a line of weakness in the headland called a fault. Over time, the fault is eroded and becomes a cave. Over time, the cave is eroded nd becomes an arch. Over time, the roof at the arch collapses and an isolated column of rock called a stack is left.
Long shore drift
- Waves attack the coast at an angles due to the prevailing winds.
- The grain of sand is transported up the beach t the angle of the waves.
- The grain of sand comes back down the beach in a straight line due to gravity.
Wave cut notch
- Above the wave-cut notch an overhang develops. As the notch becomes larger, the overhang will become unstable. This is because of its weight and lack of support. In time the overhang will fall due to the pull of gravity.
- The sea continues to attack the cliff in this way and the cliff retreats.
- As the width of platform increases the power of the sea decreases because it has further to travel to reach the cliff and the water is shallower causing more friction.
- The remains of the cliff, now below sea at high tide, form a rocky wave cut platform. The platform will also contain the boulders, which have fallen from the cliff.
- The cliff is eroded at the bottom by abrasion. This is the pebbles carried by the sea which are thrown against the cliff by the breaking waves, knocking off parts of the cliff. In time, a wave-cut notch is formed.
Depositional landforms
- Tombolo forms when a beach or sand spit joins up with an offshore island.
- Barrier islands are sand islands that run parallel to the coastline forming a tidal lagoon between them and the shore.
- Sand spit is a long, narrow stretch of sand with one end attached to the mainland.
- Sand bar develops when a spit stretches across a bay linking two headlands.
- Saltmarsh is a sheltered area flooded at high tide, where silt collects behind a sand spit of sand.
- Sand dunes are formed by winds blowing dry and from the beach inland and depositing it there is form mounds of sand on which marram grass and other plants grow.
Depositional landforms
Formation of a spit
- Waves attack and erode the coast line.
- The coastline is eroded and material transported in the direction of waves.
- The eroded materials is deposited where the coast changes direction (or at the river mouth) due to a loss of energy/velocity.
Coral Reefs
- Coral reefs provide employment for millions of people and supply seafood, building materials, medicines and the income from tourists.
Natural threats are
- Earthquakes
- Storms
- Temperature
The human threats are
- Tourists stepping on coral
- Blast fishing
- Cyanide bomb
- Coral being sold
- Anchors being dropped onto coral
What is GBRMPA
The Great Barrier Reef Marine Park Authority (GBRMPA) is an organisation, which aims to protect the reef. To achieve this, they are developing laws to stop oil pollution, over-fishing and tourist damage. They have made different zones for different activates and the managers are told to keep the natural beauty of the reef.
Plate tectonics
The Earth’s structure
- The core is white-hot solid iron
- Mantle is molten rock magma
- Crust is thin rock (20-60km)
An apple has a core just like the earth and the juicy part of the apple is like the magma of the earth. An apple has skin, which can represent the earths crust.
- The study of plates is called plate tectonics.
- Magma is molten rock inside the earth’s surface.
- The crust is broken into many smaller pieces called plates.
Distribution of volcanoes and earthquakes
- 99% of volcanoes and earthquakes occur on plate boundaries.
- There is a band of activity down the west coast of North and South America.
- There is activity across south Europe.
- There are volcanoes and Earthquakes down the middle of the Atlantic Ocean.
- There is a ring of activity around the Pacific Ocean. This is known as the Ring of Fire.
- There is no activity in Britain and Australia.
There is proof that the Red Sea is parting. There is an 8-meter crack as the African plate and the Arabian plate are being pushed apart. Magma is filling the crack from the mantle, which the cools to form no crust. The widening is usually about 30 mm per year, but the sea floor is more rapid.
The plates are made up of 2 types of crust.
- Oceanic crust forms under the oceans. It is constantly being formed and destroyed.
- Continental crust makes up the worlds major continents. It is more stable, older, and lighter than oceanic crust.
Landforms crated at plate boundaries.
| Boundaries | Fold mountains | Volcanoes | Earthquakes | Trench |
| Destructive | Yes | Yes | Yes | Yes |
| Collision | Yes | No | Yes | No |
| Constructive | No | Yes | Yes | No |
| Conservative | No | No | Yes | No |
- Convergent is a plate that is destructive so it is pushing together.
- Divergent is a plate that is constructive so it is pulling apart.
- A subducting plate is a plate that is going under another plate.
Volcanoes
Why volcanoes occur at…
Divergent plate boundaries (aka constructive – where plates pull apart).
- Plate move apart.
- Gap/line of weakness create in crust.
- Magma rises.
- Lava solidifies (hardens) to create volcano after eruption.
Convergent PB (aka destructible –plates move together and one (oceanic) sub ducts.
- Oceanic crust subducts under continental because it is heavier.
- This leads to friction.
- Oceanic crust is destroyed in mantle and turns into magma.
- This creates pressure.
- Magma rises through line of weakness.
Why do people continue to live near volcanoes?
- Fertile soil-ash provides nutrients. Good for farming.
- Geothermal power-jobs. (Steam roves electricity).
- Tourist attraction-tour guides, souvenirs .
- Close to family.
- No choice-poor people can’t move away.
- Beautiful scenery.
- Volcanologists – researchers.
What erupts from a volcano?
- Molten rock (lava)
- Ash
- Steam
- Gas
- Volcanic bombs (hard lava rocks)
Earthquakes
Focus
This is the point in the earths crust were the rocks break and the earthquake starts.
Seismic Waves
Seismic waves are the tremors caused by the breaking of the rock. Under the surface the seismic waves travel vertically. When they reach the earths surface they travel laterally (side ways).
Epicentre
The centre of the earthquake on the earth’s surface.
Weathering
Erosion is wearing away and removal of rock by moving forces (water, ice, wind). Weathering is the break down of rock (in situation it is not removed).
There are three main types of weathering.
- Mechanical (physical). This is the disintegration of the rock.
- Freeze – thaw e.g. Lake district, UK in winter.
- This is when acid in the rain reacts with minerals in the rock. This is known as decomposition.
- Rainwater + carbon dioxide = carbonic acid. Carbonic acid attacks rocks through crack. Limestone is good example at rock vulnerable to this.
- O2 in air combines with iron in rocks. This expands the rock and breaks down as rust. Rock looks red-brown.
- This is when animals or plants bury into rocks and break them down.
Biological weather
This is due to the action of plants and animals. Seeds may fall into cracks in the rocks where shelter and moisture help them grow into small plants or trees. As the roots develop they gradually force the cracks to widen and rock to fall apart. Eventually whole rocks can be brocken into small pieces. Burrowing animal such as rabbits, mole and even earthworms can also help break down the rock.
Freeze-thaw weathering
This can also be called frost shattering. Water may get into a crack in a rock and freeze as the water turns to ice it expands and causes the crack to open a little. When it thaws the ice melts and changes back to water. Repeating freezing and thawing weakens the rock and splits it into jagging pieces. The type of weathering common in mountainous areas where temperatures are often around freezing point.
Exfoliation weather.
This happens when a rock is repeatedly heated and cooled. As it is heated, the outer layer of the rock expands slightly and as it cools the rock contracts. Continual expansion and contraction causes small pieces of the rock surface to peel of like the skin of an onion. This type of weathering is common in desert areas where it is very hot during the day but cool at night.
Types of weather are:
- Snow
- Sunny
- Rain
- Frost
- Sleet
- Hail
- Mist
Climate is the average weather conditions over a period of 30 year minimum.
Weather instruments
- Rain gauge – daily rainfall – mm
- Maximum – minimum thermometer – temperature – Celsius
- Wet and dry bulb thermoment (hygrometer) – humidity – %
- Barometer – air pressure – millibars mb
- Cup anemometer – wind speed – km/hr
- Wind vane – direction wind is blowing – N,E,S,W
- Temperature is measured in Celsius or farenhight.
- Wind strength is measured in kilometres an hour.
- Wind direction is measured in north, south, east and west
- Cloud cover is measured in eighths.
Different clouds
- Huge cloud that causes big storms.
- Dome like cloud.
- Flat straight cloud.
- Feather like wispy clouds.
Tropical rainforests.
A tropical rainforest is an ecosystem. An ecosystem is an environment in which the living (animals and plants) and the non living (leafs and soil) things in an area interact with each other.
The Stevenson screen
A traditional weather station has a Stevenson screen. It is built so that the shade temperature of the air can be measured. It consists of a square wooden box on a stand. The box has louvered sides to allow the entry of air. The rood is made of double boarding to prevent the sun’s heat from reaching the inside of the screen. Insulation is further improving by painting the outside white to reflect the sun’s rays. It is places on a stand 110 cm above ground level to avoid any effects of concrete or grass at the surface. It is sited in open space, clear of trees and buildings to avoid any obstacles affecting the readings. In this way instruments inside the screen avoid external influences.
What is the relationship between climate and vegetation in a rainforest?
Climate – hot and wet (humid).
These are perfect growing conditions. Large amounts of vegetation. Daily sun leads to evergreen trees. Leaves have drip-tips to releases water. Emergent grow tall to reach sun for photosynthesis.
When leaves fall and animals due, they end up on the forest floor. The humid conditions lead to them decomposing quickly. This creates humus which provides nutrients for the soil which leads to more growth.
Deserts
A desert is an area that receives less than 250mm of precipitation per year. Arid deserts con be hot or cold. We are looking at hot deserts. They are mostly found in the west of continents as the prevailing winds come from the east and so winds that reach the desert areas have no moisture/rain.
Why does it not rain in a tropical desert?
- Prevailing winds blows in from the East (known as westerly’s).
- Clouds travelling over oceans have lots of moisture.
- When clouds meet land, they are forces to rise … so they rise, cool condenses … and it rains.
- By the time these clouds reach the west side of the continent, precipitated all their moisture … and so its dry = DESERT!
The saguaro cactus in the state flower Arizona, USA. The blossoms open during desert nights and close in the day. It has a tall; thick stem with smooth waxy skin and 20 mm spines. The stem can expand to store water.
Land degradation caused by human activity.
- People and animals move.
- People and animals stay.
- Overgrazing, over cultivation, deforestation.
- More bare ground exposed; more wind erosion.
- The Sahel extends.
Tropopause is the boundary between the atmosphere and space rising air can’t penetrate it.
- The sun is overhead at the equator. Air is heated and so it rises.
- Upon reaching the tropopause, this air moves N and S towards the tropics.
- As the air cools, it sinks again at the tropics.
- Sinking air leads to high pressure. In high pressure conditions, rain cannot occur = DESERT!
Rivers drainage basin
An area of land draining by a river and it’s tributaries.
- Watershed is the edge of the drainage basin (high mountainous land).
- Source is the start of river.
- Mouth is the end of a river (where it meets the sea).
- Tributary is a small stream that joins the main river.
- Confluence is where 2 rivers.
River channel – the place where the river flows.
Processes of Erosion, erosion is the process in which a river wears away material from its river banks or river bed. There are 4 types
- Abrasion: sand and stones in the river scrape the bed and banks, wearing them away. Sandpaper effect of rocks on the bed and banks.
- Attrition: Rocks and stones knock together and wear each other away. Rock hit each other.
- Hydraulic action: In a fast-flowing river, water is forced into cracks in the bank. Over time it breaks up the bank. Sheer force of water.
- Solution: Water also dissolved soluble minerals from the bed and banks. This helps to break them up. Rocks dissolved.
The upper cause, the main process is vertical erotsion (as the river ends downwards through the mountains).
In the lower course, the mian process is lateral erosion (sideways) (as the river meanders in the lowland).
The rocks, pebbles and stone that a river transports and called its load.
Rapids – a small step in the river. “White water”.
Rapids are sections of a river where the gradient of the river bed is relatively steep resulting in an increase in the river’s turbulence and velocity. They form where the gradient of the rivers in steep and the bed is composed mainly of hard rocks.
On a different note
A river flows over hard and soft rock. The soft rock is easier to erode so the hard rock creates and overhang.
Hydraulic action and abrasion erode the soft rock to create a plunge pool.
There is nothing underneath the hard rock to support it so it eventually collapses into the plunge poo.
The waterfall retreats (moves back ) up the river, eventually creating a steep-sided gorge.
Potholes
Potholes are cylindrical holes drilled into the bed of a river that vary in depth and diameter from a few centimetres to several metres. They’re found in upper course of a river where it has enough potential energy to erode vertically and its flow is turbulent. In the upper course of a river, its load is large and mainly transported by traction along the river bed. When flowing water encounters along the river bed. When flowing water encounters along the river bed. When flowing water encounters bedload, it is forces over it and downcuts behind the bedload in swirling eddie currents. These currents erode the river’s bed and create small depressions in it.
Explain how oxbow lake is formed, model answer
The velocity of the water moves fastes on the oustside of the bend, which causes it to erode laterally.
This causes the necks of the meander to become closer together.
The river breaks through creating a straight channel and the water takes the quickest route.
This means that the speed of the water in the bend slows down and sediment is deposited at the entrance and exit of the bend.
This cuts off the bend and an oxbow lake is formed
Floodplain – area of flat, fertile land enter side of river channel. When a river floods, the water spreads out over a larger surface area. This increases friction which leads to a reduction in velocity/energy and so deposition occurs. Larger (coarse) materials is dropped first and then smaller material. Over many floods, flat land builds up either side of the channel leading to a fertile floodplain and silt and alluvium are deposited.
River Delta
River deltas occur at the mouth of a river where the river meets the sea. At this point the river looses its velocity and energy and therefore deposition occurs. Deltas build up in the form of fertile land which in time is in habited by people due to fertile soils. E.G. Ganges Delta, Nile Delta.
Causes of river floods
Physical (natural)
- Heavy rainfall
- Saturated soil
- Small drainage basin
- Steep slopes
- Snow melt
Human
- Urbanisation
- Deforestation
All lead to water running across the surface and getting to the river channel quickly.
Opportunities of living on a floodplain, delta or near a river.
- Agriculture (farming, fertile soil)
- Good water supply – drinking, cleaning, washing
- Scenic
- Tourism
- Travel
- Ships/cargo
- Leisure – sailing
Population
DR- death rate – number of deaths per 100= per year
BR – birth rate – number of births per 1000 per year
Natural Pop. Change in BR – DR
Overall Pop. Change in BR – DR + migration.
Infant mortality – number of children per 1000 live births who die before their first birthday.
Overpopulation – Too many people for the resources available
– e.g. India
Under population – Not enough people to use up the resources so the resources are wasted – Australia
Optimum population – the correct amount of people for the recourses available – Germany
A large pop does not necessarily means it’s over pop. A small pop does not necessarily mean its under pop.
Problems caused by overpopulation
- Lack of food.
- Lack of housing.
- Pressure of schools.
- Loss of wildlife.
Population Structure and Control
Census
A census is a population count. In the UK a census is done every 10 years with the last one being in 2011. A census tells the government important information on:
- Total population.
Problems with a Census
In many LEDCs, census’s are not carried out:
- They are too expensive.
- Government has other priorities.
- Areas of the country are inaccessible.
- Some people don’t have permanent homes.
- Many people are illiterate (can’t read).
Fertility Rate – The average number of children to which each woman gives birth.
Problems of an ageing population (Italy)
- Need to provide more healthcare, e.g. retirement homes, hospital beds, undertakers.
- Taxes need to be increased to provide for increased to provide for increased old people on pensions.
- Money spent on services for the elderly people, e.g. bingo halls instead of nightclubs.
Problems of a youthful population (Gambia)
- High dependency ratio – not enough working age people to support the young.
- Financial problems – not enough money to feed all of the children (malnutrition).
- Homes are often overcrowded.
- Sanitation is very poor.
Geography Case studies 