GCSE Geography A Unit 1 - Restless Earth notes
Using notes for Restless Earth, according to AQA syllabus
Terms in this set (92)
Restless Earth Topic
Revision cards on restless earth
What are the layers of the Earth?
The earth is made up from an inner core, outer core, mantle and crust.
How is the crust divided?
It is divided by lots of slabs called tectonic plates, (floating on the mantle)
What are the two types of crust and their properties?
Continental crust and Oceanic crust. Continental crust is thicker and less dense than Oceanic which is thinner and denser.
Why do the plates move?
The plates are moving because the rock in the mantle underneath them is moving.
What is the meeting of two plates called?
The places where plates meet are called boundaries, or plate margins.
What occurs at Destructive plate margins?
• Oceanic and continental plates push together.
• Denser oceanic crust forced down into Earth's mantle (subduction) forming an ocean trench.
• Continental Crust is compressed to form Fold Mountains with composite volcanoes.
• Major Earthquakes occur when the plates move.
What are Conservative margins?
• Plates are moving sideways past each other or are moving in the same direction but at different speeds.
• Plates remain locked together until the rock breaks along the fault line.
• Major earthquakes occur as the stored energy is released.
• There are no volcanoes.
What occurs at Constructive plate margins?
• Oceanic or continental plates pull apart.
• Lava erupts forming shield volcanoes.
• Undersea volcanoes form mid-ocean ridges.
• Major earthquakes occur when the plates move.
What is Subduction?
The sinking of oceanic crust at a destructive margin.
What is a Collision?
The meeting of two plates of continental crust. They are both the same type so they meet 'Head On' and buckle.
What is a Ocean Trench?
Deep sections of the ocean, where an oceanic plate is sinking below a continental plate.
How and where are Ocean Trenches formed?
They are formed offshore at destructive plate margins (subduction zones)
when the denser oceanic plate sinks below the less dense continental plate.
How deep can Ocean Trenches be?
They are the deepest parts of the ocean can be over 10,000m deep (at the Mariana Trench)
What is a Fold Mountain?
Large mountain ranges where rock layers have been crumpled as they have been forced together.
How are Fold Mountains formed?
• Formed on destructive plate margins.
• Rivers carry sedimentary rocks such as sandstone and limestone.
• They are deposited into depressions.
• After a few million years the sediments are compressed into sedimentary rocks then forced upwards into a series of folds by the movement of tectonic plates.
Give examples of Human activity on Fold Mountains:
• Farming: higher mountain slopes not good for farming, but good grazing land. Land can be terraced to accommodate crops.
• Mining: Fold Mountains major source of metal ores, however the steep slopes have to be carved into zigzag roads for easy access.
• Hydro-electric power (HEP): Steep slopes and lakes ideal for generating HEP.
• Forestry: Can grow conifers, used for fuel, building materials and paper and furniture.
• Tourism: Scenery, winter sports, summer walks. Tunnels have been built for fast communications.
Fold Mountain CASE STUDY
Questions on Alps case study
Where are the Alps?
Central Europe, form a border between Italy and neighbouring countries of France, Switzerland and Germany.
When were they formed? And between what plates?
About 30 million years ago by collision between Africa and European plates.
What is the tallest peak?
Mount Blanc (4810m) on Italian French border.
What is a Volcano?
An opening or vent in the earth surface through which molten material erupts and solidifies as lava.
Where are Volcanoes found?
They are found at destructive AND constructive plate margins.
What is a Composite Volcano?
A Volcano with alternate layers of lava and ash.
Give some examples of Composite Volcanoes:
Mount Etna, Vesuvius, Mount St Helens.
What are the Characteristics of Composite Volcanoes?
• Steep-sided symmetrical cone shape.
• High with narrow base.
• Alternate layers of acid lava and ash.
• Lava may cool inside the vent - the next eruption is very explosive to remove the plug.
• Subsidiary cones and vents form.
• Eruptions don't happen often, but when they do they are explosive, e.g. Mt St Helens.
• Found on destructive plate margins.
How do Composite Volcanoes form?
1. Lava builds up in a magma chamber underneath the volcano. This can be added to as more oceanic crust melts at the plate margin.
2. The lava is very thick and clogs up the main vent of the volcano, causing a 'plug' effect.
3. The pressure build-up causes an explosion which blows out ash, gas and lava.
4. The lava runs down the sides, then when it cools, these layers of the lava become the sides.
Give some examples of Shield Volcanoes:
Mauna Loa and Kilauea, which are both on the Hawaiian Islands.
What are the Characteristics of Shield Volcanoes?
• Gentle slopes and wide base
• Frequent eruptions of basic lava
• Lava flows more easily, travels longer distances before cooling.
• Usually non-violent.
• Found on constructive plate margins.
How do Shield Volcanoes form?
1. Two plates move apart from each other and magma rises up.
2. This magma continually forms new layers of rock until it reaches the surface, forming a cone.
What are the Primary and Secondary effects of Volcanic Eruptions?
• Primary effects - The immediate impact of the volcanic eruption, e.g. Loss of life, loss of homes, animals and crops.
• Secondary Effects: The after-effects of the eruption, such as the loss of trade including tourism, the need to rebuild, the stress for people.
What are the positive impacts of Volcanoes?
• Fertile soil when the lava weathers.
• Tourist attraction, e.g. Trips to the rim of the crater, hotel accommodation, souvenir shops.
• Minerals, e.g. Sulphur, borax, pumice.
• Lava flows build new islands e.g. Iceland, Hawaii.
• Heat used to generate electricity.
What are the negative impacts of Volcanoes?
• Explosions and eruptions leading to: Dangerous gases; loss of life; loss of homes; animals and crops; disease and fires; avalanches, mudflows and floods; loss of wildlife, trees and plants.
Volcano CASE STUDY
Notes on case study: Soufriere Hills in Montserrat
When did Soufriere Hills erupt?
June 25th 1997
How many were killed?
What caused the eruption? - Soufriere
• Montserrat is above a destructive plate margin, where the Atlantic Plate is being forced under the Caribbean plate.
• Magma rose, forming an underground pool of magma.
• The rock above the pool collapsed, opening a vent and causing the eruption.
What were the primary impacts of the eruption? - Soufriere
1. Large areas were covered in volcanic material- the capital city, Plymouth was buried under 12m of mud and ash.
2. Over 20 villages and two thirds of homes on the island were destroyed by pyroclastic flows (fast moving clouds of super-heated gas and ash).
3. Schools, hospitals, the airport and the port were destroyed.
4. Vegetation and farmland were destroyed.
5. 19 People died and 17 were injured.
What were the secondary impacts of the eruption?
1. Fires destroyed many buildings including local government offices, the police headquarters the town's central petrol station.
2. Tourists stayed away and businesses were destroyed disrupting the economy.
3. Population decline - 8000 of island's inhabitants have left since the eruptions began in 1995.
4. Volcanic ash from the eruption has improved soil fertility.
5. Tourism on the island is now increasing as people come to see the volcano.
What were the immediate responses to the eruption? - Soufriere
1. People were evacuated from the south to safe areas in the north.
2. Shelters were built to house evacuees.
3. Temporary infrastructure was also built, e.g. roads and electricity supplies.
4. The UK provided £17 million of emergency aid (Monserrat's an overseas territory of the UK).
5. Local emergency services provided support units to search for and rescue survivors.
What were the long-term responses to the eruption?
1. A risk map was created and an exclusion zone is in place. The south of the island is off limits while the volcano is still active.
2. The UK has provided £41 million to develop the north of the island - new dock, an airport and houses have been built in the north.
3. The Montserrat Volcano Observatory has been set up to try and predict further eruptions.
What is a Super Volcano and give an example of on:
A mega colossal volcano that erupts at least 1,000km of material. E.g. Yellowstone
What is a Caldera?
The depression of the supervolcano marking the collapsed magma chamber.
What is a hotspot?
A section of the earth's crust where plumes of magma rise, weakening crust. These are away from plate boundaries.
What are the characteristics of a Super Volcano?
• Cover a much bigger area than normal volcanoes.
• They found in fewer locations than normal volcanoes - destructive plate margins and hotspots.
• They are flat (unlike normal volcanoes which are mountains).
• They have large depression called a caldera with a rim of higher land around it.
How do Super Volcanoes form?
1. Rising magma cannot escape, and a large bulge appears on the surface.
2. Cracks appear in the surface and gas erupts from the magma chamber.
3. The magma chamber collapses forming a depression called a caldera.
What are the general consequences of a Super Volcano eruption?
• An eruption will throw out thousands of cubic kilometres of rock, ash and lava (Normal volcanoes produce a couple of cubic kilometres).
• A thick cloud of super-heated gas and ash will flow at high speed, killing, burning and burying everything it touches within up to 100 miles.
• Ash will shoot kilometres into the air and block out almost all daylight over whole continents. This can trigger mini ice ages as less energy from the sun gets to Earth.
• The ash will settle over hundreds of square kilometres, burying fields and buildings (ash from normal volcanoes usually cover a couple of square kilometres.)
CASE STUDY: What are the likely effects of a eruption from Yellowstone?
• Destroy 10,000 km2 of land.
• Kill 87,000 people.
• 1 in 3 affected would die.
• Ash would effect: Transport, Electricity, Water and Farming.
• Ash over UK five days later.
• Global climates would change, crops would fail and people would die.
Why do earthquakes occur at Destructive Margins, Constructive Margins and Conservative margins?
• Destructive Margins: Tension builds up when one plate gets stuck as it's moving down past the other into the mantle.
• Constructive Margins: Tension builds along cracks within the plates as they move away from each other.
• Conservative Margins: Tension builds up when plates that are grinding past each other gets stuck.
What are the Characteristics of a Earthquake?
• The plates eventually jerk past each other sending out shockwaves (vibrations) = earthquakes.
• The wave spread out from the focus (the point in the Earth where the earthquake starts).
• The nearer the focus the waves are more destructive and stronger they are.
• The epicentre is the point on the Earth's surface straight above the focus.
Give three ways that Earthquakes are measured:
• The Richter scale: The strength of earthquakes is generally given according to the Richter scale. There is no upper limit to this scale. The logarithmic nature of the scale means that there is a 10-fold increase every time the scale increases by 1. So a scale 2 earthquake on the Richter scale is 10 times more powerful than a scale 1 etc. A line graph produced is called a seismogram shows the extent of shaking.
• The Mercalli Scale: Measures how much damage is caused by the earthquake based on observations. It is measured on a scale between 1 and 12.
Give some examples of the Mercalli scale:
1. Barely Felt
3. Slightly felt indoors as though a large truck were passing.
6. Felt by everyone; some are frightened and run outside; some chimneys break, some furniture moves, slight damage.
9. Underground pipes break; foundations of building are damaged and buildings shift off foundations; considerable damage to well-built structures.
12. Total destruction; objects thrown into air; the land appears to be liquid and is visibly rolling like waves.
CASE STUDY - Kobe Earthquake
Facts on Kobe Eathquake
Where is Kobe located?
South of Japan on the main island of Honshu
When did it happen? - Kobe
Tuesday, Janurary 17th 1995, at 5.46 am
How many CM's is the denser oceanic Philippines plate is being subducted beneath the lighter continental Eurasian plate?
What Magnitude was the earthquake?
7.2 on the Richter scale.
What was the population of Kobe?
Population of about 10 million people
How long did the Earthquake last?
How many people died?
How many became homeless?
How much did the damage cost and what to?
£100 billion was caused to roads, houses, factories and infrastructure.
What caused the Earthquake? - Kobe
1. Philippines Plate moves towards Eurasian plate.
2. Philippines plate is forced down as it is oceanic crust.
3. Plates jam together and pressure builds up.
4. Pressure is suddenly released and plate jerks forward.
5. Earthquake shockwaves travel outwards.
This occurred along the Nojima fault line that runs beneath Kobe.
What were the immediate responses to the earthquake?
• Emergency services responded to rescue people trapped or injured and to put out the fires.
• Emergency shelters were set up in public buildings and food, water and blankets were given to the homeless.
• Emergency gas crews worked to stop gas leaking and starting new fires.
• Motorolla maintained phone connections free of charge.
What were the long-term responses to the earthquake? - Kobe
• 80% of the port was working 1 year after the earthquake
• By January 1999, 134,000 housing units had been constructed.
• New laws were passed to make buildings and transport more earthquake proof.
• Schools and factories have regular earthquake drills.
• More instruments were installed in the area to monitor earthquake movements.
• Buildings built further apart.
• Rubber blocks under bridges - absorbs shockwaves.
What were the short term effects of the earthquake? - Sichuan
• Over 100,000 houses collapsed.
• Over 6,000 people died
• Over 40,000 injured.
• 300,000 homeless.
• City infrastructure - a lot destroyed.
• Roads collapsed - Top deck of Hanshin highway.
• Gas mains destroyed.
• Water leaks.
• millions without electricity and water.
• 10% schools, 12% and 14% services destroyed.
What were the long-term effects of the earthquake?
• Fire raged for a long time, burning wooden structures - Destroyed 7,500.
• Companies such as Panasonic had to close temporarily.
• £2000 billion - what the earthquake cost!
• 1300 after shocks
• People slept in tents in parks. - flu epidemic.
• Health hazards in the makeshift shelters.
CASE STUDY - Earthquake in a poorer part of the world: Sichuan, China
Notes on Sichuan Earthquake
What is the economic state of Sichuan?
When did the earthquake happen?
What did it measure on the Richter scale? - Sichaun
What plates were involved?
At the junction of the Indian (Oceanic) and Eurasian (continental) plates - A destructive margin.
What were the primary effects of the earthquake?
• 69,000 killed.
• 400,000 injured.
• 5 million homeless.
• 5 million building collapsed (No building regulations) 80% of rural areas like Beichuan.
• Schools collapsed, killing thousands.
• Roads blocked by landslides.
• No telephones worked.
What were the secondary effects of the earthquake?
• $75 million of damage.
• Landslides blocked rivers, leading to floods.
What were the immediate responses to the Earthquake?
• Access was difficult - helicopters needed.
• Troops parachuted in to help free trapped survivors.
• Immediate need for clean water, food, tents and medicines.
• China asked for help from Russia and Japan.
• International aid agencies e.g. Red Cross raised money to help.
• Land flattened to erect tents.
What were the long-term effects of the Earthquake?
• Temporary homes built.
• Debts of people who did not have insurance cancelled by banks.
• Likely to take 3 years to complete re-building.
What factors affect the effects of the Earthquake?
• Magnitude - Strength, Richter scale.
• Rural or Urban - Urban more populated.
• Size of population - More people, more dead.
• Quality of buildings - low quality collapsed.
• Time of day - Busy in day.
• MEDC or LEDC - LEDC less developed building, less access.
• Communications links - Easy or hard to get to survivors.
• Availability of emergency services - more services, more help.
• Spread of disease - more people together, more disease.
Why are the effects of Earthquakes more severe in poorer countries?
1. More low quality housing in poorer countries - less stable, so destroyed more easily.
2. Infrastructure often worse. Poor quality roads means it's harder for emergency services to reach injured people which leads to more deaths.
3. They don't have as much money to protect against earthquakes e.g. by making buildings more resistant to them. They may not have enough money or resources (food and emergency vehicles to react straight away) so more people are affected by secondary impacts.
4. Health care may not be as good. Many hospitals do not have enough supplies to deal with lots of casualties so more people die from injuries which were treatable.
What is a Tsunami?
A special type of wave where the entire depth of the sea or ocean is set in motion by an event, often an earthquake, which displaces the water above it and creates a huge wave.
How are Tsunamis triggered?
Tsunamis are usually triggered by earthquakes. The crust shifting is the primary effect; a knock-on (secondary) effect of this is the displacement of water above the moving crust. This is the start of a tsunami.
How do Tsunamis form?
1. If one tectonic plate is dragged beneath another, stress on the boundary causes the edges of the plates to flex and deform.
2. The flexing of the plate displaces the entire column of water vertically.
3. Quickly the water column splits into two with one wave travelling out to sea and the other towards the coast.
4. The tsunami comes ashore and can surge far inland. Often secondary waves are more powerful than the initial one.
CASE STUDY: The Indian Ocean Tsunami
Notes on the Indian Ocean Tsunami
When did it happen?
26 December 2004
What was the epicentre of the Earthquake and its Richter scale?
Indian Ocean floor - west of Sumatra, Indonesia. Richter scale 9.2
Why did the plates cause a tsunami?
Movement along the destructive plate margin between the Indo-Australian and Eurasian plates caused a very powerful series of earthquakes. A 1000km long break in the crust raised the sea bed by 12m.
What were the effects of the Tsunami?
• Number of deaths: 220,000.
• Number of injured: 650,000. Number made homeless: 2 million.
• School and hospitals wiped out.
• 1,500 settlements wiped out in Banda Aceh:
What happened in Indonesia?
• Province of Aceh on northern tip of Sumatra Island badly hit, including provincial capital Banda Aceh.
• Dozens of buildings destroyed in the initial earthquake before flood waters washed over the region.
What happened in Sri Lanka?
• Wide stretch of eastern and southern coastline devastated by massive waves.
• Districts of Mutur and Trincomalee inundated by waves as high as 6m.
• Port of the capital, Colombo, hit by flash floods.
What happened in India?
• Large areas of eastern coast swamped by tidal waves.
• Deaths reported in the Andaman and Nicobar Islands and Kerala state.
What happened in Thailand?
• Western coast of southern Thailand badly affected, including Phuket and Phi Phi Island.
What were the immediate responses to the tsunami?
• Fresh water, water purification tablets, food, sheeting and tents all poured in as aid.
• UK government promised £75 million and public donations of £100 million followed.
• Injured people left untreated for days. Bodies littered in streets and the buried in mass graves.
• Rescue services and emergency teams swamped by scale of the disaster.
What were the long-term responses to the tsunami?
• £400 million had been donated by the British public but only £100 million had been spent by the disasters emergency committee (DEC)
• Rebuilding was progressing and DEC has spent £40 million on projects in Sri Lanka and Indonesia.
• Plans to spend a further £190 million in the second year, building 20,000 houses for 100,000 homeless people.
• Indian Ocean Tsunami warning system set up in June 2006. Ensuring people know how to respond and that local authorities have plans in place are essential for its success.
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