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Geography Restless Earth GCSE Revision AQA Unit 1 Section A
Specification PART 1 The Earth’s crust is unstable, particularly at plate margins. Distribution of plates; Contrasts between oceanic and continental plates, Destructive, constructive and conservative plate margins Unique Landforms occur at plate margins. Location and formation of Fold Mountains, Ocean Trenches and Composite and Shield Volcanoes People use these landforms as a resource and adapt to the conditions within them. A case study of one range of fold mountains, including the ways in which they are used (Farming, Hydro Electric Power, Mining, Tourism and how people adapt to limited communications, poor soils and steep relief) Volcanoes are hazards resulting from tectonic activity. Their primary and secondary effects are positive as well as negative. Reponses change in the aftermath of the eruption. Characteristics of different volcanoes; A case study of a volcanic eruption – its cause, primary and secondary effects, positive and negative impacts, immediate and long term responses; monitoring and predicting volcanic eruptions
Specification PART 2 Supervolcanoes are on a much bigger scale than other volcanoes and an eruption would have global consequences. The characteristics of a supervolcano and the likely effects of an eruption Earthquakes occur at constructive, destructive and conservative plate margins. Location and cause of earthquakes; features of earthquakes – epicentre, focus, shockwaves and the measurement of earthquakes using the Richter and Mercalli scales The effects of earthquakes and responses to them differ due to contrasts in levels of wealth. A case study of an earthquake in a rich part of the world and one from a poorer area – their specific causes, primary and secondary effects, immediate and long term responses and the need to protect, predict and prepare; contrasts in effects and responses will be clear Tsunamis are a specific secondary effect and can have devastating effects in coastal areas. A case study of a tsunami – its cause, effects and responses
GCSE Case Studies You must include: Background Information (Location, date, time etc.) Cause (Refer to processes, and be specific using technical language and key terms) Effects: Primary and Secondary Impacts: Positive and Negative, Social, Economic, Environmental and Political (SEEP) Responses: Short Term, Long Term – Use SEEP Remember to be as specific as possible, using actual facts and figures and answering the question
Restless Earth - Revision
Structure of the Earth Crust Upper Mantle Lower Mantle Outer Core Inner Core The Upper Mantle and Crust together are called the Lithosphere. The Lower Mantle is also called the Asthenosphere.
Structure of the Earth
Historical Plate Tectonics
Divergent / Constructive Plate Boundaries This is where new crust is generated as plates pull away from each other (e.g. Mid-Atlantic Ridge between North American and Eurasian Plates)
This means that oceanic crust is destroyed. An example of this is along the West Coast of America. Convergent / Destructive Plate Boundaries This is an example of Subduction where an oceanic (dense) plate collides with a continental (less dense) plate.
Fold Mountains are formed when rivers deposit sediments on the ocean floor, and as the plates are pushed together, the sediments are forced upwards into fold mountains. Convergent / Destructive Plate Boundaries When two continental crusts meet, mountains are formed (e.g. the Himalayas) – this is NOT destructive.
Transform / Conservative Plate Boundaries Plates slide past each other and crust is not produced or destroyed (e.g. North American plate and Pacific plate)
Plate Boundary Zones Less defined boundaries where the effects of plate interaction are unclear Example: African Plate
Fold Mountains and Ocean Trenches - Locations These are mainly at convergent (destructive) plate boundaries.
Hot Spots Hot Spots are sections of the Earth’s crust where plumes of magma rise, weakening the crust. AWAY FROM PLATE BOUNDARIES
Types of Plates Oceanic PlatesContinental Plates Newer – most less than 200 million years old Older – Most over 1500 million years old DenserLess dense Can sinkCannot sink Can be renewed or destroyedCannot be renewed or destroyed
Case Study – The Andes Longest continental mountain range in the world (Area – 3.3 million sq. km) Aconcagua – Largest point in the Andes at 6,962m elevation
Case Study – The Andes The Andes cover the Entire Western coast of South America. From North to South, the countries covered are Venezuela down to Argentina (see map). The Andes are not a single line of peaks, they’re actually a succession of parallel and transverse ranges.
Case Study – The Andes There are three sections of the Andes, each separated by intermediate depressions. They are a set of fold mountains, formed by the Nazca and South American plates.
How do people use The Andes? Agriculture HEP (Hydro Electric Power) Mining Tourism
Agriculture in the Andes For over 6,000 years, crops have been irrigated with spring water. Terracing has been installed to combat the steep slopes. Previously, maize and potatoes were the most important crops.
Agriculture in the Andes Nowadays, tobacco, cotton and coffee are the main export crops. Another important crop is coca is used for herbal tea and also illegally used for the production of cocaine.
HEP in the Andes Hydro Electric Power is easy to collect in the Andes because of their steep slopes and narrow valleys, with its fast running water. 174 dams for HEP are found in the Andes, and the elevation is perfect for the production of HEP.
Mining in the Andes Mining is popular because there are large deposits of certain ores and salts, as well as some hydrocarbons. There are huge copper deposits. There are also large potassium nitrate (saltpeter), lithium and silver deposits.
Tourism in the Andes Activities in the Andes include Trekking, Mountaineering, Rafting Trips and much more. The most famous trail is the Inca Trail. Tourism is controversial – some claim that traditional life is lost by tourism.
Tourism in the Andes Sustainability issues with Tourism include interrupted wildlife patterns, human buildings, erosion, roads, litter and use of helicopters.
Key Terminology Commercial Farming – For a profit Subsistence Farming – For survival
Types of Volcano Composite VolcanoesShield Volcanoes Destructive plate marginsConstructive plate margins Eruptions infrequent, but violentEruptions frequent, but non-violent Narrow base and steep slopesWide base and gentle slopes Have secondary conesLow, rounded peak Contains thick layers of lava and ash Layers of runny lava with little ash Mostly lava, oozes out
Types of Volcano Composite Shield There is a greater build up in pressure in Composite volcanoes
Case Study – Montserrat Volcano Background Information Located in Caribbean Sea near the Equator in a tropical location. On the Caribbean next to Atlantic plates. Population of 12,000 before the eruptions occurred.
Case Study – Montserrat Volcano Background Information Dense tropical forest. 104 square kilometres. £2800 – GNP per Capita (LEDC). Overseas Territory of Britain. Once called the Emerald Island.
Case Study – Montserrat Volcano Background Information The volcano itself is located in the South of the Island and called Mount Soufriere. The eruptions lasted from Composite Volcano that was peaceful before the eruptions.
Case Study – Montserrat Volcano Causes Originally a surprise, before lasting for 2 years (first eruption for 350 years). Subduction zone at destructive plate margin – composite volcano. Caribbean and Atlantic Plates.
Case Study – Montserrat Volcano Causes 1997 saw the worst volcanic activity. The lava flow was 600 o C, going at 20 km/h. The pyroclastic flows (fire with ash and mud) reached up to 130 km/h.
Case Study – Montserrat Volcano Primary (Immediate) effects 19 people died. The capital – Plymouth – was evacuated. Residents had to choose between leaving or staying put.
Case Study – Montserrat Volcano Secondary (later) effects Exclusion zone created (Southern part of the island). People forced to move people left the island.
Case Study – Montserrat Volcano Secondary (later) effects
Case Study – Montserrat Volcano Wider Impacts: Positive Encouraged people to go abroad (such as the UK). New start – Capital moved to Little Bay in the North of the island. Land more fertile people left in total.
Case Study – Montserrat Volcano Wider Impacts: Negative Economy devastated – no tourists. Half of the island is now uninhabitable. The new airport can only handle 20 seater planes. Main towns, communications and services destroyed.
Case Study – Montserrat Volcano Responses: Immediate Aid from London. Temporary schools made. Capital evacuated. Emergency food handed out. Southern area became exclusion zone.
Case Study – Montserrat Volcano Responses: Long Term Rioting over lack of British support. £200m support from Britain. New transport links created. Some people returned and tourists started to return to the island, but the population became a lot more aged.
Magma rises from the mantle to create a boiling reservoir in the Earth’s crust. This chamber increases steadily in size. When the chamber reaches its maximum capacity, the colossal pressure that has built up causes a super eruption. The term “Supervolcano” implies an eruption of magnitude 8 on the VEI Index (Volcano Explosivity Index). This means that more than 1,000 cubic kilometres (240 cubic miles) of magma (partially molten rock) erupt. They are not on plate boundaries. Ash can reach up to 30 or 40ft, and there is a 100 mile radius danger zone – this is the reach of a pyroclastic flow.
Key Terminology Caldera – Crater of a supervolcano (34 by 45 miles at Yellowstone) Fissures – Cracks in the ground Geysers – Ground water heated up Geothermal – Heat under the ground that heats the ground water
Main Supervolcanoes Toba, Indonesia Taupo, New Zealand (North Island) Long Valley, California, USA Longridge, Oregon, USA Yellowstone National Park, Wyoming, USA
More on Supervolcanoes Supervolcanoes are normally above hot and subducted zones.
Yellowstone Supervolcano 3 known supereruptions at Yellowstone. All of these have been on a 600,000 to 700,000 year cycle, starting 2.1 million years ago.
Yellowstone Supervolcano The last eruption was 640,000 years ago. On a geological timescale, this suggests that Yellowstone is overdue for an eruption.
Impacts of a supervolcanic eruption Local Total Devastation Pyroclastic flows Lots of ash and lava All in the area killed
Impacts of a supervolcanic eruption National 100 mile radius hit by pyroclastic flows Ash would block out the sun for 6 years, devastating food supplies Air travel effected Animal killed by the ash – no protection
Impacts of a supervolcanic eruption Global Ash would block out the sun for 6 years, devastating food supplies Air travel effected Entire change in global climate
Impacts of a supervolcanic eruption Continued – All areas A magma chamber of 80km by 80km by 40km could result in 2 – 3 cubic kilometres of ash with people trapped from a 300km radius. Inhaling of ash makes you drown in “liquid” concrete.
Impacts of a supervolcanic eruption Continued – All areas 100 tonnes of pumice, rock etc. Wall Street crash. People fighting to leave the country Need for back up generators. Traffic chaos, VEI 8, Everything closed, planes destroyed and multiple vents.
Pyroclastic Flows Can reach 800 km/h at 500 degrees Celsius.
Earthquakes Earthquakes can be defined as a shaking movement of the Earth’s crust. They can occur at any plate margin. In theory, earthquakes can occur at any place along the Earth’s crust, but 90% are found at plate boundaries.
Earthquakes Plates move because of a build up in pressure. The point where the energy is released is called the “focus”. The “epicentre” can be found directly above the focus.
Earthquakes Shockwaves (tremors) are strongest at the epicentre. There are primary and secondary waves.
Earthquake Scales Richter Scale – A scale that uses a seismograph to calculate the strength of earthquakes – its logarithmic nature means that each level is 10x more damaging than the one before – it’s scientific, accurate, easy to understand but not that accessible.
Earthquake Scales Mercalli Scale – A scale (from I to XII) that uses the damage caused to calculate the scale of the earthquake – it is incredibly quick and easy to evaluate but is a bit vague and could vary between LEDCs and MEDCs.
Case Study – L’Aquilia Earthquake
Case Study – L’Aquilia Earthquake Key Figures 6 th April 2009 – 3.32am (Local Time) 2km North North West (NNW) of Aquilia 6.3 on the Richter Scale Over 300 dead (out of about 70,000) Quite an ancient town – liable to destructions
Case Study – L’Aquilia Earthquake Short Term Impacts About 300 deaths (many more injured) Bridge and water pipe destroyed People in bed Prime Minister cancelled Moscow trip Thousands of buildings damaged, including earthquake-resistant ones and historic buildings
Case Study – L’Aquilia Earthquake Short Term Responses Area declared an emergency zone 30 million euros national funding Camps for the homeless Rescue operation All council tax and bills temporarily suspended, free phones given out
Case Study – L’Aquilia Earthquake Short Term Responses Toll roads became free Sleeping in railway carriages permitted for the homeless Charity operations begun
Case Study – L’Aquilia Earthquake Long Term Impacts Fires caused more damage Aftershocks hampered rescue efforts Landslide
Case Study – L’Aquilia Earthquake Long Term Responses New town built, though Italy originally refused international aid Investigation on building safety 20,000 of the 70,000 that once lived in L’Aquilia were unable to return even 5 years on Earthquake scientists given 6 year prison sentence for manslaughter
Case Study – Sichuan Earthquake
Case Study – Sichuan Earthquake Key Figures 12 th May 2008 – 2.28pm (Local Time) Lasted for 120 seconds 7.9 on the Richter Scale 69,000 people known to have died Estimated cost totalled $75 million
Case Study – Sichuan Earthquake Short Term Impacts About 69,000 people died 5 million buildings collapsed, including chemical plants that spilled toxic ammonia Roads and rivers blocked
Case Study – Sichuan Earthquake Short Term Responses 20 helicopters assigned to rescue efforts immediately after the disaster Troops parachuted Tent, clean water and food supplies given to any survivors
Case Study – Sichuan Earthquake Long Term Impacts 18,000 people still missing two months after the earthquake 5,000,000 homeless Phones cut off (landline and mobile)
Case Study – Sichuan Earthquake Long Term Responses $75 million needed for rescue efforts Help from Japan, Russia and South Korea £100 million donation by the Red Cross 1 million temporary homes built and a $10 million rebuilding fund set aside
Earthquake Comparisons L’AquiliaSichuan 300 dead69,000 dead 30 million euros needed$85 million + £100 million needed Camps and railway carriages provided for the homeless 5,000,000 homeless – had to stay elsewhere Phones handed outAll phone lines destroyed
Factors affecting earthquake effects Magnitude Rural / Urban Population size Building Quality Time of Day MEDC / LEDC Spread of disease Communication links Availability of emergency services
Predicting Earthquakes Parkfield, USA, had a run of earthquakes from the 1800s to the 1960s where a magnitude 6 earthquake hit every 22 years or so. However, the pattern ended when the USGS came to investigate (United States Geological Survey)
Predicting Earthquakes Fence offsets can show tremors Stress built up can be reviewed by instruments Ground can rise by up to 6 metres Predicting the size of the earthquake is particularly crucial
Predicting Earthquakes The Chaos Theory looks at the amount of chaos and mathematical formulas – it has a very high accuracy rate Other mysterious earthquake changes include ground water level, animal behaviour and bright lights in the sky
Predicting Earthquakes Chinese Snakes – In the case of an earthquake, they will try to escape their enclosure or even kill themselves Bright lights in the sky might be caused by small currents in crushed rocks – there might also be electromagnetic pulses
Predicting Earthquakes A key question is whether to put money into a)Predicting earthquakes b)Making the buildings so that they don’t fall down and kill people in the first place
Predicting Earthquakes Earthquake drills are taught At the moment, we have to say no to prediction USGS – Could they make recording systems along the San Andreas Fault to create an early warning system? – This would cost 100 million dollars, but would save 200 billion dollars
The Three Ps – Hazard Management At a glance Prediction – Trying to forecast when an event will happen (volcanoes are easier than earthquakes) Protection – Constructing buildings to meet appropriate safety standards Preparation – Organising drills and codes of practise so that people know what to do in the case of an emergency
The Three Ps – Hazard Management Key Idea The effects of and responses to volcanic eruptions and earthquakes, and how they differ due to contrasts in levels of wealth.
Volcano Prediction Warning SignsMonitoring Techniques Hundreds of small earthquakes as magma rises up through cracks Seismometers are used to detect earthquakes Temperatures increase around the volcano as activity increases Thermal imaging techniques and satellite cameras can detect heat When near to erupting, gas is released, which increases in levels of sulphur as the eruption nears Gas samples and chemical sensors are used to measure sulphur levels
Earthquake Prediction Monitoring of water levels Using seismometers for ground movement Looking at past patterns Strange animal behaviour Rocks with small charge when crushed Monitoring release of radon gas Laser beams across a fault for any small movements
Earthquake Protection Liquefaction is where sediments sink and water rises when earthquakes occur, making anything above the ground (like a house) unstable. This can be prevented by fitting flexible strings down into stiff ground
Earthquake Protection The Transamerica Pyramid in San Francisco is designed to combat the force of an earthquake by changing its shape and being fitted with stability supports amongst other features.
Earthquake Preparation TV / Radio / School Earthquake Drills (using “DROP – COVER – HOLD ON) Roads and Bridges to withstand power Earthquake-proof buildings like “The Transamerica Pyramid” Emergency kits (first-aid items, blankets, tinned food etc.)
Suggestions for Preparation Strap heavy objects to walls Emergency closets – easily accessible Fire extinguishers Roof in a good condition
Scientist Research Scientists have concentrated on protection This is because prediction has been proven to be too difficult to achieve
Why do people stay at risk? This is because volcanic land can be more fertile than others, it may be the only space available and some places may have been established before our knowledge of earthquakes and volcanoes had developed
Tsunamis These are special types of wave caused by water being displaced upwards, generally by an earthquake. They are unlike most other waves, which are caused by the wind.
Indian Ocean Case Study The epicentre of the earthquake was in the Indian Ocean, near Banda Aceh in Indonesia. 220,000 died, 650,000 were injured, 2 million became homeless and people that knew the rescue procedure were killed before they could help.
Indian Ocean Case Study Most fishing boats were destroyed (primary industry), and the area was isolated due to rail/road links damaged. Trees uprooted, drinking water contaminated and salinisation occurred, making the land infertile.
Geography Restless Earth GCSE Revision AQA Unit 1 Section A