Geography the restless earth gcsePresentation Transcript
The Restless Earth Unit 1 : Physical
The Restless Earth• The Earth’s crust is made up from an inner core, outer core, mantle and crust.• The crust is divided by lots of slabs called tectonic plates, (floating on the mantle).• Plates are made up of two types of crust-Continental crust is thicker and less dense than Oceanic which isthinner and more dense.• The plates are moving because the rock in the mantle underneath them is moving.• The places where plates meet are called boundaries, or plate margins.
Plate MarginsDestructive Margins:Where 2 plates are moving towards each other,e.g. along the east coast of Japan and theNazca plate sub-ducting under the SouthAmerican plate.When an oceanic plate (Nazca) and acontinental plate meet, the denser oceanicplate is forced down into the mantle anddestroyed.This often creates volcanoes and oceantrenches (very deep sections of the ocean floorwhere the oceanic plate goes down). Constructive Margins: Are where 2 plates are moving away from each other. e.g. at the mid-Atlantic ridge- Iceland. Magma (molten rock) rises from the mantle to fill the gap and cools, creating new crust.
Conservative MarginsThe San Andreas Fault is an example ofconservative margins. The 2 plates aremoving sideways, past each other, or inthe same direction but one movingfaster than the other.Crust isn’t created or destroyed. Fold Mountains -Fold Mountains are formed on destructive plate margins. -Rivers carry sedimentary rocks such as sandstone and limestone. -They are deposited into depressions. The Himalayas in Asia were formed by -After a few million years the 2 continental plates. sediments are compressed into sedimentary rocks then forced upwards into a series of folds by the movement of tectonic plates. The Andes in S.America were formed by an oceanic and continental plate.
Where the rocks are folded upwards,they are called anticlines. Where therocks are folded downwards, they are Fold Mountainscalled synclines. Severely folded andfaulted rocks are called nappes. • Fold Mountains have very steep slopes which are rocky, often with snow and glaciers in the highest bits and lakes in the valleys between the mountains. Human activity in Fold Mountain Areas: Farming: Higher mountain slopes aren’t great for growing crops, but are for grazing animals such as goats. Sometimes the land is terraced to accommodate crops. Mining: Fold mountains are a 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 (to store water) are 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.
Case Study!• The Alps is a Fold Mountain range, formed around 30 million years ago by the collision of the African and European plates.• Population: 12 million• Farming: Slopes have been terraced for vineyards- Lavaux Switzerland and goats are grazed for cheese, meat and milk• HEP: Switzerland gets 60% of its electricity from HEP stations in the Alps.• Mining: Has declined due to cheaper foreign sources.• Forestry: Scots Pine is planted all over the Alps as it’s more resilient to goats.• Tourism: 100 million tourists per year= huge part of economy. 70% of tourists visit in winter. New villages have been built, e.g. Tignes in France. Adaptations people have made1) Steep relief: Goats are farmed because they’re well adapted to steep mountains. Manmade defences are used to protect against avalanches and rock slides.2) Poor soils: The soil isn’t great for crops, so animals are grazed.3) Limited communications: Brenner Pass between Austria and Italy has been built but snowoften blocks it up and it takes a while to travel along it. So tunnels have been cut through forfast transport links. For example, the Lotschberg Base Tunnel has been cut through theBernese Alps in Switzerland.
Quiz…What are the layers the Earth is made from called?Inner core, outer core, mantle, crustWhat are the 2 types of crust and their differences?Oceanic- thinner and denser andContinental-thicker and less denseHow many types of plate margins are there and what arethey called?DestructiveConstructiveConservative
What happens at the different plate margins and give examples?Destructive- move towards, Nazca plate and S.American and on the east coast of Japan.Constructive- move away from each other, Eurasian and North American (over Iceland-mid Atlanticridge).Conservative- side by side, San Andreas FaultWhere do fold mountains occur and what are they?They occur at destructive plate margins when they collide and fold the sediments upwards.5 Human uses of fold mountains and an example of one?Mining, forestry, tourism, HEP, farmingThe Alps, Himalayas, AndesUsing one example give some facts related to these 5 usesALPSTourism- 70% in winterFarming- Terraced land for vineyards (Lavaux , Switzerland)HEP- 60% OF Swiss electricity from HEP in Alps.Mining- declined due to cheaper foreign sourcesForestry- Scots Pine is planted as it is more resilient to goats and made into furnitureHow have people adapted in the Alps?Steep relief: Goats are farmed and man made defences have been built to protect against avalanchesand rock slidesPoor soils: Crops aren’t grown but more animals are grazedPoor communications: Tunnels have been built to provide fast communication links, e.g. Lotschberg BaseTunnel.
Volcanoes• Are found at destructive AND constructive plate margins.• At destructive plate margins:The denser oceanic plate sub-ducts under the continental plate- creating an ocean trench.Where the oceanic plate is destroyed in the mantle the magma rises through cracks in thecrust called vents.The magma erupts onto the surface (now called lava) forming a volcano.• At constructive plate margins:The magma rises up into the gap created by the plates moving apart, forming a volcano.Some volcanoes also form over parts of the mantle that are really hot (hotspots) e.g. inHawaii.
Types of volcano:• Composite: Made up of layers of ash and lava that have cooled and hardened into layers.• The lava is usually thick and flows slowly. It hardens to form a steep sided volcano.• Example: Mount Fuji, Japan • Shield: Made up of only lava = lava layers. Lava is runny, flows quickly and spreads over a large area. This forms a low, flat volcano. • Example: Mauna Loa, Hawaii • Dome: Made up of only lava, the lava Scientists try and predict volcanic eruptions is thick, flows slowly and hardens by monitoring escaping gas, tiny quickly, forming a steep sided volcano earthquakes and changes in shape and size • Example: Mount Pelée, Caribbean of the volcano.
Case Study!• The Soufriere Hills in Montserrat erupted on June 25th 1997.• 19 killed• 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.
ImpactsPrimary Impacts1) 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. Secondary Impacts 1) Fires destroyed many buildings including local government offices, the police headquarters and the town’s central petrol station. 2) Tourists stayed away and businesses were destroyed disrupting the economy. 3) Population decline- 8000 of the 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.
ResponsesImmediate Responses1) 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 (Montserrat’s an overseas territory of the UK).5) Local emergency services provided support units to search for and rescue survivors.Long-term responses1) 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 setup to try and predict further eruptions.
Supervolcanoes• Are massive volcanoes- only at destructive margins. E.g. Yellowstone National Park- USA.Formation1) Magma rises up through cracks in the crust to form a large magma basin below the surface.The pressure of the magma causes a circular bulge on the surface several kms wide.2) The bulge eventually cracks, creating vents for lava to escape through. The lava erupts out ofthe vents causing earthquakes and sending up gigantic plumes of ash and rock.3) As the magma basin empties, the bulge is no longer supported so it collapses- spewing upmore lava.4) When the eruption’s finished there’s a big crater (called a caldera) left where the bulgecollapsed. Sometimes these get filled with water to form a large lake, e.g. Lake Toba in Indonesia.Characteristics of a supervolcano:-Flat (unlike normal ones which are mountains).-Cover a large area-Have a caldera (normal volcanoes just have a crater atthe top).
Consequences of Supervolcanoes• Thousands of cubic kms of ash, rock and lava will be thrown out with the eruption.• A thick cloud of super heated gas and ash will flow at high speed from the volcano, killing, burning and burying everything it touches.• Everything within 10 miles is destroyed.• Ash shot high into the air will block out sunlight over whole continents.
Where are volcanoes found? Quiz…At destructive and constructive plate margins.Describe how volcanoes are formedDestructive: The denser oceanic plate sub-ducts down into the mantle and isdestroyed, creating an ocean trench. Magma rises through cracks in the crust calledvents. The magma erupts, causing a volcano.Constructive: As the plates move apart the magma rises to fill the gap and a volcanois formed.Name the 3 types of volcanoes, give a description of them and an example.Composite: Made up of layers of lava and ash. Lava is thick and flows slowly. Ithardens to form a steep sided volcano. Mount Fuji in Japan is an example.Shield: Gentle slopes, runny, thin lava. Layers of lava only, low and flat. Example,Mauna Loa Hawaii.Dome: Layers of lava only. Steep sided volcano with thick slowly flowing lava. MountPelée in the Caribbean is an example.
How do scientists try and predict volcanic eruptions?By monitoring escaping gas, changes in size of the volcano and tiny earthquakes.Give an example of a volcanic eruption with dates, people killed and why it exploded.Soufriere Hills in Montserrat erupted on the 25th June 1997 killing 19 people.It erupted when the Atlantic plate which had been pushed into the mantle by the Caribbean plate. Magma rose,forming a pool of magma, the rock above collapsed allowing magma to escape through vents and causing theeruption.Name 3 primary and 3 secondary impacts from this eruption.PRIMARY: Plymouth- the capital city was buried in mud and ash,Schools, hospitals, airports and the port were destroyed,19 people died and 17 were injured,Vegetation and farmland were destroyed, 20 villages were destroyed by pyroclastic flows.SECONDARY: Fires destroyed many building including the police headquarters, businesses were destroyed, due tolack of tourists, there was a population decline- 8000 inhabitants fled to avoid the eruption.Volcanic ash improved soils- more fertile, tourism is now on the rise as tourists see the volcano as an attraction.Name 3 immediate and long-term responses.Immediate: People were evacuated from the south of the island to safer parts in the north, shelters were built tohouse evacuees, the UK provided £17million of emergency aid, temporary infrastructure were built (roads,electricity supplies) and local emergency services provided support to help search and rescue people.Long-term: The Montserrat Volcano Observatory was set up to try and predict eruptions in the future, a risk mapwas created and exclusion zones are in place, the UK provided £41 million to develop the north of the island.Explain the formation of Supervolcanoes and give an example of one.Supervolcanoes are formed when magma rises up through cracks in the crust to form a largemagma basin. The pressure of the magma causes a flat, circular bulge to be created above. Thebulge eventually cracks, creating vents for the lava to escape through and causing earthquakes. Asthe magma basin empties the bulge collapses and a caldera is formed.
Earthquakes• Occur at all 3 types of plate margins.• Are caused by tension that builds up.Destructive margins:Tension builds up when one plate gets stuck as it’smoving down past the other into the mantle.Constructive margins:Tension builds along cracks within the plates as theymove away from each other.Conservative margins:Tension builds up when plates that are grinding past eachother get stuck.
The plates eventually jerk past each other sending out shockwaves(vibrations) = earthquake.The waves spread out from the focus (the point in the Earth where theEarthquake starts).The nearer the focus the waves are the more destructive and strongerthey are.The epicentre is the point on the Earth’s surface straight above thefocus.Earthquakes can be measuredThe Richer Scale: measures the amount ofenergy released (magnitude). (1+ where 5 is major) The Mercalli Scale: measures the effects of an earthquake. (1-12)
Case Study! Rich and poor countries are affected differently by earthquakes.L’Aquila- Italy Kashmir-Pakistan6th April 2009 8th Oct 20056.3 on Richter scale 7.6 on Richter scaleItaly had laws on construction standards No local disaster planning was in placeItaly has a Civil Protection Department- trains volunteers for rescue Buildings were not earthquake proofoperations Primary effects:Primary effects: 80,000 deaths, hundreds of thousands injured290 deaths- collapsed buildings 3 million homelessHundreds injured Water pipelines and electricity supplies were cut offThousands homeless Secondary effects: Landslides buried buildings and peopleSecondary effects: Diseases such as diarrhoea spread due to unclean waterFires caused damage Immediate responses:Broken waterpipe caused landslide Help didn’t reach many areas for days or weeksImmediate responses: People had to be rescued by hand without any help from the emergencyCamps were set up for homeless with medical care servicesCranes and diggers used to remove rubble International aid was given (helicopters and rescue dogs)Money was provided by government Long-term responses:Long-term responses: 40,000 people been relocated to new townsPM promised to build new town Training has been provided to help rebuild more buildings as earthquakeAn investigation to find out why some buildings weren’t earthquake resistantproof. New health centres have been set up
Tsunamis- Case Study! A tsunami is a series of continuous waves caused when huge amounts of water get displacedWest Coast of Indonesia/ Indian Ocean26th December 20049.1 Richter ScaleWaves 30m high :OIndonesia, India, Thailand and Sri Lanka were the worst affected.There was NO EARLY WARNING SYSTEM-230,000 people were killed-Whole towns and villages were destroyed- 1.7 million lost their homes-Infrastructure (roads, waterpipes electricity lines) were severely damaged-5-6 million people needed emergency food, water and medical supplies-Economic damage: fisherman lost livelihoods and tourism plummeted because of total destruction + afraid of it repeating-Environmental damage: salt from sea all over plants prevented growthShort-term responses:1) Hundreds of millions of pounds had been pledged by foreign govs, charities to give survivors food, water, shelter, medical attention2) Foreign countries sent ships, planes and soldiers to help rescue people, distribute food and help clear messLong-term responses:1) Billions of pounds pledged to help re-build2) Programmes set up to help people get back to work3) A tsunami warning system has been put in place in the Indian Ocean4) Disaster Management Plans have been put in place in some countries5) Volunteers have been trained for future tsunamis