2Key terms Key term Definition Asthenosphere The upper part of the Earth’s mantle, where the rocks are more fluid.Collision plate boundaryA tectonic margin at which two continental plates come together (collide).Conservative plate boundaryWhere two tectonic plates slide past each other.Constructive plate boundaryTectonic plate margin where rising magma adds new material to the diverging plates.Destructive plate boundaryTectonic plate margins where oceanic plate is subducted.Convection currentsCirculating movements of magma in the mantle caused by heat from the core.
3Key terms Key term Definition Core The central part of the Earth, consisting of a solid inner core and a more fluid outer core, and mostly composed of iron and nickel.EvacuationThe removal of people from an area, generally in an attempt to avoid a threatened disaster (or escape from one that has happened).Long-term planningPlanning that takes into consideration the long term (i.e. over 5 years).Oceanic crustThe part of the crust dominated by denser basaltic rocks. (Under oceans)Continental crustThe part of the crust dominated by less dense granitic rocks. (Under continents)
4Key terms Key term Definition Tectonic hazards Threats posed by earthquakes, volcanoes and other events triggered by crustal processes.Plate marginThe boundary between two tectonic plates.PredictionForecasting future changes.Primary impactsImpacts caused directly by the volcano/earthquake.Secondary impactsImpacts caused indirectly by the volcano/earthquake, for example ‘a knock on effect’ e.g. Fires caused by broken gas pipes.ResponseThe way and which people react to a situation.Short-term emergency reliefHelp and aid provided to an area to prevent immediate loss of life because of shortages of basics, such as water, food and shelter.
5Key terms Key term Definition Focus The point inside the earth where an earthquake starts.EpicenterThe point on the lands’ surface, directly above the focus.Seismic wavesWaves of energy that radiate out from an earthquake.MagnitudeThe size of an earthquake, measured by the Richter Scale.
7Key facts: The crust Continental Crust Oceanic Crust On land Thicker (30-65km)LIGHT Granitic rock(rich in Si, Al)Oceanic CrustUnderneath oceans/seasThinner (8-12km)HEAVY Basaltic rock(rich in Si, Mg)Mantle
9Key facts: Constructive plate boundary Plates are pulled apart by the convection currents in the mantle belowMagma rises between the plates, forming volcanoesNorth American plateEurasian Platee.g. The mid-Atlantic Ridge (Eurasian and North American plates moving apart)
10Key facts: Destructive plate boundary Heavier oceanic crust gets pushed under the continental platee.g. Nazca is subducting under South American plate.The movement heats up the rock and melts it. The molten rock forces its way up through the crust to form a volcano.The rock jolts and grinds, causing earthquakesLower mantleThe area where the oceanic plate sinks below the continental plate is called the SUBDUCTION ZONE
11Key facts: Conservative plate boundary e.g. San Andreaas Fault in California, USA. (North American and Pacific plates sliding past each other)Plates slide past each other. Parts of the plates get stuck and then lurch free causing earthquakes.No rock is pushed down or melted and no gaps occur between the plates therefore there are no volcanoes.
12Key facts: Collision plate boundary The plates neither sink orare destroyed – so they buckleupwards forming mountainsThe rock jolts and grinds, causing earthquakese.g. The Himalayas (Nepal). Formed as the Indian and Eurasian continental plates push into each otherTwo continental crustsmove towards each other
13Key facts: Hazards at plate margins AsiaNorth AmericaEuropeAfricaSouth AmericaAustralasiaKey:VolcanoEarthquake
14Key facts: Convection currents Circulating movements of magma in the mantle (convection currents) caused by heat from the core
16Volcano Case Study 1:Type: Composite volcano Name: Mt St. Helens, USA
17Volcano Case Study 1: Type Composite volcano Name Mt St. Helens LocationWashington State, USA. On the plate boundary between the Juan de Fuca plate and North American plate.FormationLayers of lava and ash are deposited by eruptions. The lava is....Lava type...mostly andesitic, which typically cools and hardens before spreading far due to high viscosity (thick like honey!), leading to...Shape...a steep-sided volcano.Explosivity/ pyroclastic flowsHighly explosive with lots of boulders and debris. Nuée ardente (hot ash and gas), Lahars (mudflows of ash and water).
18Type: Composite volcano Volcano Case Study 1:Mount Saint HelensDate: 18th May 1980Type: Composite volcanoPrimary effects:Secondary effects57 fatalities, 200 houses, 27 bridges, 15 miles of railway and 185 miles of roads were destroyedAsh cloud reached 80,000ft in 15 minutes, circled the earth in 15 daysThe eruption removed 13% of the volcano’s rock, making it 390m shorterThousands of Elk, Deer and Salmon were killed and crops were destroyedMajor problems with sewerage disposal and water systemsRoads closed due to low visibility from the ashSome airports closed for two weeksFine ash getting into electrical systems caused blackouts5 further eruptions between May and October 1980
19Volcano Case Study 2:Type: Composite/Fissure volcano Name: Mt Nyiragongo.
20Volcano Case Study 2: Composite/Fissure volcano Type Name Mt NyiragongoLocationDemocratic Republic of Congo (Africa)FormationLayers of lava have erupted from the crater and fissures. The lava...Lava type...has an extremely low silica content (the lava is mafic) and so flows very fast (can reach 100km/h), meaning...Shape...the volcano has very steep sides as the lava flows away so quicklyExplosivity/ pyroclastic flowsLow explosivity but fast-moving lava poses great danger. CO2 gas released. Ash clouds occur.
21Volcano Case Study 2: Mt Nyiragongo, Democratic Republic of Congo Date: 17th January 2002Type: Composite / Fissure volcanoPrimary effects:Secondary effectsHomes were destroyed by ash and lava100 people diedLava filled roads making it difficult for emergency services to move aroundLava covered 15% of Goma city, and destroyed 30% of the city400,000 people evacuatedCholera spread because of poor sanitationOne month after the eruption, 350,000 people were dependant on aidPeople lost their businesses and jobsAfter the eruption, a large number of earthquakes were felt around Goma and Gisenyi
22Volcano Case Study 3:Type: Shield volcano Name: Mauna Loa, Hawaii.
23Volcano Case Study 3: Shield volcano Type Name Mauna Loa Location Hawaii (on the ‘Hawaii Hotspot’)FormationMauna Loa was created as the Pacific tectonic plate moved over the Hawaiian hotspot in the mantle. Fluid lava flows out slowly from the volcano because...Lava type...the lava is mostly basaltic, silica-poor, and very fluid. This creates...Shape...a low and flat shapeExplosivity/ pyroclastic flowsLow, non-explosive.
24Volcano Case Study 3: Mauna Loa, Hawaii Date: 24th March, 1984 Type: Shield volcanoPrimary effects:Secondary effectsPotential impact to the city of Hilo, though lava from the 1984 eruption did not impact the cityIn the 1950 eruption, lava reached the sea within 4 hours of the eruption and destroyed a villageThere has only been one recorded fatality from eruptions of Mauna Loa
26Earthquake Case Study 1: San Francisco Name: San Francisco, USA (MEDC)Date: 17th October, 1989Why:California sits near the San Andreas faultThe Pacific and North American plates slide past each otherThe fault slipped several metresSan Andreas Fault
27Earthquake Case Study 1: San Francisco Facts63 deadClay soils liquefied, causing houses to sink, gas pipes to burst fires broke outNearly 4,000 injuredHit during rush hourDeath toll would have been larger, but 2 big baseball teams playing so many people where at the stadium or already at home, not commuting.12,000 homelessProperty cost $10 billion
28Earthquake Case Study 1: San Francisco, USASize: 6.9 on Richter ScalePrimary effects:Secondary effects63 fatalities, 3,757 injuries and 12,000 homelessUpper deck of Freeway collapsed onto lower deck, causing 42 fatalities1.4 million people without power following the earthquake, restored to most the same dayBurst gas mains leading to multiple firesSoil liquefaction causing major property damageLandslides and ground ruptures1.4 million people without power following the earthquake
29Earthquake Case Study 2: Name: El Salvador, Central America (LEDC)Date: 13th January and 13th February, 2001Facts:Smallest country in Central America with less people than London.Very seismically active area, at the junction of three tectonic platesWhat happened?:Two major earthquakes within 1 month, plus thousands of aftershocks
30Earthquake Case Study 2: FactsEmergency services, such as hospitals and the fire service, are not well-prepared to deal with a large-scale disaster.Roads and other infrastructure poor (as LEDC)El Salvador is a very poor LEDCLess equipment/ training for emergency services (LEDC) so response effectiveness reduced.185,338 houses damagedOver 8,000 injuriesBuildings and roads are not usually designed to withstand earthquakes here>1.5million people affectedEven where fire-engines are available there is no water supply for them to use or good roads to reach the areas in need.
31Earthquake Case Study 2: El Salvador, Central AmericaSize: 7.6 / 6.6 on Richter ScalePrimary effects:Secondary effects13th January earthquake:844 fatalities, 4,723 injured, 108,226 houses destroyedMany of the fatalities and much of the damage was caused by landslides13th February earthquake:315 fatalities, 3,399 injured, 41,302 houses destroyedMore than 2,500 aftershocks, causing additional damageMore than 500 landslidesClean water and sanitation became major issuesMajor disruption to electricity suppliesDamage to the telephone system and the control tower at the airport delayed incoming relief from abroad
32What factors influence the effects / impacts of a hazard? The type of hazardThe place’s vulnerability to hazardsThe ability or ‘capacity’ to cope and recover from an event
33Impacts of earthquakes FactorWhy this affects the impact of an earthquake?Distance from the epicentreThe effects of an earthquake are more severe at its centre.Size of quakeThe higher on the Richter scale, the more severe the earthquake is.Level of development (MEDC or LEDC)MEDCs are more likely to have the resources and technology for monitoring, prediction and response.Population density (rural or urban area)The more densely populated an area, the more likely there are to be deaths and casualties.CommunicationAccessibility for rescue teams.Time of dayInfluences whether people are in their homes, at work or travelling. A severe earthquake at rush hour in a densely populated urban area could have devastating effects.The time of year and climateInfluences survival rates and the rate at which disease can spread.
34Preparing for earthquakes and volcanoes Monitoring seismic wavesEarthquake proof buildings‘Grab bags’ containing essential items e.g. Tinned food, bottled water, blanketTraining emergency servicesEvacuation plansEarly warning systemsAims:Minimise loss of lifeMinimise disruption of critical servicesMinimise damage
35Preparing for earthquakes and volcanoes MEDC building design:Bolting buildings to foundations and providing support walls (‘shear walls’). These are made from concrete and have steel rods embedded inside to help strengthen.Walls reinforced and supported by adding diagonal steel beams (‘cross bracing’)‘Base isolators’ act like shock absorbers between building and foundations. Help absorb some of sideways motion.Deep foundations for skyscrapersGas and water lines specially reinforced with flexible joints to prevent breaking
36Preparing for earthquakes and volcanoes LEDC building design:Strengthening new buildings by:Removal of mud overlay on roofAdd diagonal bracing to frame (often timber as steel too expensive)install ‘through-stones’. Needs training of local artisans (new skills)strengthening of wall corners, using wire mesh and cement overlay (although mesh not often available in rural areas)install ring beam (band of concrete) at roof levelPointing of exterior walls with cement mortarLEDC building design:Strengthening old buildings by:Use cement/sand mortar and shaped stones in construction.Limit thickness of mud overlay to 200mmInstall ‘knee-braces’ to reinforce the vertical/horizontal connectionsUse straw roofs
37Long and short-term responses to tectonic hazards Long-term responseEmergency careDamage proof buildingsForeign/national aidEducation/trainingPrepare emergency kits for future quakes/eruptionsPermanent relocationEvacuation procedures in placeEvacuation plans and websites to inform citizens
38Goals of disaster management Reduce, or avoid, losses from hazards.Achieve rapid and effective recovery.Assure prompt assistance to victims.
39Video revision: Continental drift So why do the plates move? Structure of the Earth 1Structure of the Earth 2Why do volcanoes & earthquakes happen?Volcano formationSubductionShield volcanoMt St HelensNyiragongo film
40Past GCSE questions: ADescribe one way a region affected by earthquakes can prepare for this hazard. (2 marks)Using an example(s), describe the effects of earthquakes on people and property. (4 marks)Suggest one reason why the number of deaths varies between earthquakes. (2 marks)Give two reasons why developing countries are very vulnerable to earthquake damage (2 marks)Give two reasons why some earthquakes are more powerful than others (2 marks)For either an earthquake or a volcanic eruption you have studied, describe the immediate responses (straight after the earthquake) in managing its impact. (4 marks)
41Past GCSE questions: BDescribe how hazard resistant design can help reduce the impact of earthquakes (4 marks)Explain how building design can help reduce the impact of earthquakes (4 marks)Explain how earthquakes happen on destructive plate margins (4 marks)Explain how volcanoes are formed on either constructive or destructive plate boundaries. (4 marks).For a named volcanic event, compare the primary and secondary impacts (6 marks)
42Past GCSE questions: CDescribe two hazards volcanic eruptions can create for people (4 marks)Explain how shield volcanoes are formed. (4 marks)Describe the features of a shield volcano (2 marks)Examine why the characteristics of volcanoes vary (6 marks)Outline one difference between oceanic and continental crust (2 marks)Describe two differences between oceanic and continental crusts (4 marks)Draw an accurate labelled diagram of a destructive plate margin (4 marks)