Presentation on theme: "The Restless Earth Year 11 revision. Key terms Key termDefinition AsthenosphereThe upper part of the Earth’s mantle, where the rocks are more fluid. Collision."— Presentation transcript:
The Restless Earth Year 11 revision
Key terms Key termDefinition AsthenosphereThe upper part of the Earth’s mantle, where the rocks are more fluid. Collision plate boundary A tectonic margin at which two continental plates come together (collide). Conservative plate boundary Where two tectonic plates slide past each other. Constructive plate boundary Tectonic plate margin where rising magma adds new material to the diverging plates. Destructive plate boundary Tectonic plate margins where oceanic plate is subducted. Convection currents Circulating movements of magma in the mantle caused by heat from the core.
Key terms Key termDefinition CoreThe 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 planning Planning 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 crust The part of the crust dominated by less dense granitic rocks. (Under continents)
Key terms Key termDefinition 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 impacts Impacts caused directly by the volcano/earthquake. Secondary impacts Impacts 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 relief Help and aid provided to an area to prevent immediate loss of life because of shortages of basics, such as water, food and shelter.
Key terms Key termDefinition FocusThe 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.
Key facts: Structure of the Earth
Key facts: The crust Oceanic Crust Underneath oceans/seas Thinner (8-12km) HEAVY Basaltic rock (rich in Si, Mg) Continental Crust On land Thicker (30-65km) LIGHT Granitic rock (rich in Si, Al) Mantle
Key facts: Tectonic plates
Key facts: Constructive plate boundary Plates are pulled apart by the convection currents in the mantle below Magma rises between the plates, forming volcanoes North American plate Eurasian Plate e.g. The mid-Atlantic Ridge (Eurasian and North American plates moving apart)
Key facts: Destructive plate boundary Lower mantle Heavier oceanic crust gets pushed under the continental plate The rock jolts and grinds, causing earthquakes The movement heats up the rock and melts it. The molten rock forces its way up through the crust to form a volcano. The area where the oceanic plate sinks below the continental plate is called the SUBDUCTION ZONE e.g. Nazca is subducting under South American plate.
Key facts: Conservative plate boundary 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. e.g. San Andreaas Fault in California, USA. (North American and Pacific plates sliding past each other)
Key facts: Collision plate boundary Two continental crusts move towards each other The plates neither sink or are destroyed – so they buckle upwards forming mountains The rock jolts and grinds, causing earthquakes e.g. The Himalayas (Nepal). Formed as the Indian and Eurasian continental plates push into each other
Africa North America South America Europe Australasia Asia Key facts: Hazards at plate margins Key: Volcano Earthquake
Key facts: Convection currents Circulating movements of magma in the mantle (convection currents) caused by heat from the core
Volcano Case Study 1: Type: Composite volcano Name: Mt St. Helens, USA
Volcano Case Study 1: TypeComposite volcano NameMt 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 flows Highly explosive with lots of boulders and debris. Nuée ardente (hot ash and gas), Lahars (mudflows of ash and water).
Volcano Case Study 1: Mount Saint Helens Date: 18 th May 1980 Type: Composite volcano Primary effects:Secondary effects 57 fatalities, 200 houses, 27 bridges, 15 miles of railway and 185 miles of roads were destroyed Ash cloud reached 80,000ft in 15 minutes, circled the earth in 15 days The eruption removed 13% of the volcano’s rock, making it 390m shorter Thousands of Elk, Deer and Salmon were killed and crops were destroyed Major problems with sewerage disposal and water systems Roads closed due to low visibility from the ash Some airports closed for two weeks Fine ash getting into electrical systems caused blackouts 5 further eruptions between May and October 1980
Volcano Case Study 2: Type: Composite/Fissure volcano Name: Mt Nyiragongo.
Volcano Case Study 2: Type Composite/Fissure volcano NameMt Nyiragongo LocationDemocratic 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 quickly Explosivity/ pyroclastic flows Low explosivity but fast-moving lava poses great danger. CO 2 gas released. Ash clouds occur.
Volcano Case Study 2: Mt Nyiragongo, Democratic Republic of Congo Date: 17 th January 2002 Type: Composite / Fissure volcano Primary effects:Secondary effects Homes were destroyed by ash and lava 100 people died Lava filled roads making it difficult for emergency services to move around Lava covered 15% of Goma city, and destroyed 30% of the city 400,000 people evacuated Cholera spread because of poor sanitation One month after the eruption, 350,000 people were dependant on aid People lost their businesses and jobs After the eruption, a large number of earthquakes were felt around Goma and Gisenyi
Volcano Case Study 3: Type: Shield volcano Name: Mauna Loa, Hawaii.
Volcano Case Study 3: Type Shield volcano NameMauna Loa LocationHawaii (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 shape Explosivity/ pyroclastic flows Low, non-explosive.
Volcano Case Study 3: Mauna Loa, Hawaii Date: 24 th March, 1984 Type: Shield volcano Primary effects:Secondary effects Potential impact to the city of Hilo, though lava from the 1984 eruption did not impact the city In the 1950 eruption, lava reached the sea within 4 hours of the eruption and destroyed a village There has only been one recorded fatality from eruptions of Mauna Loa
Earthquake Case Study 1: San Francisco San Andreas Fault Name: San Francisco, USA (MEDC) Date: 17 th October, 1989 Why: California sits near the San Andreas fault The Pacific and North American plates slide past each other The fault slipped several metres
Earthquake Case Study 1: San Francisco Facts 63 dead Clay soils liquefied, causing houses to sink, gas pipes to burst fires broke out Nearly 4,000 injured Hit during rush hour Death 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 homeless Property cost $10 billion
Earthquake Case Study 1: San Francisco, USA Size: 6.9 on Richter Scale Primary effects:Secondary effects 63 fatalities, 3,757 injuries and 12,000 homeless Upper deck of Freeway collapsed onto lower deck, causing 42 fatalities 1.4 million people without power following the earthquake, restored to most the same day Burst gas mains leading to multiple fires Soil liquefaction causing major property damage Landslides and ground ruptures 1.4 million people without power following the earthquake
Earthquake Case Study 2: Name: El Salvador, Central America (LEDC) Date: 13 th January and 13 th February, 2001 Facts: Smallest country in Central America with less people than London. Very seismically active area, at the junction of three tectonic plates What happened?: Two major earthquakes within 1 month, plus thousands of aftershocks
Earthquake Case Study 2: Facts Emergency 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 LEDC Less equipment/ training for emergency services (LEDC) so response effectiveness reduced. 185,338 houses damaged Over 8,000 injuries Buildings and roads are not usually designed to withstand earthquakes here >1.5million people affected Even where fire-engines are available there is no water supply for them to use or good roads to reach the areas in need.
Earthquake Case Study 2: El Salvador, Central America Size: 7.6 / 6.6 on Richter Scale Primary effects:Secondary effects 13 th January earthquake: 844 fatalities, 4,723 injured, 108,226 houses destroyed Many of the fatalities and much of the damage was caused by landslides 13 th February earthquake: 315 fatalities, 3,399 injured, 41,302 houses destroyed More than 2,500 aftershocks, causing additional damage More than 500 landslides Clean water and sanitation became major issues Major disruption to electricity supplies Damage to the telephone system and the control tower at the airport delayed incoming relief from abroad
What factors influence the effects / impacts of a hazard? The type of hazard The place’s vulnerability to hazards The ability or ‘capacity’ to cope and recover from an event
Impacts of earthquakes FactorWhy this affects the impact of an earthquake? Distance from the epicentre The 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 climate Influences survival rates and the rate at which disease can spread.
Preparing for earthquakes and volcanoes 1.Monitoring seismic waves 2.Earthquake proof buildings 3.‘Grab bags’ containing essential items e.g. Tinned food, bottled water, blanket 4.Training emergency services 5.Evacuation plans 6.Early warning systems Aims: a)Minimise loss of life b)Minimise disruption of critical services c)Minimise damage
Preparing 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 skyscrapers Gas and water lines specially reinforced with flexible joints to prevent breaking
Preparing for earthquakes and volcanoes LEDC building design: Strengthening new buildings by: - Removal of mud overlay on roof - Add 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 level - Pointing of exterior walls with cement mortar LEDC building design: Strengthening old buildings by: - Use cement/sand mortar and shaped stones in construction. - Limit thickness of mud overlay to 200mm - Install ‘knee-braces’ to reinforce the vertical/horizontal connections - Use straw roofs
Long and short-term responses to tectonic hazards Short-term responseLong-term response Emergency careDamage proof buildings Foreign/national aidEducation/training Prepare emergency kits for future quakes/eruptions Permanent relocation Evacuation procedures in place Evacuation plans and websites to inform citizens
Goals of disaster management Reduce, or avoid, losses from hazards. Achieve rapid and effective recovery. Assure prompt assistance to victims.
Video revision: 1.Continental driftContinental drift 2.So why do the plates move?So why do the plates move? 3.Structure of the Earth 1Structure of the Earth 1 4.Structure of the Earth 2Structure of the Earth 2 5.Why do volcanoes & earthquakes happen?Why do volcanoes & earthquakes happen? 6.Volcano formationVolcano formation 7.SubductionSubduction 8.Shield volcanoShield volcano 9.Mt St HelensMt St Helens 10.Nyiragongo filmNyiragongo film
1.Describe one way a region affected by earthquakes can prepare for this hazard. (2 marks) 2.Using an example(s), describe the effects of earthquakes on people and property. (4 marks) 3.Suggest one reason why the number of deaths varies between earthquakes. (2 marks) 4.Give two reasons why developing countries are very vulnerable to earthquake damage (2 marks) 5.Give two reasons why some earthquakes are more powerful than others (2 marks) 6.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) Past GCSE questions: A
Past GCSE questions: B 7.Describe how hazard resistant design can help reduce the impact of earthquakes (4 marks) 8.Explain how building design can help reduce the impact of earthquakes (4 marks) 9.Explain how earthquakes happen on destructive plate margins (4 marks) 10.Explain how volcanoes are formed on either constructive or destructive plate boundaries. (4 marks). 11.For a named volcanic event, compare the primary and secondary impacts (6 marks)
Past GCSE questions: C 12.Describe two hazards volcanic eruptions can create for people (4 marks) 13.Explain how shield volcanoes are formed. (4 marks) 14.Describe the features of a shield volcano (2 marks) 15.Examine why the characteristics of volcanoes vary (6 marks) 16.Outline one difference between oceanic and continental crust (2 marks) 17.Describe two differences between oceanic and continental crusts (4 marks) 18.Draw an accurate labelled diagram of a destructive plate margin (4 marks)