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The Restless Earth Year 11 revision. Key terms. Key terms. Key terms. Key terms. Key facts : Structure of the Earth. Key facts : The crust. Continental Crust On land Thicker (30-65km) LIGHT Granitic rock ( rich in Si, Al ). Oceanic Crust Underneath oceans/seas
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Key facts: The crust • Continental Crust • On land • Thicker(30-65km) • LIGHT Granitic rock • (rich in Si, Al) • Oceanic Crust • Underneath oceans/seas • Thinner (8-12km) • HEAVY Basaltic rock • (rich in Si, Mg) Mantle
Key facts: Constructive plate boundary Plates are pulled apart by the convection currents in the mantle below Magma rises between the plates, forming volcanoes Eurasian Plate North American plate e.g. The mid-Atlantic Ridge (Eurasian and North American plates moving apart)
Key facts: Destructive plate boundary 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 earthquakes Heavier oceanic crust gets pushed under the continental plate e.g. Nazca is subducting under South American plate. Lower mantle The area where the oceanic plate sinks below the continental plate is called the SUBDUCTION ZONE
Key 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.
Key facts: Collision plate boundary 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 Two continental crusts move towards each other
Key facts: Hazards at plate margins Asia North America Europe Africa South America Australasia 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: • 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: • 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: • 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 Name: San Francisco, USA (MEDC) Date: 17th 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 San Andreas Fault
Earthquake Case Study 1: • 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: 13th January and 13th 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: • 13th January earthquake: • 844 fatalities, 4,723 injured, 108,226 houses destroyed • Many of the fatalities and much of the damage was caused by landslides • 13th 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
Preparing for earthquakes and volcanoes • Monitoring seismic waves • Earthquake proof buildings • ‘Grab bags’ containing essential items e.g. Tinned food, bottled water, blanket • Training emergency services • Evacuation plans • Early warning systems Aims: Minimise loss of life Minimise disruption of critical services Minimise damage
Video revision: • Continental drift • So why do the plates move? • Structure of the Earth 1 • Structure of the Earth 2 • Why do volcanoes & earthquakes happen? • Volcano formation • Subduction • Shield volcano • Mt St Helens • Nyiragongo film
Past GCSE questions: A • Describe 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)
Past GCSE questions: B Describe 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)
Past GCSE questions: C Describe 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)
