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Restless Earth Revision Revise the topic Practice exam technique Draw Get into groups of four and number yourselves. Draw your plate boundary: 1. destructive 2. collision 3. constructive 2 minutes 4. conservative Practice drawing these diagrams. Use them in the exam. Review and Rate • Read the summary of the topic. • Rate each section: how confident do you feel with each part? The Earth’s Structure Earth’s interior has a layered structure, with different composition and physical properties. Interpreting a cross-section of the Earth, with details (temperature, density, composition, physical state) of layered structure (including the asthenosphere) Different types of crust. Contrast continental and oceanic crust. OCEANIC This is heavy (density of 3.0), made of Minerals rich in Iron and Magnesium Is about 6-10 km thick on average and is usually under 200 million years old. CONTINENTAL This is lighter (density of 2.6), made of minerals rich in silica and aluminium, is about 30-70km thick and is mainly over 1500 million years old. Convection Currents Plumes of heat rise in the mantle Convection cell in the mantle Crust Solid Convection in the liquid outer core Earth’s Tectonic Plates and their Boundaries Mapping the distribution of the three plate margin types, and naming major plates. or Types of Volcano A shield volcano A composite or stratovolcano e.g. Mauna Loa, Hawaii Very hot, runny, basaltic lava. Eruptions rarely violent. Thick, viscous, andesitic lava. Explosive eruptions. e.g. Mount Pinatubo, Philippines Earthquake Hazards Contrasting earthquake effects in named locations Impacts on property versus people. Loma Prieta earthquake, USA • Date: Tuesday 17 October 1989, at 17.04 • Magnitude: 6.9 on the Richter Scale • Epicentre: in a mountainous part of Santa Cruz County, 90 km south-east of San Francisco • Death toll: 63 • Injured: 3,757 • Homeless: 12,000 • Property cost: $10 billion Kashmir, Pakistan • Date: Saturday 8 October 2005 • Magnitude: 7.6 on the Richter Scale • Epicentre: Muzaffarabad, the capital of Pakistaniadministered Kashmir • Death toll: 75,000 • Injured: 75,000 • Homeless: 2.8 million • Property cost: $440 million Impacts worst on property in developed countries. Impacts worst on people in developing countries. Contrasting economic and social volcanic hazard impacts Mount St Helens, USA • Date: Sunday 18th May 1980 at 8.33 am. • Magnitude: 5 on the Volcanic Explosivity Index 5 (paroxysmal). • Homes destroyed: 200 • Death toll: 61 (most as a result of poisonous gases which accompanied the blast). • Evacuated: 2,000 people • Property cost: $1.1 billion. Economic impacts worse in developed countries. Mount Nyiragongo, DR Congo • Date: 17th January 2002. • Magnitude: Gentle; 1 on the Volcanic Explosivity Index (VEI). • Homes destroyed: 12,500 • Death toll: 100 (mostly from poisonous gas and getting trapped in lava). • Evacuated: 400,000 • Lava: hot, runny, basaltic • Homeless: 120,000 Social impacts worse in developing countries. Predicting Earthquakes • Earthquakes are not as easy to predict as volcanic eruptions. However, there are still some ways of monitoring the chances of an earthquake: • Laser beams can be used to detect plate movement. • A seismometer is used to pick up the vibrations in the Earth's crust. An increase in vibrations may indicate a possible earthquake. • Radon gas escapes from cracks in the Earth's crust. Levels of radon gas can be monitored - a sudden increase may suggest an earthquake. Preparing for Earthquakes • People living in earthquake zones need to know what they should do in the event of a quake. Training people my involve holding earthquake drills and educating people via TV or radio. • People may put together emergency kits and store them in their homes. An emergency kit may include first-aid items, blankets and tinned food. • Earthquake proof buildings have been constructed in many major cities, eg The Transamerica Pyramid in San Francisco. Buildings such as this are designed to absorb the energy of an earthquake and to withstand the movement of the Earth. • Roads and bridges can also be designed to withstand the power of earthquakes. Earthquake-proof building design Developed country Developing country Predicting Volcanic Eruptions Warning signs Monitoring techniques Hundreds of small earthquakes are caused as magma rises up through cracks in the Earth's crust. Seismometers are used to detect earthquakes. Temperatures around the volcano rise as activity increases. Thermal imaging techniques and satellite cameras can be used to detect heat around a volcano. When a volcano is close to erupting Gas samples may be taken and it starts to release gases. The chemical sensors used to higher the sulfur content of these measure sulphur levels. gases, the closer the volcano is to erupting. Predicting and Preparing for Volcanic Eruptions Preparing for Volcanic Eruptions • Creating an exclusion zone around the volcano. • Being ready and able to evacuate residents. • Having an emergency supply of basic provisions, such as food. • Funds need to be available to deal with the emergency and a good communication system needs to be in place. Haiti, 2010 Impacts Response Problems Death toll: 200,000 (estimated) Homeless: 1.5 million (estimated) Tens of thousands without food, water and medical supplies Port-au-Prince port badly damaged US took control of Port-au-Prince airport UN World Food Programme increased food aid to survivors, e.g. 2 million meals delivered on one day US carried out air drops The Haitian authorities were not prepared for the earthquake Port-au-Prince airport has limited capacity Lack of fuel Glossary • You need to be familiar with these words so that you can: – understand what questions mean (easier) – define them (harder) • Use the glossary sheet as a check list. Tick them off once when you when you understand them and again when you can define them. • Concentrate at first on the terms in bold. Exam question (a) Identify one advantage and one disadvantage that Sakurajima has brought to Japan. (2) (b) Explain one reason way in which the impact of a volcanic eruption might be different in a less developed country. (2) • More deaths/greater impacts on people. Accept other reasonable suggestions. • Explanation: • People more likely to live in risky locations • Can’t afford safe, well-built houses so buildings often collapse • Communications poor, so warning and evacuation may not happen (so effectively) • Poverty • Slow/inadequate relief effort may lead to lack of shelter, clean water and food. Disease may spread • Governments don’t have the money or resources to provide aid (c) Using examples, explain how eruptions can be predicted. (4) (c) Using examples, explain how eruptions can be predicted. (4) Warning signs Monitoring techniques Hundreds of small earthquakes are caused as magma rises up through cracks in the Earth's crust. Seismometers are used to detect earthquakes. Temperatures around the volcano rise as activity increases. Thermal imaging techniques and satellite cameras can be used to detect heat around a volcano. When a volcano is close to erupting Gas samples may be taken and it starts to release gases. The chemical sensors used to higher the sulfur content of these measure sulphur levels. gases, the closer the volcano is to erupting.