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What are natural hazards? Natural hazards are natural events that cause loss of live and property. Tectonic hazards are earthquakes and volcanoes. Atmospheric hazards are tropical storms and floods. What affects hazard risk? The hazard risk is the chance that people will be affected by a hazard. Hazard risk depends on three factors: 1. Population density: densely populated areas (such as cities) are worse affected than sparsely populated ones 2. Level of development: HICs have the wealth, technology and infrastructure to cope better than an LIC; and 3. Magnitude of the hazard: Strong earthquakes and storms and grey eruptions cause more damage than weak earthquakes and storms and red eruptions. Structure of the Earth The Earth has four layers: the core (divided into inner and outer), mantle and crust. The crust is split into huge pieces called tectonic plates. There are two types of crust: • Oceanic, which is thin but dense (heavy) and made of basalt; and • Continental, which is thick but light and made of granite. These plates move due to: 1. Convection currents in the mantle causing friction with the plate which pulls it along; and 2. Ridge push and slab pull These are where the weight of a plate at an ocean ridge pushes, or at an ocean trench pulls, the plate down. Where plates meet is called a plate margin: Composite volcano Ocean trench Continental plate Oceanic plate Subduction zone Mantle Primary – earthquakes • • Houses are destroyed, so… Schools are destroyed, so… Gas pipes crack and leak gas, so… Water pipes crack and leak, so… Sewage pipes crack, so… Factories and ports are wrecked, so. . . The seabed jolts up, so… • • • Ash smothers crops, so… Ash acidifies lakes, so… Rocks and ash build up on roofs, so… SO 2 droplets form a ‘veil’ high up, so… Lahars engulf buildings, so… Lava/ash destroys habitats, so… Convection currents 1. Plates move apart. 2. Magma rises up to fill the gap. 3. Creating new ocean bed, shield volcanoes and volcanic islands. Example: Iceland, Mid. Atlantic Ridge. Run away or get to high ground Search for survivors Treat the injured Turn off the gas supply Set up homeless shelters Set up field hospitals Location People are homeless Children’s education suffers Fires burn Fires can’t be put out. Diseases (like cholera) spread The country’s economy suffers A tsunami is created • • • Food shortages or starvation occurs Water supplies poisoned, fish killed Buildings collapse with further effects A volcanic winter occurs (temp drops) People become homeless Wildlife populations suffer Magnitude 7. 0 on the Richter Scale 6. 2 on the Richter Scale Tectonic background (in both examples, the sliding plates create friction which creates earthquakes) Conservative plate margin: the Gonâve Microplate slides past the Caribbean Plate along a transform fault. Secondary – volcanoes Primary effects cause… Destructive plate margin: the Tyrrhenian Plate is being subducted under the Adriatic Plate. …Secondary effects Primary effects cause… …Secondary effects A. 240, 000 houses dest- Ø So 1. 5 m people A. Thousands of houses Ø So 4, 500 people B. 220, 000 people died Ø So bodies rotted in the B. 296 people died and Ø So hospitals struggled C. 4000 schools Ø So children’s education C. Schools were Ø So children’s education royed (shanty towns) destroyed became homeless sun polluting water suffered destroyed 1000 s were injured became homeless to cope destroyed suffered Immediate (short-term) responses Long-term • • • Rebuild houses, hospitals and schools Prioritise sustainable redevelopment Prioritise high-value exports Promote tourism to the area Hold an enquiry into the destruction Improve building standards • Refugee camps and temporary hospital set up • Temporary port and airport set up to get aid in • People searched for victims trapped in the rubble • 2100 people housed temporarily in refugee camps Long-term responses • Foreign investment in textile industry • Houses rebuilt to be earthquake proof • ‘Cash for work’ programme run by charities Unit 1 A (Paper 1: Tuesday 21 May, pm) • Italian government and EU gave aid • Historic buildings rebuilt and tourists encouraged • Enquiry into building standards and corruption • Warm air rises and cool air sinks around the world in a regular pattern of six convection cells: Hadley, Ferrel, Polar (all x 2). • Sinking air creates high pressure. As it sinks it warms and The challenge of natural hazards Plate Destructive 1. Plates move together. 2. The heavy oceanic crust sinks under the light continental crust (a process called subduction). Friction also creates earthquakes. 3. The oceanic crust melts and its magma rises up through the continental crust. 4. Creating composite volcanoes and island arcs. Example: Japan, Ring of Fire Passive/Conservative 1. Two plates move side- 1. Two plates move together. 2. As both plates are continental, neither sink, but instead they crumple up to form fold mountains. Example: Himalayas, Asia Lazio Region, Central Italy, 6. 2 Mw Global atmospheric circulation Collision by-side. 2. Friction creates earthquakes. Example: California • • Immediate (short-term) • • • Amatrice, Italy, 2016 Island of Hispaniola, Caribbean Sea, 7. 0 Mw Responses to tectonic hazards Plate Mantle Haiti, 2010 Secondary – earthquakes Primary – volcanoes Shield volcano Mid-ocean ridge Plate Primary effects happen immediately. Secondary effects happen as a result of the primary effects and are therefore usually later. Processes at plate margins Constructive Comparing earthquake examples: Haiti (LIC) and Amatrrice, Italy (HIC) Effects of tectonic hazards The distribution (pattern) of tectonic activity • In long lines along plate boundaries. • On the edges of continents. • Especially on the edge of the Pacific Ocean (the Ring of Fire). Reducing the impact of tectonic hazards with the Three Ps (and an M) Monitoring Prediction Volcanoes: detect changes in ground surface height or escaping gas or changes in water levels. Earthquakes: Detect foreshocks with a seismometer. Volcanoes: use data to predict magma chamber filling up just before an eruption. Earthquakes: Use ‘seismic gaps’ to predict when and where quakes will strike. Protection Planning Volcanoes: Use lava walls such as in Hawaii and Etna Earthquakes: Use X and Kbracing, counterweights and base isolation in buildings. Use pipes with rubber joints. Volcanoes and earthquakes: Use seismic risk maps so that hospitals and power stations aren’t put in risky areas. Set aside safe routes for evacuation and emergency vehicles. evaporates, making clear skies. This happens at the hot deserts in the tropics (30°N). • Rising air creates low pressure. As it rises it cools and condenses, making clouds and rain. This happens above the rainforests (0°) and Britain (60°N). Polar cell = On the equator, rainforests grow in the hot, wet conditions Ferrel cell HIGH LOW = dry weather caused by cold air sinking and making high pressure HIGH Hadley cell LOW Hadley cell HIGH Ferrel cell = In the tropics, deserts spread in the hot, dry conditions LOW Polar cell HIGH = wet weather caused by warm air rising and making low pressure
Tropical storms Example of a tropical storm: Typhoon Haiyan, 2013 Tropical storms are huge low-pressure systems, called hurricanes in the Atlantic, cyclones in the Indian and typhoons in the Pac-ific. They form between 5 and 15° N and S, where sea temperatures are 27°C+ Worst affected was Leyte Province (Tacloban city), Philippines Primary effects Secondary effects • • • $14 billion of damage • Water supply polluted with saltwater 6300 killed 130, 000 houses destroyed 5 m high storm surge 90% buildings in Tacloban were destroyed • Mangrove swamps and coral reef habitats were destroyed • • and sewage 4. 2 million homeless Riots and looting Airports wrecked Biodiversity lost Immediate responses Sequence of formation for a tropical storm 1. Evaporation: The sun evaporates water from the warm sea 2. Condensation: Clouds form and grow into giant cumulonimbus 3. Precipitation: The thick cloud gives torrential rain 4. Circulation: The warm air spirals up in a vortex around the eye 5. Rotation: The Coriolis Effect sets the mass of cloud spinning 6. Depressurisation: The sea’s surface rises up as a storm surge 7. Dissipation: It reaches land, loses supply of warm water, weakens Natural and human-made climate change Location Long-term responses • 1, 000 emergency shelters set up • UK’s Disaster Emergency Committee • UN appeal raised $300 million. • Typhoon warning systems has been • 3. 3 m people gave aid • UK aid charities provided shelter, • People are now better educated (DEC) helped improved about how to respond food and medical supplies The three Ps: Prediction, planning and protection Prediction Planning Protection • Satellite surveillance • Weather forecasts • Computer models to • Evacuation routes • National Hurricane • Board up windows and show cone of probability (area likely to be affected – which is hard to predict) Preparedness Week • Networks of cyclists with megaphones in LICs like Bangladesh doors • Put buildings on stilts • Build sea walls against storm surges • Set up cyclone shelters in LICs like Bangladesh Example for extreme weather in the UK: Somerset Levels floods, 2014 Location Somerset, SW England, floodplains of the Rivers Tone and Parrett Tropical storms are measured by their intensity (strength) on the Saffir-Simpson Scale. This goes from Grade 1 (wind speeds 120 - 150 kph) to Grade 5 (over 250 kph). Climate change will affect tropical storms. Warmer oceans will lead to more intense storms, and perhaps more frequent ones. Extreme weather in the UK The UK’s extreme weather events include: • Heavy rain and floods can disrupt travel, ruin property and even cause some deaths (e. g. Cumbria, 2015); • Heavy snowfall can disrupt travel and schools (e. g. March 2018) • Frost and fog can make travel difficult and cause slip injuries; • Strong winds can damage coastal defences and transport links (e. g. rail line to Cornwall and Devon washed away, February 2014) • Heatwaves cause droughts and deaths (e. g. 2000 people in 2003). The UK’s weather is becoming more extreme due to climate change: • More heat energy in the atmosphere so worse storms; • Jet streams (wide, high-level winds) become ‘stuck’ giving us lots of anticyclones (causing droughts) or depressions (causing floods); • Ice sheets melt, dumping cold water in the Atlantic, which weakens the North Atlantic Drift which brings warmth to Britain. Primary effects caused… • 600 homes and many hectares of farmland flooded; • Villages like Muchelney were cut off; and • Bristol-Taunton railway line closed Immediate responses • 16 farms and 1000 cattle evacuated • Residents lived with relatives • Boats were used to get around …Secondary effects • Floodwater polluted with farm chemicals and sewage; • People’s lives affected (commuters couldn’t get to work, nor children to school so their education suffered); • £ 10 m worth of damage Longer-term responses The Earth’s climate has always changed, long before humans were around. But scientists agree that the Earth’s climate is warming at a speed and to a degree that must be down to human activity – the enhanced greenhouse effect. Causes (natural and human) Natural climate change Human-made climate change • Orbital changes: our • Fossil fuels: release CO 2 when orbit changes from being more circular (closer to the sun) to being more elliptical (further away). • Solar output: the sun gives out increased or reduced energy (to do with sunspots). • Volcanic activity: volcanoes warm the climate by releasing CO 2 but cool it by releasing SO 2 which forms a ‘veil’ high up. burnt for power or transport. 50% of emissions. • Agriculture: 20% of greenhouse gases due to methane from cows and rice paddies. Larger populations and increasing demand for meat and rice mean more CO 2 is released. • Deforestation: logging and clearing land for agriculture both increases CO 2 in the atmosphere directly and indirectly because the trees would have absorbed the gas. Effects of climate change (some good, mostly bad) Social x Food shortages in sub-Saharan Africa due to drought. x Droughts in South and South East UK. x More floods due to extreme rainfall ü More holidays in UK due to heatwaves ü Fewer winter deaths due to milder (warmer) weather • Stagnant floodwater re-oxygenated Economic x Lower crop yields (harvest sizes) in LICs due to drought x Fewer sea fish so fishing industry suffers x Less snow so ski industry suffers ü Higher crop yields in HICs (only if irrigation is used). ü Shipping and oil drilling takes place in the Arctic Ocean Environmental x Rainforest dies off due to hotter, drier climate. x Sea levels rise leading to flooding and coastal erosion. x Ice melts leading to extinction of polar bears. x Coral reefs die due to coral bleaching with decline in biodiversity. Evidence for climate change There are two types of evidence for climate change in the past: • Direct evidence: Global temperature records since 1850. • Indirect evidence: Ice and sediment cores, pollen analysis and tree rings. Ice and sediment cores • Ice sheets are made up of compressed snow, one layer per year. Gases trapped in layers of ice can be analysed. Ice cores from Antarctica show changes for 400 000 years. • Remains of organisms found in cores from the ocean floor can by traced back 5 million years. Pollen analysis Pollen is preserved in sediment such as on lake beds. Different species need different temperatures. Tree rings A tree grows one new ring each year. Rings are thick in warm, wet conditions and thin in cold, dry ones. This gives evidence for the last 10 000 years. Temperature records Historical records date back to the 1850 s. Historical records also tell us about harvest and weather reports. before it was pumped into rivers • Rivers dredged (scraped out) • Possible tidal barrage at Bridgewater Managing climate change Mitigation strategies (= reducing carbon dioxide in the atmosphere) • • Carbon capture: taking CO 2 out of the air, liquefying it and pumping it underground. Re-afforestation: planting forests to absorb CO 2 (trees use it for photosynthesis). Alternative energy: replacing fossil fuels with renewables e. g. tidal, solar and wind. International agreements: to reduce CO 2 emissions, e. g. Copenhagen Accord, 2009. Adaptation strategies (= coping with the effects of climate change) • • Changie agriculture in LICs: grow drought-tolerant crops such as millet or GM crops rather than rice Change agriculture in HICs: grow warmth-loving crops such as vines, olives, sunflowers. Reduce water consumption: water meters, grey water flush systems, drip irrigation, artificial glaciers Cope with sea level rise: flood barriers on rivers, sea walls, buildings on stilts, earth embankments.