Geography

• The Crust


  Varies in thickness (5-10km) beneath the ocean. Made up of several large plates.
• The Mantle


  Widest layer (2900km thick). The heat and pressure means the rock is in a liquid state that is in a state of convection.
• The Inner and Outer Core

  Hottest section (5500oC). Mostly made of iron and nickel and is 4x denser than the crust. Inner section is solid whereas outer layer is liquid.
• Convection Currents


  1. Radioactive decay of some of the elements in the core and mantle generate a lot of heat

  2. When lower parts of the mantle's molten rock (magma) heats up they become less dense and slowly rise

  3. When they reach the solid crust, they can't get through it and so spread away from this point, dragging the crust with them as they go. This tears the crust...creating a crack in the Earth's surface –a plate margin

  4. The moving magma will move away from the point where it reached the crust, cool down, sink and create a circular movement. These movements are called convection currents

  5. Convection currents cause the plates to move (they are dragged by the movement underneath them)
• Destructive Plate Margin


  When the denser (oceanic) plate subducts beneath the other (continental), friction causes it to melt and become molten magma. The magma forces its way up to the surface (through cracks created) to erupt and form a volcano. This margin is also responsible for devastating earthquakes (such as Japan 2011).
• Constructive Plate Margin


  Here two plates are moving apart causing magma to reach the surface through the gap. Volcanoes formed along this crack cause a submarine mountainrange such as those in the Mid Atlantic Ridge. If this mountain range reaches above the ocean surface it will build/construct new land such as Iceland.
• Conservative Plate Margin


  A conservative plate boundaryoccurs where plates slide past each other in opposite directions, or in the same direction but at different speeds. This is responsible for earthquakes such as those happening along the San Andreas Fault, USA and in Haiti!
• Causes of Earthquakes


  Earthquakes are caused when two plates become lockedcausing friction to build up. From this stress, the pressure will eventually be released, triggering the plates to move into a new position. This movement causes energy in the form of seismic waves, to travel from the focus towards the epicentre. As a result, the crust vibrates triggering an earthquake.
• Epicentre


  The point directly above the focus, where the seismic waves reach first.
• Seismic Waves


  Energy waves that travel out from the focus.
• Focus


  The point at which pressure is released.
• Earthquake Prediction Methods


  • Satellite surveying (tracks changes in the earth's surface)
  • Laser reflector (surveys movement across fault lines)
  • Radon gas sensor (radon gas is released when plates move so this finds that)
  • Seismometer-records ground shaking
  • Water table level (water levels fluctuate before an earthquake)
  • Seismic records from the past to predict when the next event will occur
• Earthquake Protection Methods


  • Flexible foundations which isolate the buildings from shockwaves
  • Shatter proof windows
  • Shutters that come down at the first sign of shaking
  • Buildings with shock absorbers (to dampen the force)
  • Using strong but flexible materials (that can bend a little). Steel, wood and alloys can provide strength and flexibility
• Earthquake Planning/Preparation Methods


  • Raising public awareness -they need to know what to do, where to go, what to take. Also, how to set up their home –no heavy items high on shelves; strong table to get under
  • Educating children at school and employees at work
  • 'Duck, cover and hold on' message
  • Drills –there is a Disaster Prevention Day (Sept 1st) in Japan
• Natural Hazard


  A natural event which could cause death, injury or disruption to humans, property and possessions.
• Types of Natural Hazards

  • Geological Hazards (caused by land and tectonic processes...plate movements)
  • Meteorological Hazards (caused by weather and climate...events in the atmosphere)
• Hazard Risk


  The chance of being affected by a natural hazard. A high hazard risk means you are vulnerable.
• Factors affecting Hazard Risk

  • Proximity – how close you are to a volcano or plate margin…closer=more hazard risk
  • Wealth of your country – HIC's will have strategies in place to cope…LIC's will not
  • Education/awareness – you may know what to do, what to take and where to go
  • Design of buildings - are they earthquake proof; do they have steel supports; are they densely pack together
• Plate Tectonic Theory


  The theory that the hot core drives convection currents inside the Earth to crack the crust and create plate margins (the cracks). The pieces either side of the plate margins are called plates.
• Sometimes the plates move together, sometimes they move apart and sometimes they 'slide' past one another – although there is no smooth movement!
• Scientists came up with idea of plate tectonics after looking at the 'fit' of the continents coastlines (Africa and South America) and the ridges in the ocean floor (Mid-Atlantic Ridge) among other things.
• Reasons to live in a hazardous area

  • Fertile land near a volcano (nutrients in the ash, lava)
  • Tourism revenues (volcano)
  • Geothermal energy all your energy needs met
• Global Atmospheric Circulation


  At the equator, the sun's rays are most concentrated. This means it is hotter. This one fact causes global atmospheric circulation at different latitudes. High pressure = dry (due to the sinking air), Low pressure = wet (due to the rising air). Winds blow from high pressure to low pressure. They curve/get deflected because of the Coriolis Effect (caused by air moving over the spinning Earth)
• Tropical Revolving Storms


  Occur in low latitudes between 5 and 30 degrees north and south of equator. NOT at the equator...there is not enough deflection here to spin the storm. Ocean temperature needs to be above 27oC. Happens between summer and autumn (when the water is at its warmest...it takes a while for water to warm). Water needs to be 50m+ deep. Latent heat of condensationsupplies heat to the storm (when condensation occurs) causing air to warm, rise and condense further.
• Primary Effects of Hurricane Katrina

  • 1800 killed
  • 300 000 homes destroyed
  • 80% of New Orleans flooded
  • 3 million people without electricity
  • 500 oil rigs out of action in the Gulf of Mexico
  • 560km2 of land 'lost' - now flooded
• Secondary Effects of Hurricane Katrina

  • 20% less gas produced – spike in price
  • 230 000 jobs lost from damaged businesses
  • Water supply polluted
  • Hundreds of thousands homeless
  • Total cost of damage $150 billion
  • Looting
  • Thousands left the city (35 000 to Houston)
  • Racial tensions due to the Black people 'left'
• Immediate Responses to Hurricane Katrina

  • 70-80% of New Orleans evacuated before hurricane reached land
  • State of emergency declared in Louisiana and Mississippi
  • Emergency shelters set up - many evacuated to the Louisiana Superdome
  • 50 000 people rescued (bats and helicopters)
  • Charities provided hot meals and aid
• Long-term Responses to Hurricane Katrina

  • Government provided $16 billion to rebuild
  • Some houses rebuilt on stilts; others built as 'dome homes'
  • Some areas zoned 'no build' areas
  • Repaired flood defence costing $14.5 billion (mainly levees)
  • Re-establishing of mangrove areas along the Gulf of Mexico coast (they can act as a buffer)
• Sequence of a Tropical Storm Formation

  1. Air is heated above warm tropical oceans

  2. Air rises under low pressure conditions

  3. Strong winds form as rising air draws in more air and moisture causing torrential rain

  4. Air spins due to Coriolis Effect around a calm eye of the storm

  5. Cold air sinks in the eye so it is clear and dry

  6. Heat is given off as it cools (latent heat of condensation) powering the storm

  7. On meeting land, it loses source of heat and moisture so loses power

  8. Symmetrical pattern to storm
• Extreme Weather in the UK

  • Rain – can cause flooding damaging homes and business
  • Snow & Ice – causes injuries and disruption to schools and business. Destroys farm crops
  • Hail – causes damage to property and crops
  • Drought – limited water supply . Can damage crops
  • Wind – damage to property and damage to trees potentially leading to injury
  • Thunderstorms – lightning can cause fires or even death
  • Heat waves – causes breathing difficulties and can disrupt travel
• UK weather is getting more extreme due to climate change. Temperatures are more extreme (summer of 2022!...the 4th hottest recorded (2018, 2006, 2003 were hotter) and rain is more frequent and intense leading to more flooding events. The decade 2010-19 saw average temperatures that were 0.9oC higher than the 1961-1990 long term average.

  
• Some experts have noticed that the jet stream is more fixed in its position high over the UK. This means that locations get the same type of weather for longer...leading to floods (extended wet weather) or drought (extended dry weather).
• Flood Management Strategies in Cockermouth

  • A self-raising floodwall (first of its type in the world) in front of riverside homes
  • Roads were raised in flood prone areas in the town
  • Flood gates (barriers) and flood-proof windows have been introduced
  • Farmers upstream have left boggy fields undrained and long grass in fields
• Climate change will mean warmer oceans, leading to more frequent and intense storms – climate change causing extreme weather! In tropical locations but also in the UK!
• Causes of Climate Change

  • Natural (Orbital changes, Solar Output, Volcanic activity)
  • Human (Greenhouse gas emissions, Deforestation, Agriculture)
• Climate change is natural. However, the rate of change since the 1970s is unprecedented. Humans are largely responsible – despite what some politicians say
• Causes of climate change

  • Natural
  • Human
• Natural causes


  • Orbital changes - shape of Earth's orbit around sun changes over 100,000 years, affecting climate
  • Solar output - sunspots increase every 11 years, heating Earth by 0.1°C
  • Volcanic activity - aerosols reflect sunlight, reducing temperatures, but also release CO2 contributing to warming
• Human causes


  • Fossil fuels - release CO2, accounting for 80% of human-caused greenhouse gases
  • Deforestation - reduces carbon storage in trees, releasing CO2
  • Agriculture - clearing forests for grazing and rice production releases methane
  • Growing populations and living standards increase demand for energy, travel, meat and rice, increasing human contributions
• Evidence for climate change

  • Ice and sediment cores
  • Tree rings
  • Pollen analysis
  • Historical records and photos