the ever changing earth - Alfred Wegener

• Inner Core


  The hottest part of the Earth, temperatures up to 3,500°C, made primarily of iron with some nickel
• Outer Core


  Liquid layer that is also made of iron and nearly as hot as the inner core
• Mantle


  The thickest part of the Earth, contains semi-molten rock, more solid towards the outer edge and more molten towards the core
• Crust


  The thinnest part of the Earth, its thickness varies but can be up to 70 km
• Plate Tectonics


  • The Earth's outer layer, called the lithosphere (crust and rigid part of the mantle), is broken into 7-8 major and many minor plates
  • These plates "float" on the mantle and move at speeds of a few cm per year
  • Plates can move suddenly, causing earthquakes
• Alfred Wegener


  Hypothesised in 1912 that Africa and South America had previously been one continent which had then split, based on evidence such as matching rock layers, similar fossils, and the coastlines fitting together
• Wegener's theory did not include an explanation for how the continents move, and was initially dismissed by scientists
• The idea of convection currents below the crust was researched and accepted as the true mechanism for plate tectonics in the 1930s and 1960s
• Destructive Plate Boundary


  • One plate is pushed down into the mantle and melts to form magma, creating explosive volcanoes
  • The oceanic crust sinks below the continental crust, a process called subduction
  • Fold mountains often form along this boundary
• Constructive Plate Boundary


  • Plates move apart, allowing molten rock (magma) from below the surface to be released and cool to form new igneous rock
  • This can cause volcanic explosions, and the formation of new islands like Iceland
• Conservative Plate Boundary


  • Plates slide past each other, generating powerful earthquakes but no volcanoes as no rock melting occurs
  • The San Andreas Fault in California is an example
• Creation of the Atmosphere

  1. Volcanoes released carbon dioxide, ammonia and water vapour, creating the first atmosphere

  2. As the Earth cooled, the water vapour condensed to form oceans

  3. Photosynthesising bacteria formed in the oceans, consuming CO2 and releasing oxygen

  4. Oxygen reacted with ammonia to form nitrogen, the most abundant gas in the atmosphere

  5. Oxygen combined to form ozone, creating a protective layer
• Current Atmospheric Composition


  Nitrogen 78%, Oxygen 21%, Argon (plus other noble gases) 0.9%, Carbon dioxide 0.04%
• Photosynthesis


  CO2 in, O2 out
• Respiration and Combustion


  O2 in, CO2 out
• In the past hundred years, humans have increased combustion by burning fossil fuels and decreased photosynthesis due to deforestation
• Sulfur dioxide forms from burning impurities within fossil fuels, and reacts with water to form sulfuric acid (acid rain)
• Acid Rain


  • Clean rain has a pH of 5.5, while acid rain has a pH in the range of 2-4
  • Acid rain lowers the pH of lakes, rivers and ponds, damaging aquatic life and vegetation
  • It also increases the rate of corrosion of metal structures
• Sulfur Scrubbing


  Exhaust flue gases of fossil fuel plants are filtered to remove sulfur dioxide
• Carbon dioxide acts like a "cushion" around the globe, preventing heat from escaping, leading to global warming
• Global warming can cause changing weather patterns, flooding, melting of ice caps and glaciers, and rising sea levels
• Carbon capture involves storing the CO2 produced by burning fossil fuels under the sea or underground, but there are no simple solutions to the environmental problems of burning fossil fuels
• The best way to reduce CO2 emissions is to become 'responsible consumers' of energy and utilise alternative energy sources
• Gas Tests


  • Oxygen - glowing splint relights
  • Carbon dioxide - bubbles through limewater, turns cloudy
  • Hydrogen - lit splint makes a "squeaky pop" and the gas burns