The ever-changing Earth

• Structure of the earth

  Solid iron inner core

  Molten iron outer core

  Mantle

  Crust
• Theory of plate tectonics

  The earths lithosphere is divided into separate parts known as tectonic plates that move over the mantle at a rate of a couple cm per year in a process known as continental drift.
• What was Alfred Wegener theories

  He thought the continents all used to be joined together in a supercontinent called Pangaea and that the Earths crust and upper mantle was made of sections that drifted apart over millions of year.
• What are the evidence that supports his theory

  Visibly the continents do look as though they once fit together like a jigsaw

  Fossils from the same species were found on continents that are now separate but were once connected in Pangaea.

  The patterns of rock formation is similar on both sides of the Atlantic
• Destructive


  . 2 plates move towards each other

  .Dense of the 2 plates is pushed beneath the other causing it to melt

  . This forms magma which then rises up between the 2 plates creating a volcano or causing an earthquake depending if surface of crust is breached or not

  . The magma then cools forms igneous rock
• Constructive


  .2 plates move away from each other

  . Magma from mantle rises up and forms new rock to fill the gap

  . if pressure is high enough, a volcanic eruption may occur
• Conservative


  . 2 plates slide past each other

  . If the movement is sudden and large enough then there is an earthquake.

  . No volcanoes occur at these boundaries
• How was gases formed in atmosphere

  . There was intense volcanic activity that released gases

  . Started with mainly CO₂ with little or no O₂

  . Volcanoes also produced small proportions of methane and NH3

  . The earth cooled allowing water vapor to condense and form oceans
• Present composition of the atmosphere

  78% nitrogen

  21% oxygen

  small proportions of various gases
• Causes which lead to increase of conc of oxygen

  . Algae and plants release O2 in atmosphere during photosynthesis

  . As plants evolve concentration of oxygen gradually increases, enabling animals to evolve and exist
• How has carbon dioxide conc changed in atmosphere

  . Algae and plants decrease the conc of CO2 in atmosphere by using for photosynthesis

  . Formation of sedimentary rocks and fossil fuels which contain carbon decreases atmospheric CO2

  . Atmospheric CO2 decreases when it decreases when it dissolves in ocean
• How has the conc of ammonia and methane in atmosphere changed

  . As oxygen increases:

  Ammonia reacts with oxygen to form nitrogen and water

  Methane reacts with oxygen to form carbon dioxide and water
• Which 3 processes maintain oxygen and carbon dioxide in atmosphere

  Respiration

  Combustion

  Photosynthesis
• The test used to identify oxygen gas

  Oxygen gas - Glowing splint will relight if placed into a test tube containing oxygen gas
• The tests used to identify carbon dioxide gas

  When bubbled through limewater, carbon dioxide causes it to go cloudy
• Why has conc of CO2 increased in last 100 years

  Deforestation

  Increased burning of fossil fuels

  Population growth
• Major cause of climate change

  Global warming that results in increase carbon dioxide and greenhouse gases level
• Potential effects of global climate change

  . Destruction of animal habitats that may cause extinction of species

  . More extreme weather conditions
• Byproduct of burning fuels other than CO2

  Sulfur dioxide
• How is acid rain formed

  Sulfur dioxide released from burning of fuels dissolves in rainwater forming sulfuric acid (acid rain)
• Effects of acid rain

  . Damages buildings made of limestone

  . Lowers pH of water in lakes
• Measures used to address problems of global warming

  . Reduce fossil fuel usage and use renewable sources instead

  . Encourage recycling and reusing
• Measure used to address acid rain

  Sulfur scrubbing
• Elements found in air

  . Nitrogen

  . Oxygen

  . Argon

  . Neon