Geography

• Carbon

  An element, symbol C, a non-metal that occurs naturally in different forms
• Diamonds are made of carbon
• The 'lead' in a pencil is not lead at all-it is another form of the element carbon, called graphite
• Living organisms cannot use carbon in the form of an element, they can only use it when it is part of a compound
• Compounds that contain carbon

  • Carbohydrates
  • Proteins
  • Fats
• Photosynthesis


  Plants take carbon dioxide from the air and use it to make carbohydrates
• Carbon dioxide


  A compound that contains carbon atoms combined with oxygen atoms called combusion
• Plants use the carbohydrates to make proteins and fats
• Animals get carbon-containing nutrients by eating plants or other animals
• Decomposers get their carbon when they break down waste products from plants and animals
• The carbon cycle


  1. Photosynthesis

  2. Respiration

  3. Feeding

  4. Combustion

  5. Fossil fuel formation
• Fossil fuels contain carbon that came from the carbohydrates, fats and proteins in dead organisms
• When fossil fuels are burned, the carbon in them combines with oxygen to form carbon dioxide
• Fossil fuels were formed hundreds of millions of years ago from the remains of dead organisms
• Climate: is the long-term pattern of temperatures, wind and rainfalls on Earth.
• Tectonic plates


  The outer layers of the Earth that rest on the more fluid mantle
• Movement of tectonic plates

  1. Heated inner core

  2. Thermal energy transfer through convection currents in mantle

  3. Expansion and rise of heated fluid in mantle

  4. Cooling and sinking of fluid in mantle

  5. Slow movement of tectonic plates
• Mantle


  • Very thick fluid that does not flow easily like water
  • Convection currents move slowly
• Convection currents


  Currents that move across underneath the crust, pulling the tectonic plates along
• Tectonic plate movement is slow, varying between 0.6 and 10 cm per year
• There was once only one large continent that eventually separated into the tectonic plates
• Fossils are the remains of dead animals and plants that have turned to stone over millions of years
• The fossil record provides information about the time before humans were on Earth
• Formation of the Moon


  Formed by splitting away from the Earth, soon after the Earth was formed
• In the early twentieth century, scientists thought that the Moon was formed by splitting away from the Earth
• If the Moon formed by splitting away from the Earth


  The Moon would still be slowly moving away from Earth
• Accurate measurements have shown that the Moon is still moving away from Earth at a rate of about 4 cm each year
• The theory that the Moon formed by splitting away from the Earth could not be completely confirmed
• Collision theory for formation of the Moon


  Also called the giant impact hypothesis, refers to a collision that happened relatively soon after the formation of the Solar System
• Collision theory for formation of the Moon

  1. A newly formed planet, about the same size as Mars, collided with the newly formed Earth

  2. The collision would have caused rocks and dust to break away from both planets

  3. The Earth was formed from the two planets joined together

  4. The Moon was formed when the rocks and dust was pulled together by gravity
• Evidence that supports the collision theory

  • The Moon is less dense than the Earth
  • Samples of rock from the Moon show that its surface was once molten
  • The Moon has a small iron core, similar to the Earth
  • There is evidence outside the Solar System of similar collisions causing rings of rock and dust
  • The collision theory fits with the theory of how the Solar System was formed
  • The composition of rocks on the Earth and the Moon are the same
• Evidence that contradicts the collision theory


  • The surface of the Earth does not appear to ever have been molten
  • Venus has no moon, collisions in the early years of the Solar System would have been common and scientists would have expected Venus to have a moon formed in the same way
  • The composition of the Moon is more similar to Earth than to Theia
• Nebulae


  Clouds of dust and gas in space
• Nebula


  The singular form of nebulae
• Gases found in nebulae

  • Hydrogen
  • Helium
• The particles of gas and dust are very far apart in nebulae
• A nebula the same size as the Earth would have a mass of only a few kilograms
• Most nebulae are very large, some are more than 10000 times bigger than the Solar System
• How some nebulae form


  1. Giant stars reach the end of their life

  2. They then explode, sending dust and gas over a wide area of space
• Nebulae visible from Earth

  • Orion nebula
  • Carina nebula