Physics 3 earth science

• The crust


  • 50 km thick
  • Average temperature of 22 degrees Celsius
  • Made of rock
  • Split into tectonic plates
  • Convection currents in the mantle cause the tectonic plates to move, split up and rub together
• The mantle


  • 2900 km thick
  • 1400 - 3000 degrees Celsius
  • Intense heat from the core heats up the mantle which is liquid
  • Causes convection currents
  • Made of magma
• The outer core


  • 2200 km thick
  • 4400 degrees Celsius
  • Made of liquid iron
• The inner core


  • 1200 km
  • 5430 degrees Celsius
  • Pressure from the outer layer causes immense pressure to form at the Earth's centre
• Continental drift


  1. The Earth's crust and upper part of the mantle are broken into large pieces called tectonic plates

  2. These are constantly moving at a few centimetres each year

  3. Over millions of years the movement allows whole continents to shift thousands of kilometres apart
• Continents move 1.5 - 2.0 cm a year
• Scientists predict that as the continents are continuously drifting together before breaking apart in a never ending cycle that will one day lead to another Pangea
• Formation of Pangea


  1. The earth used to have just one huge bit of land mass which was a supercontinent called Pangea

  2. Over time Pangea has split up into tectonic plates due to the convection currents in the magma in the mantle

  3. The mantle is a liquid so due to the high temperature in the earth's core - it heats up the mantle and the convection currents force the tectonic plates to split up and collide with one another
• Formation of the Earth's atmosphere

  1. The early earth was just a ball of molten rock with its atmosphere consisting of hydrogen and helium

  2. As the ball cooled down a crust formed and volcanoes would burst forth from the molten rocks below

  3. These volcanoes erupted and gave out gases such as carbon dioxide (CO2), ammonia (NHs), methane (CH4) and steam (H20)

  4. As the Earth cooled down even more, the steam condensed and fell as rain, filling up hollows in the Earth's crust and forming the oceans

  5. The first living things appeared in the oceans

  6. At that time there was no ozone layer

  7. The UV light from the sun was too intense for anything to live on land

  8. Some scientists believe that the first living creatures evolved near underwater volcanoes where all the nutrients and raw materials were present for living things to sustain themselves

  9. The first organisms evolved into simple plants, like algae

  10. These algae used up carbon dioxide in photosynthesis and made the first molecules of oxygen (2) gas

  11. This gas did not build up into its present level straight away because at first it probably reacted with metals and other elements to form oxides

  12. After some time, the oxygen started to build up in the atmosphere

  13. Some reacted to form the ozone layer, which shielded the Earth from harmful UV light

  14. At this point, it was possible for organisms to leave the water and start to live on land

  15. Eventually the percentage of oxygen and nitrogen in the air reached their present value of 21% and 78% respectively

  16. The respiration carried out by animals produces carbon dioxide whilst photosynthesis uses the carbon dioxide, locking it up in sugars and producing oxygen gas. Thus the gases remain in balance
• Oxygen appeared in the atmosphere because the Earth's first organisms like algae used up the carbon dioxide for photosynthesis and made the first molecules of oxygen
• Oxygen formed the upper layer in the atmosphere called the ozone layer
• The ozone layer allowed animals and plants to respire and photosynthesise
• There has been an increase in carbon dioxide due to global warming which is caused by too many greenhouse emissions meaning there is too much carbon dioxide in the atmosphere
• Igneous rocks


  • Formed from liquid rock from the mantle
  • This liquid rock is continually rising towards the crust, and when it cools enough, it will turn into a solid, forming new rock
  • This can happen in places where the plates are moving apart
  • Examples: Basalt, pumice, Granite, Obsidian
• extrusive igneous rocks

  • Formed from the lava which has been ejected out of the earth through volcanoes
  • Extrusive rocks form on the outside of the volcano and due to lava cooling quickly the rocks form quicker allowing less time for crystals to form so the crystals in extrusive igneous rocks are smaller
• intrusive igneous rocks

  • Formed from the magma and are formed inside the volcano due to magma cooling slower so the rocks cool slower
  • This causes the crystals to cool slower, so the crystals have more time to cool and are bigger
• Magma


  Molten rock that is underground
• Lava


  Molten rock that breaks through the earth's surface
• Formation of sedimentary rocks


  1. Weathering of existing rock is the first stage

  2. Smaller rock pieces (from weathering) are moved from one place to another by wind, water and glaciers

  3. Transported pieces of weathered rock settle to the bottom of the river or sea

  4. Sedimentation: Sediment settles on the river or sea bed to form layers

  5. Compaction: The weight from the top layers push down on the bottom layers

  6. Cementation: Water is squeezed out from between the rock and the rocks begin to stick together
• Metamorphic rocks


  • Made underneath the earth from sedimentary and igneous rocks that are deep underground
  • The further down they are the hotter it gets
  • They are also squashed by the weight of sediment above them
  • These existing rocks (sedimentary and/or igneous) morph under the heat and pressure to become new metamorphic rocks
• The rock cycle


  1. Igneous rocks are formed and are then weathering, erosion, deposition and then sedimentation, compaction and cementation takes place causing sedimentary rock to form

  2. Then pressure and heat cause metamorphic rocks to form

  3. Then the metamorphic rock heats up and turns into magma and the process of forming igneous rock starts again kicking off the rock cycle
• Sedimentary rocks


  Formed from layers of sediment: igneous rock: weathering, erosion deposited and compacted/squashed over many years, then cementation/becoming glued together
• Metamorphic rocks


  Formed underground from the action of heat and pressure on sedimentary and igneous rocks
• Igneous rocks


  Formed from liquid rocks - either magma cooling slowly (intrusive) or lava cooling quickly (extrusive)
• The greenhouse layer


  • Made up mainly of CO2 and methane
  • The greenhouse effect has been essential for the development of life on Earth
  • Without the greenhouse effect, the Earth would be much colder – around -18°C
  • The problem is that the greenhouse effect is being increased because the layer of gases is getting thicker
  • Greenhouse gases like carbon dioxide and methane are added to the atmosphere
• The greenhouse effect


  1. The Sun's infrared rays pass through the greenhouse gases and warm up the surface of the Earth

  2. The Sun's heat is reflected from the surface of the Earth

  3. The greenhouse gases stop the reflected heat from passing back out into space

  4. The atmosphere warms up. This is called global warming
• The greenhouse gases are carbon dioxide, oxygen, and methane
• The additional carbon dioxide being added to the atmosphere results in the greenhouse layer being thicker, and so more of the heat is being absorbed and re-emitted, causing the Earth's average temperature to increase
• label the earth structure

  A) the crust

  B) mantel

  C) outercore

  D) inner core

  
• label the rock cycle

  A) sedimentary rock

  B) metamorphic rock

  C) igneous rock

  D) weathering

  E) heating and cooling

  F) pressure and heat

  G) pressure and heat