earth
- Created by: Ellie cooper
- Created on: 02-12-12 19:33
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- Our changing planet
- Structure of the Earth
- The Earth is made of layers called the core mantel and crust with the atmosphere around the outside
- The Earth`s limited resources come from its crust, the ocenas and the atmosphere
- The restless Earth
- The Earth`s crust and upper mantle is cracked into tectoic plates which are constantly moving
- The tectonic plates move because of convection currents in the mantle that are caused by radioactive decay
- Earthquakes and volcanoes happen where tectonic plates meet, but it is difficult to predict accurately when and where the earthquakes will happen
- Wegener`s theory of continental drift was not accepted for many years
- The Earth`s atmosphere in the past
- The Earth`s early atmosphere was formed by volcanic activity
- It probably consisted mainly of carbon dioxide. There may also have been water vapour together with traces of methane and ammonia
- As plants spread over the Earth, levels of oxygen in the atmosphere increased
- Life on Earth
- There are many theories about how life began on Earth
- One theory states that the compounds needed came from reactions involvng hydrocrabons and ammonia and lighting providing energy
- All the theories about how life started on Earth are unproven and so we cannot be sure how life began
- Gases in the atmosphere
- Most of the carbon dioxide in the early atmosphere became locked up in sedimentary rocks
- About four-fifths(almost 80%) of the atmosphere is nitrogen and about one-fifth(just over 20%) is oxygen
- The main gases in the air can be seperated by fractional distillation. These gases are used in industry as raw materials
- Carbon dioxide in the atmosphere
- Carbon moves into and out due to plants, animals, the oceans and the rocks
- The amount of carbon dioxide in the Earth`s atmosphere has risen in the recent past largely due to the amount of fossil fuels we now burn
- Structure of the Earth
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