Changes in the Earth & its Atmosphere

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The Earth's Structure

The Earth has layers to it's structure:(http://a.files.bbci.co.uk/bam/live/content/zyp3b9q/large)

The crust & upper part of the mantle are cracked into large pieces called techtonic plates. The plates move a few cm each year ( because of convection currents) , causing earthquakes &volcanoes whenthey slide past each other  (http://www.moorlandschool.co.uk/earth/earth_science/plate_colour_diagram2.gif)

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Theories Of The Earth

The Shrinking Earth Theory:

  • The Earth started as a lump of molten rock
  • As it cooled further, the inner part contracted & the skin wrinked, forming valleys and mountains

The Expanding Earth Theory:

  • The Earth started off a lot smaller
  • It has expanded over time
  • The crust cracked & the continents moved apart

Continental Drift:

  • Millions of years ago, the continents were one 'supercontinent', called Pangea
  • Over time, Pangea split up & different bits drifted around the globe
  • The continets are still moving now
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The Early Atmosphere

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The Earth's Atmosphere

The Earth's atmosphere contains:

  • Nitrogen, 78 %
  • Oxygen, 21 %
  • Argon, 0.9 %
  • Carbon dioxide, < 0.1 %
  • Water vapour, constantly changes

The main gases in air can be seperated by fractional distillation:

  • Air is filtered to remove dust
  • Water is removed
  • Carbon dioxide is then removed by absorption
  • The remaining gases are compressed & cooled to -200 degrees
  • Just like oil fractions, the column is hotter at the bottom than top

Nitrogen & oxygen are used to freeze food & increase shelf life, reduce chances of explosion in oil tankers, etc.

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