Changes in the Earth and its Atmosphere - C1

The Earth has a LAYERED STRUCTURE consisting of the CRUST, the MANTLE and a CORE.
1. CRUST (and upper part of the mantle)
  1. cracked into a number of large pieces
    1. TECTONIC PLATES
2. surrounded by the ATMOSPHERE
The surface of the Earth and its atmosphere have changed since the Earth was formed and are still changing
1. The Earth and its atmosphere provide everything we need
2. human activites = further changes in the atmosphere
The atmosphere has been much the same for the last 200 MILLION YEARS
1. provides the conditions needed to live life on Earth
2. the proportions of gases are the same as they were then now
  1. 4/5 (80%) NITROGEN
  2. 1/5 (20%) OXYGEN
  3. other small proportions of various gases
    1. e.g. carbon dioxide, water vapour and noble gases
CONVECTION CURRENTS
1. in the Earth's mantle - driven by heat released by natural radioactive processes
  1. causes the plates to move at relative speeds of a few cm per year
    1. movement can be SUDDEN and DISASTROUS
      1. EARTHQUAKES
      2. VOLCANIC ERUPTIONS
        occur at the boundaries between the tectonic plates
Theories as to how the atmosphere was formed
1. several theories
  1. during this period, the Earth's Atmosphere was mainly carbon dioxide and there would've been little or no oxygen gas
    1. (like the atmospheres of Mars and Venus today)
    2. there may also have been water vapour and some methane and ammonia present
2. during the 1st billion years of Earth's existence there was INTENSE VOLCANIC ACTIVITY
  1. this released the gases that formed the early atmosphere and water vapour which condensed to form oceans
LIFE ON EARTH
1. Many theories on how life was produced billions of years ago.
  1. OCEANS
    1. acts as a reservoir for carbon dioxide
    2. increased amounts of carbon dioxide absorbed by the oceans has an impact on the marine environment
      1. due to an increase in ACIDITY
2. Plants produced the oxygen that is now in the atmosphere
  1. methane and ammonia burnt in this ocean producing more water, carbon dioxide and nitrogen
    1. most of the carbon from the carbon dioxide in the air gradually became locked up in SEDIMENTARY ROCKS as CARBONATES and FOSSIL FUELS
BURNING FOSSIL FUELS
1. nowadays, the release of CO2 by burning fossil fuels increases the level of CO2 in the atmosphere
  1. THE GASES IN AIR
    1. air - a mixture of gases with different boiling points
      1. can be fractionally distilled to provide a source of raw materials used in a variety of industrial processes

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Changes in the Earth and its Atmosphere - C1

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