Changes in the Earth and its Atmosphere - C1

Changes in the Earth and its Atmosphere - C1

1. The Earth has a LAYERED STRUCTURE consisting of the CRUST, the MANTLE and a CORE.

   • CRUST (and upper part of the mantle)
     • cracked into a number of large pieces
       • TECTONIC PLATES
   • surrounded by the ATMOSPHERE

2. The surface of the Earth and its atmosphere have changed since the Earth was formed and are still changing

   • The Earth and its atmosphere provide everything we need
   • human activites = further changes in the atmosphere

3. The atmosphere has been much the same for the last 200 MILLION YEARS

   • provides the conditions needed to live life on Earth
   • the proportions of gases are the same as they were then now
     • 4/5 (80%) NITROGEN
     • 1/5 (20%) OXYGEN
     • other small proportions of various gases
       • e.g. carbon dioxide, water vapour and noble gases

4. CONVECTION CURRENTS

   • in the Earth's mantle - driven by heat released by natural radioactive processes
     • causes the plates to move at relative speeds of a few cm per year
       • movement can be SUDDEN and DISASTROUS
         • EARTHQUAKES
         • VOLCANIC ERUPTIONS
           • occur at the boundaries between the tectonic plates

5. Theories as to how the atmosphere was formed

   • several theories
     • during this period, the Earth's Atmosphere was mainly carbon dioxide and there would've been little or no oxygen gas
       • (like the atmospheres of Mars and Venus today)
       • there may also have been water vapour and some methane and ammonia present
   • during the 1st billion years of Earth's existence there was INTENSE VOLCANIC ACTIVITY
     • this released the gases that formed the early atmosphere and water vapour which condensed to form oceans

6. LIFE ON EARTH

   • Many theories on how life was produced billions of years ago.
     • OCEANS
       • acts as a reservoir for carbon dioxide
       • increased amounts of carbon dioxide absorbed by the oceans has an impact on the marine environment
         • due to an increase in ACIDITY
   • Plants produced the oxygen that is now in the atmosphere
     • methane and ammonia burnt in this ocean producing more water, carbon dioxide and nitrogen
       • most of the carbon from the carbon dioxide in the air gradually became locked up in SEDIMENTARY ROCKS as CARBONATES and FOSSIL FUELS

7. BURNING FOSSIL FUELS

   • nowadays, the release of CO2 by burning fossil fuels increases the level of CO2 in the atmosphere
     • THE GASES IN AIR
       • air - a mixture of gases with different boiling points
         • can be fractionally distilled to provide a source of raw materials used in a variety of industrial processes

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