Transcript No Slide Title

Creation of the Earth
• The earth is 4.6 billion years old.
• After the big bang, the young planet earth formed from
‘accretion’. Accretion is the process of growth from
accumulation. The earth, due to its initial large size, used its
gravitational pull, to attract smaller moons, planetesimals,
asteroids and meteoroids and grew in mass.
• The materials that fell to earth were made up of silicon, iron,
magnesium, water and other volatile elements that turn into
gases at low temperatures.
• As the exterior of the earth cooled and hardened, and once
the solar winds blew away most of the asteroids and
meteoroids, the interior remained molten.
• The heavy material sank down into the core of the earth nickel and iron, while the lighter materials stayed on top on
the earth’s crust - silicon, magnesium and aluminum.
• As the rocks melted and later cooled they gave off gasses
which created an atmosphere. Volcanic eruptions also added
gases to the new atmosphere.
• After cooling the crust had temperatures that ranged from
boiling to freezing. Water vapour began to be converted into
liquid and solid. The liquid fell as rain and filled up the lower
lying areas creating the first oceans.
• The earliest signs of life on earth are in rocks 3.5 to 3.8
billion years old. Early life depended on small amounts of
oxygen. The oceans were the most favourable.
• Early life forms used the process of photosynthesis to create
food from sunlight, carbon dioxide and other minerals and a
by product of this process was oxygen.
1. Meteorite bombardment of the early earth added to its size and the
heat of the impacts kept the earth’s surface in a molten condition. This
process slowed when the sun’s nuclear furnace ignited and the sun’s
newly created solar wind blew away all but the largest of asteroids and
meteoroids.
2. Heating and meteorite impacts, gravitational compression and, most
importantly, radioactive decay melted the interior of the earth. This
melting enabled iron and nickel to sink down to the center to form the
core of the earth. The lighter elements like silicon and magnesium and
aluminum rose to form the mantle and crust. This is known as
‘differentiation’.
3. The melting of the interior also freed many volatile gases such as
carbon and sulphur dioxides, hydrogen, ammonia, methane, and water
vapour from their rocky traps. These gases worked their way to the
surface to form an atmosphere.
4. The arrival of life forms began the transformation of the poisonous
atmosphere of carbon dioxide, ammonia, methane and sulphur dioxide
and water vapour into an oxygen rich one through the process of
photosynthesis (remember - sunlight and carbon dioxide are used to
produce food and oxygen is a by product).
Below is a short movie on the origins of the solar system!