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 HOW
WAS EARTH FORMED?
Planet Earth was formed 4.6
billion years ago from the same nebula cloud of gas and
dust that the Sun and the other planets were formed (similar to the one
pictured to the left). However, Earth then was very different
from Earth now, and it would have been impossible for life to
exist on it. In fact, it is only quite recently in the Earth's
4,600,000,000 year long life that life, resembling modern-day
life, has been possible, first with the dinosaurs over
200,000,000 years ago and now with humans and other animals. The
Earth is still being formed now. It still has a molten centre
which causes volcanoes to ocassionally erupt, and plates on the
surface are constantly "swimming" meaning that they
collide with other plates and cause earthquakes. On this page, we
will look at how Earth may have settled to become like the planet it is
now.
 4,000,000,000
YEARS AGO
This
is an artist's impression of what Earth looked like 4 billion
years ago. The planet has no oxygen in its atmosphere and no
ozone layer, so poisonous ultraviolet rays from the Sun
hit the surface directly.
The molten centre of the planet is still extremely hot, and
volcanoes erupt constantly, forming the mountains and landscapes
of the planet. Water droplets, contained in the planet's
atmosphere, cannot settle as liquid or ice because the surface is
so hot.
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 1,000,000,000 YEARS AGO
The
planet has cooled and volcanic eruptions are less common. Water
is now allowed to settle, and forms oceans. Green algae forms in
the water, which photosynthesises and produces oxygen which is
put into the air. The oxygen forms a layer of ozone which
protects the Earth from poisonous ultraviolet rays from the Sun. Land drifts apart to
begin forming continents.
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 400,000,000 YEARS AGO
Life
begins developing in the form of trees and plants. These produce
more oxygen. Earth has a cooler temperature, with changeable
weather. This weather (rain, snow, wind, frost) causes the tops
of the ancient volcanoes to wear away, creating lower ground.
Dinosaurs eventually develop, ruling the planet. Flowers are
later formed, along with insects.
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 65,000,000 YEARS AGO
Life
was wiped off the face of the planet! It is believed that a huge meteorite hit the Earth's surface,
causing clouds of dust which suffocated the dinosaurs and other
creatures on the planet. Conditions on the planet were
suffocating as poisonous chemicals were unable to leave the
planet's atmosphere, and life-giving energy from the Sun could not enter. After
settling again, the Earth was suitable for life, an the ancestors
of human beings developed.
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TODAY
Earth
is still developing. Volcanoes still erupt, the earth still
shakes, weather still forms landscapes. Creatures evolve. Some
die out, some develop. The creatures that die out do so because
they are not suitable for the planet's current conditions.
Creatures that survive and flourish do so because they are more
adapted to the new conditions. Nobody knows what the future
holds. The air is becoming more polluted, and the temperature on
the planet is gradually increasing. Earth's protective ozone is
wearing away. Earth remains a target for meteors, comets and asteroids travelling through space.
There is always a chance that one may hit the planet eventually
and destroy life as we know it. Perhaps, the planet will be
reborn again as the dust settles.
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