A TIMELINE FOR
THE PLANET click for Home Page
The newly-formed Earth was largely molten, and it has
been gradually cooling down ever since.
After ‘only’ 500 million years, our planet had cooled
enough for there to be liquid water; and land as we know it (more) –
with rivers and streams. But
just underneath the surface, the ‘mantle’ was still much hotter than it is
today. In consequence the Plate Tectonic
processes were much more active (more). There may have been much the same amount of
land as today. However it will have comprised masses of small islands
rather than huge continents. Conditions
were too turbulent for anything but bacteria to survive. In fact some scientists claim that even
bacteria wouldn’t have stood a chance.
After 2 thousand million years (2½ kMy
ago), there were definite signs of our planet slowing down, hence the change
from the ‘Archaean’ Aeon to the ‘Proterozoic’.
But it was still not ready for anything much larger than an amoeba.
Not for another 2 thousand million years did ‘large
scale’ life such as trilobites and the Burgess Shale fauna appear.
Today the planet is very old indeed. And the plate tectonic processes are getting
seriously sluggish. However they will
not stop completely for a long time yet.
This is just as well because it is Plate Tectonics that is continually
piling up the land as fast as erosion wears it away. When the Plate Tectonics stops the land will
all disappear beneath the sea.
© C B Pease, Sept 07