THE UNIQUE EARTH AND GEOMORPHOLOGY
( Page 1) |
|
| “In the beginning
God created the heavens and the earth” Gen: 1, 1. |
| About ten billion years after creation, that is, five
billion years before the present, one of the second-generation stars
ended up its life after having spent all its nuclear fuel in creating
heavy elements. During this explosive event this dying star turned
itself into what is called a supernova. This explosion sent the heavier
elements in the star hurtling far out into space while the lighter
ones, mostly hydrogen and small quantities of helium and lithium,
remained at the centre of this dispersed mass of matter. The space
around this also contained plenty of gases and dust just as in other
spaces between stars. |
| Whether it was evolution by chance or creation by design,
the lighter matter in the central region of this swirling disc gathered
into one huge ball of fire. The tremendous force of gravity caused
the temperature to soar and nuclear fusion again took over. A new,
third- generation star was born. We call it the sun and it remains
in one corner of our galaxy, the milky way, which consists of a hundred
billion other stars as well as supernovae, black holes, neutron stars,
white dwarfs and red giants. |
| Once it was thought that the planets were created simultaneously
with the sun. But the opinion of the scientific community of today
is that the planets formed only a couple of million years after the
birth of the sun. During this period, the matter that today forms
the planets and asteroids was a disc-shaped cloud of dust and gas
called a nebula. This nebula progressed round our infant sun like
a giant record player in slow motion, until something happened - something
that looked natural in the past but seems inexplicable today. The
matter of the cloud gradually condensed into bigger and bigger lumps
until the asteroids and planets were formed, shall we say, created.
Creation of the earth was not something that happened with the birth
of the sun nor something that is quite normal in the process of cosmic
evolution. The sun could have had its entire life with just a nebula
of dust and gases around it for all that we know. Many stars have
such nebulae around them throughout their lifespan. What happened
a few million years after the creation of the sun was a separate act
of creation, the creation of the planets, the creation of the earth,
a home for us. |
| The Icy Planet |
| The earth started probably as a ball of molten rock
of uniform density. As it cooled the gravity brought the heavier metals
to the centre, with concentric layers of varying density and composition.
It consisted of a central core of solid nickel-iron surrounded by
the outer core of molten nickel-iron. Over this were the semi-solid
mantle, partially molten asthenosphere, and the solid crust or lithosphere.
The lithosphere consisted of the silicates and oxides of metals as
well as quartz, the oxide of silicon. The lightest oxide, water, formed
the outermost layer called the hydrosphere and above this was the
atmosphere of gases, mostly nitrogen and carbon dioxide. The water
on the surface of the earth was in the frozen state because, the sun
in those days, was not as hot as it is today. This state of affairs
did not last long. The heat produced by the constant bombardment of
meteorites, the heat of the sun as well as the heat emitted from the
radioactive elements of the earth from inside it thawed most of the
ice and at least the tropics were covered with water in the liquid
form. Still there was no dry land. |
|
