Earth As Living Machine
We live in an extraordinary era of
exploration. We are now able to reach far out
into space and deep down into
the ocean. We have the advantage with technology
such as computers and
satellites. We can now simply understand the dynamic
forces that shape our
Earth. Our Earth is constantly destructing and recreating.
It balances
through a continuous rebirth cycle. The Earth’s dynamic shape can
be summed
up very simply-Transfer Of Energy. This "Big Idea" helps to
explain many
things such as plate tectonics, ocean floor spreading, continental
drift,
volcanoes, earthquakes, just about everything that happens naturally
on
earth. Plate Tectonics links together Alfred Wegener’s theory of
continental
drift and Harry Hess’s theory of ocean floor spreading. Alfred
Wegener was a
German meteorologist living in the first half of this
century. He thought that
long, long ago at one time all of the continents had
been joined together as one
gigantic land mass he called Pangaea. Finally
after a long period of time the
huge land mass had broken apart and slowly
became what it is today and was
believed to be still changing. Many
scientists did not accept Wegener’s
theory, but he kept on collecting
evidence to support it. Finally, fossils of
the same organism on many
different continents were found. This helped to
support his idea even more
then fitting the continents together like a puzzle.
Glossopteris fossils,
which are found in rocks, were found in South America,
Australia, India,
and Antarctica. These organisms were too large to be carried
continent to
continent by wind and were not tough enough to survive a trip
across the
ocean. This made scientist confused. One of the clearest sets of
evidence is
found in the rocks of Africa and South America. The rock formations
in Africa
lined up with matching ones in South America. Several years after
Wegener
had died, the theory of Continental Drift was finally accepted. It was
very
hard for many of the scientists to accept that the continents would have
to
plow through hard, solid ocean floor. During the 1950’s and 1960’s
new
equipment and methods enabled scientists to make better observations of
the
ocean floor. With special mapping techniques the scientists discovered a
very
large rift valley in the center of the ocean. These chains of
underwater
mountains are called the midocean ridges. This 80,000 kilometer
long mountain
chain is the largest in the world! Ocean floor spreading is
when lava erupts
from the rift valley that runs the length of the ridge. As
the ocean floor moves
away on both side of the ridge lava wells up and
hardens. The hardened lava
forms a new ocean floor. As a piece of the ocean
floor moves it takes the
continent with it. As the ocean floor spreads, the
older rocks move further away
from the ridge. New deep-sea drilling machines
also provide evidence to support
this idea. Scientists have now also
discovered that the hardened lava is leaving
magnetic stripes. Some minerals
have magnetic properties and in molten rock the
magnetic mineral particles
line up in the direction of the Earth’s magnetic
poles. This phenomenon has
cause the poles to reverse themselves nine times!
Because of ocean floor
spreading it might make you think that the Earth is
getting bigger. Well,
that wrong, here’s why. The oldest rock on land is about
400 billion
years old, while the oldest rock on the ocean floor is only about
200
million years old. The ocean floor is being destroyed as fast as it is
being
created by ocean floor spreading. The compelling evidence for
continental drift
and ocean floor spreading caused many of the old theories
about the Earth to be
forgotten. Soon a new theory about the evolution of the
Earth came about and it
was named Plate Tectonics. This theory states that
there are many, many plates,
or irregularly shapes slabs that fit together,
that float on top the mantle.
These plate are carried along and bring
along the continent, country or island
that sit atop it. This theory help to
explain the formation, movement, collision
and destruction of the Earth’s
crust. This links continental drift and ocean
floor spreading and explains
how the earth has evolved over time. There are
seven major plates of the
Earth, some are very large and some are very small.
These plates seem to
be moving in all different directions and speeds. The
plates will have one of
the three types of plate boundaries. Either the
divergent, convergent, or
strike-slip. The divergent boundary occurs at a
midocean ridge, in which they
move apart from one another. When the plates come
together at a trench the
boundary is called convergent. Boundaries formed by a
lateral fault are the
strike-slip boundaries. These two plates will slip and
grind past each other.
One of the most famous strike-slip boundaries is the San
Andreas Fault in
California. On the west, the Pacific plate is slowly grinding
northwest while
the plate on the east, the North American plate, is sliding
west. By the
1960’s it became obvious that the Earth was far more dynamic then
ever
imagined. What could "Transfer of Energy", or the heating and
cooling of the
Earth, have anything to do with plate tectonics? In plate
tectonics as you
know there are many lithosphereic plates. Under these plates
there is very
hot magma. This magma is constantly heating and cooling. This
heating and
cooling cycle is forming a circular motion or a convection current.
This
convection current carries along the plate that floats on top of it
causing
the continents to move. It took about 400 billion years or so to
create what we
come to know now. Our Earth has many dynamic forces that
destroy it and there is
those that help to create it. Our Earth is constantly
changing and it never
rests. Some people might think of the Earth as a dead
thing that we just walk
upon but it’s far more then that. The Earth is our
Living Machine.