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.