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.