A Discussion on Various Theories of Plate Tectonics

Our world is an amazing thing. Scientists have worked to try to understand as much as they can about our earth including how it changes. Plate tectonics is a relatively recent idea explaining how the surface of our earth changes. Our earth is constantly changing, the early theories of plate tectonics having grown through the years; from Alfred Wegener’s theory of Continental Drift to Harry Hess’ theory of Seafloor Spreading scientist have expanded upon the knowledge of the constantly changing earth.

Our earth’s crust and mantle are constantly in motion. Different pieces, or plates, move at different times. If one observes the Himalayan Mountains, one can easily see how the surface of the earth changes. The mountain grow a few centimeters in height every year as the Eurasian and Indian Plates hit each other. Magma nearest to the center of the earth is heated up. As it goes nearer to the surface it decreases in heat and falls falls back down; thus creating a convection cell. As the circle rotates it pushes the earth’s surface. This is the cause of plate tectonics.

The earliest idea of plate tectonics came from scientist Alfred Wegener. Alfred Wegener came up with the idea of Pangea, or super earth. The idea of Pangea is the concept that all of the landmasses on the earth were once a super continent and there was one giant ocean. Wegener believed that throughout time somehow the continents spread apart. His concept wasn’t widely accepted at the time even though he had three major pieces of evidence. The first of which is that the continents seemed to fit together like a puzzle. As pointed out in class this is likely his most important piece of evidence. His second piece of evidence is that the mountain ranges and deserts match up where the continents fit together matched. His third piece of evidence is that similar fossils were found in both africa and south america; this would imply that at some point the two continents were next to each other. His idea was not popular but was eventually proven as was Harry Hess’ idea.

Harry Hess’ came up with the idea of seafloor spreading. We studied the largest underwater mountain range. The Mid-Atlantic Range, he discovered, is actually a large chain of underwater volcanoes constantly erupting. When the magma pours out it pushes the current seafloor and adds to it. He discovered that the seafloor was being added to. The rocks within the seafloor record the pull on them by the magnetic poles. The earth switches its magnetic pull every thousand years so rocks pulled by the north or south pole are marked by either white or black respectively. When he noticed the lines, zebra stripes, he concluded that the sea floor is newer in some parts that others.

These two theories became the modern concept of plate tectonics. Plate tectonics is still a relatively new field of study. Scientists are still trying to unlock the mysteries of plate tectonics. We know that the earth moves constantly and that mantle convection is the cause. One should appreciate Hess and Wegener for being pioneers in this new field of plate tectonics.