A Discussion on Various Theories of Plate Tectonics

Introduction

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, scientists have expanded upon the knowledge of the constantly changing earth.

A Discussion on Various Theories of Plate Tectonics

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 mountains grow a few centimeters in height every year as the Eurasian and Indian Plates collide. Magma nearest to the center of the earth is heated up. As it rises nearer to the surface, it decreases in heat and falls back down, thus creating a convection cell. This cyclical movement is what drives the mechanism of plate tectonics.

Alfred Wegener and the Theory of Continental Drift

The earliest idea of plate tectonics came from scientist Alfred Wegener. Wegener proposed 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 supercontinent and there was one giant ocean. Wegener believed that over time, the continents somehow 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. 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 adjacent. Although his idea was initially unpopular, it was eventually proven as was Harry Hess’ idea.

Harry Hess and the Theory of Seafloor Spreading

Harry Hess proposed the idea of seafloor spreading. We studied the largest underwater mountain range. The Mid-Atlantic Ridge, 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 few 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 than others. This revelation provided crucial insights into the dynamic processes shaping our planet's surface.

Conclusion

These two theories became the modern concept of plate tectonics. Plate tectonics is still a relatively new field of study, and scientists are still trying to unlock its mysteries. 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. Their groundbreaking work laid the foundation for future research, enabling scientists to better understand the complex interactions between the earth's surface and its inner layers.

References

Wegener, A. (1915). The Origin of Continents and Oceans. Vieweg+Teubner Verlag.

Hess, H. H. (1962). History of Ocean Basins. In Petrologic Studies: A Volume in Honor of A. F. Buddington (pp. 599-620). Geological Society of America.