The field of science has seen individuals develop various theories to explain certain phenomena. Unlike most people who take the occurrence of certain phenomena for granted, scientists express a lot of interest and take a considerable amount of time to explain why particular things happen. This article seeks to explain the theory of plate tectonics, the scientists behind its development, its evolution over time as well as some of the fundamental terminologies as used to describe the theory.
Summary of the Major Tenets
The plate tectonics theory was first proposed in the 1960s by Alfred Wegener. According to the theory, the earth has an outer layer that is rigid, which is referred to as the lithosphere. The lithosphere is approximately about 100 kilometers thick and covers a plastic layer, which is partially molten known as the asthenosphere. As the theory states, the lithosphere is split into seven large ocean and continental-sized plates, regional plates that are about six or seven in number, as well as , other very small ones. All these plates move relative to each other, approximately at rates of 5 to 10 centimeters every year (Greene, 2015). The interaction of the plates along their boundaries causes the plates to either diverge, converge, or slip past each other.
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Scientists suggest that the interactions of the plates are responsible for the development of most of the earth’s volcanic and seismic activity. Nonetheless, volcanoes and earthquakes can develop in plate interiors. The science community asserts that the motion of plate causes the formation of mountains in areas where plates converge. On the contrary, when plates pull apart, oceans form and the continents fracture (Parks, 2016). Additionally, when continental or oceanic plates move past each other in the same direction or in the opposite direction but at different speeds, they form a transform vault boundary. As such, a new crust is neither formed nor subducted, and also no volcanoes are formed. However, earthquakes occur along the fault.
Most scientists were of the idea that the earth was once a large single landmass. Presumably, features such as the oceans, mountains, as well as, other geographic phenomena had not formed. It is widely accepted among the scientific community that the state of the earth currently is as a result of the action of forces (tectonic forces). These forces must have caused the continental as well as the ocean plates to either converge, diverge or split past each other to form the present features. It is also widely speculated that the plates are constantly either moving towards each other or away from each other.
How the Theory Developed Over Time
New ideas
Initially, the plate tectonics theory only sought to explain that the continents are always moving away from each other. It was even variously referred to as the continental drift theory. However, with time, other new ideas began to sprout up. Apart from proving that the continents are slowly drifting from each other, scientists expanded their scope. Experts now began to use the theory to explain why some phenomena happen in other places and not in others. For instance, the theory was used to explain why volcanoes, mountain ranges, and earthquakes are where they are presently (Erickson, 2014). Also, scientists began to speculate on some of the places that have the likelihood of containing minerals. Therefore, the plate tectonics theory opened up new possibilities and ideas. In the past, people had been faced with calamities such as earthquakes but did not know their cause. Many communities believed in the myth that the calamities were occurring to punish them for their wickedness and perhaps would end if they repented. Unfortunately, the natural disasters happen at some places concurrently and not others. Through the plate tectonics theory, an explanation has been offered and there is a probability that specific regions around the world will still be affected by the disasters.
Role of technology
Perhaps the most crucial aspect that has contributes immensely to the development of the plate tectonics theory is technology. Scientists in the past used primitive and often tedious methods to prove that continental and oceanic plates are constantly moving. However, new technology has changed the way scientists analyze and prove the existence of certain phenomena with regard to the plate tectonic theory. New tools measure and analyze things more accurately than the past techniques. One such tool is known as the strainmeter ( Condie, 2013) . A strainmeter is used to measure the deformation or the change of form of the surface of the earth. Usually, geophysicists use linear strainmeters to measure the change in the distance between two locations. Such a type of strainmeter is used by most scientists trying to monitor the plate tectonics. Instead of trying to prove the validity of the plate tectonics theory by using observable features, scientists can provide empirical evidence in the form of measurements.
Interactions
The plate tectonics theory was not proven by the efforts of a single person, but through collective effort of several scientists. First, it is widely accepted that Alfred Wegener was the proponent of the theory in the start of the 20th century (Sawkins, 2012). He however, referred to the theory as the continental drift because he was mainly interested in explaining how the continents and the oceans were formed. However, Wegener’s theory was later disproved because he failed to explain why the continents moved. Scientists during that time also believed that the formation of various features on the surface of the earth was as a result of the heating and cooling cycles that the earth was subjected to. Nonetheless, the scientific community had been presented with the idea of the movement of the continents that would later become proven through paleomagnetic studies. The examination of the earth’s magnetic field revealed that the magnetic north pole wandered over the globe. Because the North Pole is usually fixed except during moments of magnetic reversals, there was evidence that supported the idea of plate tectonics.
Epistemological factors
For any scientific theory to be accepted, it has to be in tandem with empirical standards or empirical evidence. It means that it ought to be proven beyond doubt. The plate tectonics theory complied with empirical standards particularly following the Second World War when more evidence was uncovered to support the theory. During the 1960s, several seismometers were installed to observe nuclear testing (Johnson, n.d). Measurements showed that volcanoes, earthquakes, as well as other geologic features aligned along particular belts around the globe; hence, those belts defined the edges of tectonic plates. Also, the development of the plate tectonics theory was marred by both skepticism and logical arguments. Wegener expressed his logical arguments by providing evidence of his continental drift theory. He suggested that the theory could be proven through the observation of the continents’ jigsaw fit, the tectonic fit, geological fit, fossil evidence and the glacial deposits. Critics of the theory were skeptic because Wegener could not explain the reason behind the movement of the continents. They still held onto the idea of heating and cooling of the earth until empirical evidence could be provided.
Scientific Contributions
The two major scientific contributions to the plate tectonics theory were that of Harry Hess and Arthur Holmes. Hess graduated with a science degree in Yale University and was a geology enthusiast. While working as commander of the U.S.S Cape Johnson, Hess discovered features on the floor of the ocean that looked like mountains and had flat tops, which he called guyouts (Sawkins, 2012). Hess variously described how hot magma rises from under the crust at the Great Global Rift. After the magma cools, it expands and pushes the tectonic plates apart. Holmes also tried to explain the mechanics behind the movement of the tectonic plates. He posited that the radioactive decay that occurs in the earth’s mantle generates heat; hence, convection currents that cause the continents to move. Holmes used physics to explain geological phenomena and was also obsessed with radiometric dating that allowed him to create his hypothesis.
Influences
As previously stated, the general assumption held by most scientists previously was that the formation of various geographic features was as a result of the cycles of cooling and heating of the earth’s crust. The previous society had also rejected Wegener’s continental drift theory but both Holmes and Hess believed that the theory stood a chance of explaining the occurrence of certain physical features. Hess had previously failed his first class in mineralogy at Yale and had consequently been told that he had slim chances in geology but surprisingly moved on to become one of the most influential people in the plate tectonics theory. Despite Holmes majoring in Physics, he used his knowledge to explain the occurrence of geological features. All the scientists can be said to possess an inquisitive and curious mind.
References
Condie, K. C. (2013). Plate tectonics & crustal evolution . Elsevier.
Erickson, J. (2014). Plate tectonics: unraveling the mysteries of the earth . Infobase Publishing.
Greene, M. T. (2015). Alfred Wegener: science, exploration, and the theory of continental drift . JHU Press.
Johnson, R. L. (n.d.). Plate Tectonics (Revised Edition) . New York: Lerner Digital.
Parks, P. J. (2016). The importance of plate tectonic theory .
Sawkins, F. J. (2012). Metal Deposits in Relation to Plate Tectonics . Berlin, Heidelberg: Springer Berlin Heidelberg.
