History of Plate Tectonics (Essay Sample)

The History of Plate Tectonics
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Introduction.
Plate tectonics, based on the earlier theory of continental drift proposed by Alfred Wegener is probably the most significant geological theories ever developed. This essay aims to review the evolution of this theory as it has progressed from Wagener’s work to the present.
Continental drift theory
This theory was espoused by Alfred Wegener in 1912. According to Torsvik & Cocks (2012), Wegener, a German meteorologist came up with the proposal that all the continents initially formed a single super-continent which he called Pangea, which was surrounded by a vast ocean called Panthalassa. This supercontinent later drifted apart forming the present day continents. Wegener’s based his theory on the similarity between the coastlines on opposite sides of the Atlantic Ocean. He further expanded his concept on the premise that Permian flora as well as carboniferous fossils were found in South Africa, South America, India, Madagascar, Australia and Eastern Antarctica only and nowhere else leading him to hypothesize that these continents, now separated by oceans, were at one point joined together. Wegener hypothesized that the continents consist mainly of lighter rocks resting on heavier crustal materials and that their relative position is not fixed, but are slowly moving at the rate of approximately a yard per century. He therefore postulated a lateral movement of continents (Torsvik & Cocks, 2012).
A major criticism of Wegener theory is that there was no plausible mechanism to explain the lateral movement of the continents. Further, it would have been expected that due to the lateral movements, there would have been physical evidence of massive thrust faults under the margins of continents, of which none existed further casting doubts on this theory.
Rolf, Coltice & Tackley (2012) affirms, and so do many researchers in this field that the fact that Wagener based much of his arguments on the apparently superficial similarity of symmetry of the coastlines, especially of South America and the West Coast of Africa further weakens his theory. Such a match can only be identified at the continental shelf level hence basing it on coastlines is inherently flawed.
It appears that the major reason why there was much resistance to this theory is because much of Wegener’s work was theoretical in that he dwelt so much on building theories out of his observation as opposed to being empirical which would have involved quantitative applications to support his arguments.
Contemporary plate tectonics theory.
Significant technological advances in the field of geological research especially during and after the Second World War yielded new data which led to the rejection of the vertical movements as proposed by Wegener. As Rolf et al. (2012) succinctly puts it, three main discoveries provided the essential stepping stones in the development of the wider theory of Plate Tectonics, which was largely formulated between 1965 and 1968; Studies of the bathymetry of the ocean floor revealed massive ridges filled with magma from which it was believed the seafloor was spreading, mapping of the earth’s magnetic fields revealed irregular reversals of the magnetic fields polarity while studies of the paleomagnetic data from rocks of the same age from different continents showed different location of poles while that from rocks from different age from same location showed apparent reversal in polarity. The theory arose out of an attempt by geologists to explain these occurances.
According to Rolf et al. (2012), this theory postulates that the earth lithosphere is made up of plates that move relative to each other across the earth. These lithospheric plates consist of seven large and 18 smaller plates that diverge, converge and slip past one another along their boundaries. These plates can be either continental or oceanic or a combination of both and lie atop a layer of partly molten rock called the athenosphere.
The continental plates are mainly made up of granite and are lighter while the oceanic plates are made up of basalt and are denser. The continental plates hence float on top of the oceanic ones high up on the earth’s mantle. The interaction of these plates forms various types of plate bound...