The theory of plate tectonics has enveloped from Harry’s concept of sea flooring spreading. He proposed this concept in the early 1960’s. The Hess’s hypothesis was accepted when the Vine and Mathews used it in explaining linear magnetic anomalies of the ocean basins. In 1967, WJ Morgan and J.T Wilson extended the idea of Hess and produced the theory of plate tectonics. The factors which led to the theory of plate tectonics were
v Mapping of the ocean floor
v Study of seismic data
v Pattern of anomalies of the earth’s magnetic field
This theory has now offered explanation for many of the complex geological processes such asvolcanic activity, earthquakes, mountain building and continental drift.
The entire earth’s surface is composed of several rigid but relatively thin plates. These plates are between 100-150 kilometers thick and carry both continental and oceanic crust with them. They are in motion with respect to each other.
Almost all seismicity, volcanicity and tectonic activity is localize around plate margins. Henceboundaries between different plates are the particular interest. Depending on the relative motions plates, the plate boundaries are classified into three groups
v Divergent Boundaries
v Convergent Boundaries
v Transform Boundaries
A plate may carry either continental or oceanic crust or both. However only those margins which oceanic crust can participate in the main process of plate growth and destruction