Continental drift, in the context of the modern theory of plate tectonics, is explained by the movement of lithospheric plates over the asthenosphere (the molten, ductile, upper portion of the earth's mantle). Precisely used, the term continental drift is actually rooted in antiquated concepts regarding the structure of the earth. Modern geophyicists and geologists explain the movement or drift of the continents within the context of plate tectonic theory. The visible continents, a part of the lithospheric plates upon which they ride, shift slowly over time as a result of the forces driving plate tectonics. Moreover, plate tectonic theory is so robust in its ability to explain and predict geological processes that it is equivalent in many regards to the fundamental and unifying principles of evolution in biology, and nucleosynthesis in physics and chemistry.

The original theory of continental drift made the improbable assertion...