Final answer:
Continental drift refers to the movement of Earth's crustal plates on the mantle, a concept now largely encompassed by the theory of plate tectonics, which contributes to large-scale geologic activities and is driven by mantle convection.
Step-by-step explanation:
The correct option that accurately describes continental drift is A: Crustal plates floating on the mantle change position relative to one another.
Continental drift is a theory that has been replaced by the more comprehensive theory of plate tectonics. Plate tectonics explains how slow motions within the Earth's mantle move large segments of the crust.
This movement, which happens at a rate of millimeters to a few centimeters per year, causes continents to gradually 'drift' and is also responsible for the formation of mountains and other geological features.
Alfred Wegener, a German meteorologist and astronomer, was the scientist who made the case for continental drift in 1920.
He noticed that the coasts of Americas and Europe and Africa seemed to fit together, suggesting that the continents were once joined and had drifted apart over time.
The movement of tectonic plates is powered by convection within the mantle, where heat from the interior is transported to cooler regions, such as the surface.
There are three main types of plate boundaries: divergent, where plates are moving apart; convergent, where plates are moving towards each other; and transform, where plates are sliding past each other.