Alfred Wegener suggested two forces were responsible for the movement of continents:

1. Centrifugal force: He believed the Earth's rotation caused the continents to drift away from the poles like a spinning top.

2. Tidal force: He proposed that the gravitational pull of the sun and moon, particularly on the liquid portion of the Earth, caused a westward drag that moved the continents.

It's important to note that both of these explanations were later proven incorrect. The driving force behind continental drift is plate tectonics, driven by the heat flow from the Earth's interior and convection currents in the mantle.