Yes, tectonic plates (like everything that exhibits large-scale motion on the Earth) are affected by Coriolis forces; they have a tendency to rotate clockwise in the Northern hemisphere, counterclockwise in the Southern. However, the fact that the plates are solid mitigates this effect, as does the fact they run up against each other (like two meshed gears can't both rotate the same way).Originally Posted by Thurlor
However, the Coriolis effect is not the primary cause of the east-west pattern in weather systems. That is the division of the atmosphere into convection cells; six bands along the Earth where hot air rises at one latitude, travels north and south high in the atmosphere, then sinks at a different latitude. The tropical cell is driven by hot air rising at the equator and falling in the subtropics; the polar cell is driven by cold air falling at the poles and rising in subpolar latitudes. The third cell in each hemisphere is the temperate cell, which runs in the opposite direction from what you'd expect, because it's driven by the other two; the air falling from the tropical cell moves towards the pole, then pulled up when it meets the air from the polar cell. (There's a pretty good illustration here.)
Because of the Coriolis effect, the circulation of air in the convection cells causes general air movements along lines of latitude, especially in the mid-latitudes (where the tropical cell meets the temperate cell). However, the convection effect is nonexistent in the tectonic plates; even in the mantle, which has some effect on the motion of the plates, the convection cells are a lot deeper (as there's a lot more mantle than atmosphere) and aren't smeared out into bands by the Earth's rotation.
Basically, then, the Coriolis effect should be, at most, only a minor influence on the motion of the tectonic plates, and you shouldn't expect to see more east-west than north-south motion in any event.
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