Displacement of dipping slabs of lithosphere plates

Abstract

Among the problems arising from the theory of plate tectonics is the question of what happens at the front of a drifting continent where a downgoing slab, being joined with this front, is displaced towards the oceanic side. The slab forms a separating wall, and on its displacement large quantities of the asthenosphere and mesosphere must be moved away from one side and applied to the other side of the horizontally advancing slab. The question is discussed of the behaviour of the material at both sides, and of whether there may be outlets through fractures, or between fragments, of the slab for flow movements from one side to the other. A second question is whether the drifting continental plate causes the displacement or whether, on the contrary, the displacement of the slab causes the drift — at least partially — and may be regarded as a necessary factor of the process which may occur in the same way on island arcs as well as on continental fronts. In other words, there might be a sucking effect or “Pacific attraction” caused by slab displacement and operating on continents as well as on island arcs and the crust behind them, as the present author has repeatedly suggested [1 – 3].