Chapter 7 – Thin-skinned Plate Tectonics: The Re-Invention of a Crazy Idea

Publisher Summary The plate-tectonic theory postulates that mountain ranges are formed as a result of plate-to-plate collisions, where the lithosphere plates remain intact and have been subducted. Geophysical investigations in the Alps revealed the velocity structure in the earth's crust, with low velocity channels at or near the Moho. There is also an absence of deep-seated earthquakes, implying the absence of a Benioff Zone. These facts led to the conclusion that the crustal layers were detached from the underlying mantle of lithospheric plates during orogenic deformations. The theory of thin-skinned plate tectonics was dismissed as a crazy idea in the late 1970s. The Swiss National Research Programme 20 (NRP 20) carried out a series of seismic traverses across the Swiss Alps. All major traverses in the east, west, and south show prominent Moho reflections and strong intracrustal energy returns. Interpretations by NRP 20 clearly indicate Moho detachment as well as imbrications of crustal slices. The postulate of thin-skinned plate tectonics is thus no longer a crazy idea.