Tectonic Aneurysm  Cartoon showing processes invoked by "tectonic aneurysm" model for development of metamorphic massifs in mountain belts. Deep incision by a river lowers strength of crust, leading to failure into the river valley. This diverts strain and leads to rapid advection of rocks, steeping thermal gradient in crust and maintaining weak zone. Removal of advected material is facilitated by proximity of steep slopes to major river. Alterations of thermal profile also leads to low-pressure high-temperature metamorphism of strained rocks as they are diverted towards surface.

 

Credit: Peter Zeitler

 

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