Obduction

Obduction is the overlapping of a continental crust by oceanic crust. Obduction results in a continental plate being forced into the asthenosphere, where it will begin to liquefy. The resulting pressure may be released through a volcanic eruption. In addition, the pressure exerted on the plates may cause buckling some distance from the plate boundaries, this results in upthrust mountain ranges.

It can be the consequence of a particular evolution: transformation of a oceanic dorsal into a subduction zone, resorption of the oceanic field, confrontation of the continent and subduction resulting in the expulsion of the oceanic crust on the continent (New Caledonia).It is the only place where it is given to observe in three dimensions, a oceanic fragment of crust. The characteristics rocks of the obducted oceanic crust are the ophiolites (a whole set of rocks going from the basalts and gabbros to the peridotites). Their study brought fundamental information on the nature of the deformations of the mantel rocks, on the displacement of the matter in the higher part of the asthenosphere and on the formation of the magmatic diapirs.

Obduction is not very frequent.