CONTINENTAL BREAKUP
Geometric aspects of continental breakup: How do continents break ?
Pure shear vs simple shear ...
An example of symmetric extension ( the pure shear strain regime is dominant, from Brun and Beslier, 1996). Laboratory experiment, in which relative movement between upper crustal layers is accommodated by layer parallel shear in lower ductile layers. With increased stretching this becomes a decollement between upper crust and the mantle, resulting in mantle exhumation. Note that: 1/ normal faults in the upper crust dip toward the ocean, and 2/ the Moho acts as a décollement surface which accommodates the exhumation of the mantle. On both margins, this décollement dips toward the continent .