Two models could be used to characterize extensional deformation: simple shear and pure shear. Pure shear produces symmetric crustal thinning along the axis of the rift. As a contrast, simple shear gives an assymetric crustal thinning and a large low angle detachment fault associated with thinning in the lithosphere (Wilson et al, 2004).

Edge Driven Convection

Small scale convection is introduced by Wijk et al. (2008) This small scale convection does not start until the lithosphere has been thinned sufficiently to produce a lateral thermal gradient. This edge driven convection produces a downward flow in the eastern side of the rift itself.