Lithospheric Extension on Venus: how to form narrow rifts

Abstract

The Venusian rifts of Devana and Ganis Chasmata have been noted for their

similar morphology to some rifts on Earth (i.e., the East African rift system). These

are narrow rifts that are associated with localized deformation. This thesis aims to

explore the link between lithospheric structure and rift style using a force analysis

model, following previous work by Buck (1991), in order to determine under what

conditions narrow rifts are predicted for Venus conditions. Results for two cases, one

using a constant lithospheric thermal conductivity and another using a depth

dependent thermal conductivity, are initially determined; Devana and Ganis

Chasmata are predicted to be wide rifts rather than narrow rifts. Lithospheric

weakening mechanisms (rheological weakening and diking) are implemented to

determine their effect on localizing deformation and, thus, forming narrow rifts.

Diking did not produce any effect on forming narrow rifts. Rheological weakening,

likely due to a combination of melt and a transition to grain size sensitive creep,

appears necessary to produce narrow rifts.