Graben Formation and Dike Emplacement on Earth and Other Planets

INTRODUCTION Dike emplacement has become an increasingly popular means to form grabens radiating from a volcanic centre in the recent planetary geology literature, on Venus [1-3] and on Mars [4-8]. The Tharsis example is used to clarify two important issues that have been scarcely discussed: what evidence of dike emplacement beneath the grabens in the examples mentioned in these papers can be found; and if dikes do actually exist beneath these grabens, what is the role of magma pressure and that of remote stress in graben initiation and development.