Structural control of flank volcanism in continental rifts.

Many volcanoes emerge from the flank (footwall) of normal faults in continental rift zones. Because such locations are commonly topographically high and exhibit minor compressional structures, the association is enigmatic. A simple flexing plate model shows that deformation of a flexurally supported upper crust during normal faulting generates a dilational strain field in the footwall at the base of the crust. This strain field allows cracking and tapping of preexisting melt.