Dike Segmentation

-> Dike Segmentation is commonly observed in both ancient dikes exposed by erosion as well as young dikes that have erupted to the surface in historic times

-> Delaney and Pollard (1981) note that a change in the orientation of a dike as it rises towards the surface must indicate a change in the orientation of the principal stresses

-> Two theories have been proposed to explain the rotation of dikes into en echelon segments as they rise to the surface:

1. Intrusion into preexisting fractures (Delaney et al., 1986)
2. Rotation of stresses due to a change from ductile to brittle rheology (Reches and Fink, 1988)