Brittle-Ductile Boundary

-> Proposed by Reches and Fink, 1988

-> High heat flow in the Long Valley Caldera area is created by the presence of a large silicic magma chamber

-> Higher temperatures cause the depth of the brittle-ductile transition to shallow

-> The intrusion of the Inyo dike (shown below) is postulated as follows:

1. the dike propagates from the magma chamber into self-induced extensional fractures
2. when the dike contacts the brittle-ductile transition, the mode of fracturing changes to shearing due to large shear stresses in the shallow crust
3. dilation of and intrusion into shear fractures causes the segmentation and rotation