who was responsible for the origin of the terms hanging wall block and footwall block
Tilted block faulting
During extensional time periods , large , gently - dipping normal faults , called detachment faults , can form due to relative separation of the two sides surrounding the fault . Typically , these faults can have an offset on the order of one to tens of kilometers . As the region continues to experience extensive pressures , there is an isostatic effect which moves ductile crust material underneath the fault complex . This fault system can shear the footwall , creating domal mountain ranges , which on a large scale can develop into formations known as metamorphic core complexes . If extension at the surface exceeds about 50 percent , decompression melting may permit magmas to form ; these will deform the footwall , resulting in a complex associated with intrusive and extrusive igneous rocks . Rocks above the detachment fault form normal faults and , at the same time , shear in a `` layer - parallel '' motion . This action creates a series of fault blocks , which are progressively tilted as the detachment fault progresses . The fracturing of the fault blocks can occur in a similar time frame or develop progressively .
During extensional time periods , large , gently - dipping normal faults , called detachment faults , can form due to relative separation of the two sides surrounding the fault . Typically , these faults can have an offset on the order of one to tens of kilometers . As the region continues to experience extensive pressures , there is an isostatic effect which moves ductile crust material underneath the fault complex . This fault system can shear the footwall , creating domal mountain ranges , which on a large scale can develop into formations known as metamorphic core complexes . If extension at the surface exceeds about 50 percent , decompression melting may permit magmas to form ; these will deform the footwall , resulting in a complex associated with intrusive and extrusive igneous rocks . Rocks above the detachment fault form normal faults and , at the same time , shear in a `` layer - parallel '' motion . This action creates a series of fault blocks , which are progressively tilted as the detachment fault progresses . The fracturing of the fault blocks can occur in a similar time frame or develop progressively .