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Kinds of Faults. Faults. Is a break in Earth’s crust where slabs of crust slip past each other. Usually occur along plate boundaries , where the forces of plate motion compress, pull, or shear the crust so much that the crust breaks. Three Types of Faults. Normal Faults Reverse Faults
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Faults • Is a break in Earth’s crust where slabs of crust slip past each other. • Usually occur along plate boundaries , where the forces of plate motion compress, pull, or shear the crust so much that the crust breaks.
Three Types of Faults • Normal Faults • Reverse Faults • Strike-Slip Faults
Fault Terminology • Fault Plane - the plane along which the rock or crustal material has fractured • Hanging Wall Block - the rock material which lies above the fault plane • Footwall Block - the rock material which lies below the fault plane.
Hanging vs. Foot • The footwall of a fault is always under the fault • The hanging wall of a fault is always above the fault
Normal Faults • Caused by tension forces where plates diverge • The fault is at an angle • One block lies above the fault (hanging wall) • The other block lies below the fault (footwall) • When movement occurs along a normal fault, the hanging wall slips downward
Normal Fault Footwall Hanging Wall
Reverse Faults • Caused by compression forces along convergent plate boundaries • Has the same structure as a normal fault, but blocks move in opposite direction • One side lies at an angle above the other • Where the hanging wall is displaced upward relative to the footwall • OR where the footwall is displaced downward relative to the hanging wall
Reverse Fault Hanging Wall Footwall
Strike-Slip Fault • Created by shearing along transform boundaries • Rocks on either side of fault slip past each other sideways with little up-or-down motion
Whose Fault? Side View
Whose Fault? Side View
Whose Fault? Birds-eye View
Whose Fault? Side View
Whose Fault? Side View
Whose Fault? Birds-eye View
Whose Fault? Side View