Fault and Folds Deformation of the Crust Isostasy

Fault and Folds: Deformation of the Crust

Isostasy (A) When gravitational and buoyant forces are equal, a state of isostasy exists. (B) As erosion wears away the crust, the lithosphere becomes lighter and rises. (C) As erosion continues, the isostatic adjustment also continues.

Isostasy • Subsidence occurs when sediments are quickly deposited and compacted. • Glaciers also change Isostasy.

Faults • Where two tectonic plates or pieces of Earth’s crust slide past each other. • Tension or pressure build up along fault zones • When pressure gets to high, the fault slips. • Faults slipping cause EARTHQUAKES!!!

Faults of Virginia

Types of Faults • 3 Types: Normal Fault, Reverse (thrust) fault, and Transform (Strike-Slip) Fault.

Normal Fault • Tension or pulling apart causes headwall (hanging wall) to slide down footwall. • Crust is lengthened. • Divergent boundary

Reverse or Thrust Fault • Headwall is thrust up over the footwall due to compression. • Crust is shortened. • Convergent Boundary

Transform (Strike-Slip) Fault • One plate slides past the other. No headwall or footwall. • Example: San Andreas Fault • No crust shortening or lengthening. • Shearing (tearing) is present. • Transform Boundary (it transforms the crust by folding it).

What kind of fault is this?

What kind of fault is this?

What kind of fault is this?

Folds • Faulting often causes folding of rock to form Mountains. • The Appalachian Mountains in Virginia are faulted and folded. • 2 Types of Folds: Anticlines and Synclines