EARTH SCIENCE:
Crustal Forces

Deformation: the bending, tilting, and breaking of the earth’s crust.

Isostasy: The balancing of forces: the weight of the crust pushing down on the mantle and the mantle pushing up on the crust.
a. Balancing requires up and down movement- so the crust
raises and lowers in response the this balancing of forces.

Examples: Erosion of mountains
Deposition of sediment at the mouths of rivers
Retreating glaciers: exposed land rises

When the crust adjusts it causes the stress on the rocks.

Stress may produce changes in the shape and volume or size of rocks (strain)

3 types of stress: Compression-rocks squeezed together
Tension-pulls rocks apart
Shearing-forces rocks in two horizontal directions
If the stress is great enough it can break the rock into pieces.

FOLDING: occurs when rocks become permantly deformed without breaking. 3 types: Monocline, Anticline, and Syncline

FAULTING: Movement of two blocks of crustal rock along a crack in the crust. 4 types:

Mountain Formation:
1. Folded mountains: mtns formed by tectonic movements that have been squeezed together like an according.

Plateaus are also formed this way.

2. Fault-block mtns: large crustal blocks that have been lifted above the surrounding crust.

3. Volcanic mtns: this includes both continental and oceanic volcanic mtns.

4. Dome mtns: molten rock forces its way up-forcing the crust to rise. The crustal rock is eroded away leaving the harden (magma) rock above the crust.