GLG 101

Chapter 15

Structural Geology

- deformation: fractured and contorted rocks

- stress: force applied to rock

three types of stress:

- compression: rocks are shortened by folding and faulting

- tension: pull-apart forces

- shear stress: deformation along parallel planes

- strain: deformation caused by stress

two types of strain:

- elastic strain: if object returns to original shape after release of strain

- plastic strain: is beyond elastic strain, rocks fold and fracture

-strike and dip of rocks:

- strike: line of intersection of a horizontal plane and an inclined plane (rock layer)

- dip: measure of maximum angular deviation of an inclined plane from horizontal

strike is measured perpendicular to dip!

folds:

- monoclines

- synclines

- anticlines

- symmetric vs. asymmetric

- plunging folds, overturned folds, recumbent folds

- domes, basins

joints:

fractures along which no movement has occurred

faults:

- fractures along which movement has occurred

- fracture surface is fault plane

- normal vs. reverse (e.g. thrust) fault

- strike-slip fault

Geologic maps:

a topographic map showing rock types (formations) and structures exposed on the surface; legend shows age and composition of rock units, faults are also shown