Glossary of Geology Terms Used

Alluvium - Unconsolidated gravel, sand, and finer rock debris deposited principally by running water. Found locally on the floors of canyons and valleys.

Anticline - a fold in layered rock, convex upward, with older rocks toward the core.

Basement Complex - the surface beneath which sedimentary rocks are not found; the igneous, metamorphic, granitized, or highly deformed rock underlying sedimentary rocks.

Bedding Plane - the dividing plane that separates each layer in a sedimentary or stratified rock from layers below and above it.

Coast Ranges Orogeny - A time, mostly during the late Pliocene, of major deformation (mostly mountain building and faulting), metamorphism, and volcanic activity in the Coast Ranges in California.

Disconformity - an unconformity in which the beds above and below an erosion surface are concordant.

Facies - an assemblage or association of mineral, rock, or fossil features reflecting the environment and conditions of origin of the rock.

Headward Erosion - the lengthening of a valley or gully, or of a stream, by erosion at the valley head

Orogeny - period of intense mountain building by way of folding, thrusting, or volcanism

Perennial - year round

Syncline - a downward fold in layered rock, primarily sedimentary rocks, caused by compression forces ; opposite of an Anticline

Terrace - Step-like landform consisting of a flat tread and a steep riser, commonly of fluvial (river), lacrustine (lake), or marine origin.

Thrust Fault or Zone - Gently inclined reverse fault along which one block is thrust over the other.