Geologic History Facts

In undisturbed strata, the bottom layer is ______ (law of superposition).

Sedimentary rocks are ALWAYS deposited in ______ layers and underwater (original horizontality).

Any fault, fold, intrusion, that disrupts another layer is (a)   than the rock layer (always younger than the rock layer).

Contact metamorphism occurs when ______ partially melts the rock around it (molten rock).

If an intrusion has no contact meta. (bald) on top it is ______ and was an extrusion (older).

An unconformity was caused by (a)   and weathering (seen as the line that separates crazy layers from straight layers).

Unconformities represent a ______ in the geologic record (gap).

Volcanic ash is a good time marker because it ______ over a large area (spreads out quickly).

Index fossils are found over a wide area and existed for a short period of time.

Radioactive (absolute) dating compares percentage of unstable atoms to stable atoms to get ______ (age of rock).