Geologic time vocabulary review Correlation Determining time equivalency

Geologic time vocabulary review

Correlation Determining time equivalency of rock units.

Eon Largest unit of geologic time.

stock sill dike neck Cross-cutting relationship A disrupted pattern is older than the disruption.

Fossil Traces of plants or animals preserved in rock.

Half life The time it takes for a radioactive isotope to be reduced by 1/2.

Angular unconformity A type of unconformity in which layers overlie tilted or folded rocks.

Paleozoioc era The era that followed the Precambrian. The appearance of complex life.

Mesozoic era This era follows the Paleozoic and precedes the Cenozoic.

Index fossil Short-lived fossils from a specific time.

Formations Thick rock layers that are easily distinguished from adjacent layers.

Faunal succession Fossils succeed one another in a definite order.

Isotope Atoms with different numbers of neutrons, but the same number of protons.

Epochs Time periods are subdivided into these.

Eras Major subdivision of the geologic time scale.

Disconformity A type of unconformity in which layers are parallel to each other.

stock sill dike neck 10, 000 ± 300 Numeric age Age given in years.

Periods Each era is subdivided into these.

Radioactive decay The disintegration of certain isotopes.

stock sill dike neck Relative time The sequence in which events took place.

Nonconformity A type of unconformity where igneous rock has been covered by younger sedimentary rock.

Uniformitarianism “The present is the key to the past. ”

Cenozoic era The most recent era; followed the Mesozoic era.