20 terms

Lipold's Geologic History Vocab. 2019

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Law of cross cutting
Any feature that cuts across a rock or body of sediment must be younger than the rock or sediment that it cuts across
absolute time
Method of recording events with actual dates and events.
relative time
Method of recording events in sequence without actual dates.
index fossil
Fossils that help to identify the age of rock; lived for narrow range of time.
half-life
Time required for half of the atoms in a radioactive substance to decay to a daughter substance.
radioactive dating
Uses radioactive decay to determine the age of rock deposits.
relative dating
Uses natural laws to determine the age of rock deposits.
Law of Superposition
States that in layers of undisturbed rock, the oldest rocks will be on the bottom.
Cambrian explosion
earliest part of the Paleozoic era, when a huge diversity of animal species evolved
Law of Inclusions
States that pieces of one rock found in another rock are older than the rock in which they are found.
Law of Folding
States that the wavy lines or folds of rock layers is younger than the layers that are folded.
Fossil
The preserved remains or traces of an organism that lived in the past
petrified fossil
rock forming minerals in groundwater enter the pore spaces or replace the tissues of dead organisms
Unconformity
A break or gap in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
Law of Uniformitarianism
the idea that the same processes we see occurring now also occurred in the past
preserved remains
remains of organisms in tar, amber, or ice
cast
a fossil copy of an organism made when a mold of the organism is filled with sediment or mineral deposits
mold
The impression of an organism in a rock left by an ancient organism
trace fossil
the preserved evidence of the activity of an organism
carbon films
the fossilized carbon outline of an organism or part of an organism