Geologic Time Vocabulary TEST
Name _____________________________ Period ______
1. ______________________________ A principle that states that the geologic processes that occurred in the past can
be explained by current geologic processes.
2. ______________________________ A principle that states that geologic change occurs suddenly.
3. ______________________________ The scientific study of fossils.
4. ______________________________ Any method of determining whether an event or object is older or younger
than other events.
5. ______________________________ A principle that states that younger rocks lie above older rocks if the layers
have not been disturbed.
6. ______________________________ An arrangement of rock layers in which the oldest rocks are at the bottom.
7. ______________________________ A break in the geologic record created when rock layers are eroded or when
sediments are not deposited for a long time.
8. ______________________________ Any method of measuring the age of an event or object in years.
9. ______________________________ An atom that has the same number of protons (or the same atomic number) as
other atoms of the same element do, but that has a different number of neutrons (and a different atomic mass).
10. ______________________________ The process in which a radioactive isotope tends to break down into a stable
isotope of the same element of another element.
11. ______________________________ A method of determining the age of an object by estimating the relative
percentages of radioactive (parent) isotope and a stable (daughter) isotope.
12. _______________________________ The time needed for half of a sample of a radioactive substance to undergo
radioactive decay.
13. ______________________________ The trace or remains of an organism that lived long ago, most commonly
preserved in sedimentary rock.
14. ______________________________ A fossilized mark that is formed in soft sediment by the movement of an
animal.
15. ______________________________ A mark or cavity made in a sedimentary surface by a shell or other body.
16. ______________________________ A type of fossil that forms when sediments fill in the cavity left by a
decomposed organism.
17. ______________________________ A fossil that is found in the rock layers of only one geologic age that is used to
establish the age of the rock layers.
18. ______________________________ The standard method used to divide the Earth’s long natural history into
manageable parts.
19. ______________________________ The largest division of geologic time.
20. ______________________________ A unit of geologic time that includes two or more periods.
21. ______________________________ A unit of geologic time into which eras are divided.
22. ______________________________ A subdivision of a geologic period.
23. ______________________________ The death of every member of a species.
extinction
uniformitarianism
fossil
catastrophism
half-life
paleontology
radiometric dating
relative dating
radioactive decay
superposition
isotope
absolute dating
geologic column
unconformity
trace fossil
mold
index fossil
epoch
period
era
eon
geologic time scale
cast