Ch 5 Vocab Flashcards
Catastrophism
A principle that states that geologic change occurs suddenly
Uniformitarianism
A principle that geologic processes that occurred in the past can be explained by current geological processes
Relative age
The approximate age of fossils or other objects in rock layers determined by comparing whether the surrounding rock layers are younger or older
Relative dating
Any method of determining whether an event or object is older or younger than other events or objects
Geologic column
And ordered arrangement of rock layers that’s based on the relative ages of the rocks that in which the oldest rocks are at the bottom
Absolute dating
Any method of measuring the age of an event or object in years
Paleontology
The scientific study of fossils
Fossil
The trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock
Trace fossil
A fossilized mark that formed in sedimentary rock by movement of an animal on or within soft sediment
Mold
A mark or cavity made in a sedimentary surface by a shell or other body
Cast
A type of fossil that forms when sediments fill in the cavity left by a decomposing organism
Index fossil
A fossil that’s used to establish the age of a rock layer because the fossil is distinct, abundant, and widespread and the species that formed it existed for only a short span of geological time
Geologic Timescale
The standard method used to divide earth’s long natural history into manageable parts
Eon
The largest division of geologic time
Era
Our unit of geologic time that includes two or more periods
