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A cavity in rock where a plant or animal was buried.


An object created when sediment fills a mold and becomes rock.


The largest division of geologic time.


The second largest division of geologic time that includes two or more periods.


The third largest division of geologic time.


Subdivisions of periods.


The death of every member of a species.


The scientific study of fossils.


A person who studies fossils.

Geologic time scale

A scale that divides Earth`s 4.6 billion-year history into distinct intervals of time.

Relative dating

Any method of determining whether an event or object is older or younger than other events or objects.


A principle that states that younger rocks lie above older rocks if the layers have not been disturbed.

Geologic Column

an arrangement of rock layers in which the oldest rocks are at the bottom

Absolute dating

the process of establishing the age of an object by determining the number of years it has existed


a surface that represents a missing part of the geologic column


the remains or physical evidence of an organism preserved by geologic processes

Trace fossil

any naturally preserved evidence of animal activity (footprints/tracks or animal droppings)

Index fossil

fossils or organisms that lived during a relatively short, well-defined geologic time span

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