Advertisement Upgrade to remove ads


a principle that geologic processes that occurred in the past can be explained by current geologic processes.

Relative Age

the age of an object in relation to the ages of other objects.

Law of Superposition

the law that a sedimentary rock layer is older than the layers above it and younger than the layers below it if the layers are not disturbed.


a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.

Law of Crosscutting Relationships

the principle that a fault or body of rock is younger than any other body of rock that it cuts through.

Absolute Age

the numeric age of an object or event, often stated in years before the present, as established by an absolute-dating process, such as radiometric dating.


a banded layer of sand and silt that is deposited annually in a lake, especially near ice sheets or glaciers, and that can be used to determine absolute age.

Radiometric Dating

a method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope.



Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!



Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom


Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

Voice Recording