Advertisement Upgrade to remove ads


The preserved remains or traces of an organism that lived in the past


gradual change of the original substances of an organism dissolve and are replaced by minerals from the water (turned to stone)


a type of fossil formed when a shell or other hard part of an organism dissolves, leaving an empty space in the shape of the part


A type of fossil that forms when a mold becomes filled in with minerals that then harden.


hardened tree sap


Thin object falls into sediment can leave an imprint when sediment hardens.

tar pit

Formed when a dark sticky form of oil seep up from underground causing animals to get stuck

trace fossil

a type of fossil that provides evidence of the activities of ancient organisms


a vertebrate animal having four feet or legs or leglike appendages


scientist who studies fossils


to develop gradually by process of growth and change


term used to refer to two-footed locomotion

geologic time scale

scale used by paleontologists to represent evolutionary time

radioactive dating

measurement of the amount of radioactive material (usually carbon 14) that an object contains


a heavy toxic silvery-white radioactive metallic element


The metal created from aged uranium

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

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

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

NEW! Voice Recording