the remains (or an impression) of a plant or animal that existed in a past geological age and that has been excavated from the soil
gradual change of the original substances of an organism dissolve and are replaced by minerals from the water (turned to stone)
the type of fossil that forms when a mold becomes filled in with minerals that harden. the cast takes on the shape of the mold creating a replica of the organism or part.
geographic time scale
categories of time into which Earth's history is divided by geologists and paleontologists: eons, eras, periods, epochs
the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products
a white, radioactive metallic chemical element that weighs more than any other element in nature.