Fossil Record Vocab Flashcards
uniformitarianism
a principle that states that geologic processes that occurred in the past can be explained by current geologic processes
catastrophism
a principle that states that geologic change occurs suddenly
paleontology
the scientific study of fossils
relative dating
any method of determining whether an event or object is older or younger than other events or objects
absolute dating
any method of measuring the age of an event or object in years
superposition
a principle that states that younger rocks lie above older rocks if the layers have not been disturbed
isotope
an atom that has the same number of protons as other atoms of the same element do but that has a different number of neurons
radioactive decay
the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element
half-life
the time needed for half of a sample of a radioactive substance to undergo radioactive decay
fossil
the remains or physical evidence of an organism preserved by a geological process
trace fossil
a fossilized mark that is formed in soft sediment by the movement of an animal
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 decomposed organism
unconformity
a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
mass extinction
a complete extinction of a group of organisms
