Chapter 6 Science Voc Words

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

a principle that states that geologic change occurs suddenly

the scientific study of past life, such as fossils

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

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

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

any method of measuring the age of an event or object in years

an atom that has the same number of protons (or the same atomic number) as other atoms of the same element do but that has a different number of neutrons (and thus a different atomic mass)

the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element

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

the time needed for half of a sample of a radioactive substance to undergo radioactive decay

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

a fossilized mark that is formed in soft sediment by the movement of an animal

a mark or cavity made in a sedimentary surface by a shell or other body

a type of fossil that forms when sediments fill in the cavity left by a decomposed organism

a fossil that is found in the rock layers of only one geologic age and that is used to establish the age of the rock layers

the standard method used to divide the Earth's long natural history into manageable parts

the largest division of geologic time

a unit of geologic time that includes two or more periods

a unit of geologic time into which eras are divided

a subdivision of a geologic period

the death of every member of a species