Question | Answer |
principle that states that geological process shaping the Earth today have been at work throughout Earth's history | uniformitarianism |
principle that states that all geological change occur suddenly | catastrophism |
paleontology | the science involved with the study of past life |
relative dating | determining whether an object or event is older or younger than other objects or events |
geologic column | an ideal sequence of rock layers that contain all the known fossils and rock formations on earth, arranged from oldest to youngest |
absolute dating | the process of establishing the age of an object by determining the number of years it has existed |
isotope | atoms of the same element that have the same number of protons but have different numbers of neutrons |
radioactive decay | isotopes tend to break down into stable isotopes of the same or other elements |
half-life | the time needed for half of a sample of a radioactive substance to undergo radioactive decay |
fossil | remains or physical evidence of an organism preserved by geologic process |
petrifaction | process in which minerals replace on organisms tissue |
trace fossil | 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 |
index fossil | a fossil that is found in the rock layers of only one geological age and that is used to establish the age of the rock layers |
geologic time scale | standard method used to divide the Earth's long natural history into manageable ports |
eon | largest division of geologic time |
era | unit of geologic time that includes two or more periods |
periods | unit of geologic time into which eras are divided |
extinction | the death of every member of a species |