| A | B |
|---|
| uniformitarianism | the idea that past geologic processes can be explained by current geologic processes |
| James Hutton and Charles Lyell | developed uniformitarianism |
| catastrophism | theory that geologic change occurs suddenly |
| paleontology | the study of past life |
| relative dating | determining whether an object or event is older or younger than another |
| superposition | a principle that states younger rocks lie above older rocks if the layers have not been disturbed |
| geologic column | an arrangement of rock layers in which the oldest rocks are at the bottom |
| tilting | slanting rock layers |
| fault | a break in the Earth's crust |
| folding | rock layers bend and buckle |
| intrusion | melted rock squeezes into exsisting rock |
| unconformity | a break in the geologic record; missing layer |
| disconformity | parallel rock layer is missing |
| nonconformity | sedimentary rock layer lies on top of an eroded surface |
| angular unconformity | found between layers of rock that has been tilted or folded |
| absolute dating | any method of measuring the age of an even or object in numbers of years |
| isotope | an atom that has the same number of protons as other atoms of the same element but do not have the same atomic mass |
| radioactive decay | process in which a radioactive isotope tends to break down into a stable isotope of the same element or a different one |
| radiometric dating | method of determining the age of an object by estimating the number of parent and daughter isotopes |
| half-life | timeline needed for half of a radioactive substance to undergo decay |
| fossil | remains or physical evidence of an organism preserved by geological processes |
| coprolite | preserved animal dung |
| trace fossil | fossilized mark that is formed in soft sediment by the movement of the animal |
| mold | a amrk 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 decomposing organism |
| index fossils | fossils of organisms that lived at a specific time; used to date rocks and other fossils |
| geologic time scale | scale which divides the history of Earth into different time periods |
| eon | largest division of geologic time |
| era | unti of time that includes 2 or more periods |
| period | unit of time that eras are divided into |
| epoch | subdivision of a period |
| extinction | the death of every member in a species |
| Mesozoic era | age of reptiles |
| Paleozoic era | contained the largest mass extinction of all time |
| Cenozoic era | the age of mammals |
