| A | B |
|---|
| principle of uniformitarianism | states that all present geolgical processes are same processes as in past |
| James Hutton | theorized that forces at work were the same as those in the past |
| strata | layers of rock |
| relative age | tells age in relation to others around it |
| bedding plane | boundary between two layers of rock |
| law of superposition | states that undisturbed sedimentary rock is older than layers above and younger than those below |
| ripple marks | small waves in rock formed by wind and water |
| unconformity | period in which deposition stopped and erosion started leaving a break in geologic record |
| nonconformity | unconformity in which stratified rock sits upon unstratified |
| angular unconformity | rock layers are folded or tilted and new layers deposited on top |
| disconformity | horizontal layers rest on top of eroded horizontal layers, leaving a gap in the rock record |
| law of crosscutting relationships | states that a fault or intrusion is youger than layers it cuts through |
| absolute age | actual age of a rock layer |
| varves | annual layers of sediment that form in lakes and can be counted to tell age of rock |
| radioactive | elements that emit particles and energy |
| radioactive decay | process in which elements emit particles and change into different elements |
| Pb-206 | end product in the decay of U-238 |
| parent element | the element that starts radioactive decay |
| daughter element | the final product of radioactive decay |
| half-life | time it takes for half the mass of a given amount of an radioactive |
| Carbon-14 | decays into Nitrogen-14 and can be used to date anything once living |
| paleontologists | study fossils to learn about past |
| evolution | change of living things over time |
| paleontology | study of fossils |
| mummification | drying of organisms to produce fossils |
| amber | hardend tree sap |
| tar beds | thick accumulation of petroleum that traps and preserves organisms |
| freezing | preservation of organisms through low temperatures |
| petrification | process in which minerals replace organic material |
| trace fossils | tracks, footprints, etc. in which only parts of organisms remains |
| imprint | displays the surface features of organism |
| mold | retains shape and surface markings of organism |
| cast | replica of outer surface of organism |
| coprolites | fossilized fecal matter |
| gastroliths | stones that helped dinosaurs with digestion |
| index fossil | fossil that is used to determine the age of a specific rock layer |
| ammonite | marine organism that serves as the index fossil for Jurassic/Cretaceous Periods |
| trilobite | marine fossils that serves as index fossil for Mesozoic Era |
