Term | Definition |
Law of superposition | undisturbed layers get younger as you go up |
principle of original horizontality | all beds originally deposited in water form close to horizontally |
principle of cross-cutting relationship | when a fault cuts through rock, the rock is younger |
inclusions | pieces of one rock unit contained within another |
conformable | strata sequence that is undisturbed |
unconformities | gaps in geologic time that indicate erosion, deformation |
disconformities | large gap in geologic time due to processes of erosion |
angular unconformities | younger strata overlie an erosion surface on tilted or folded rock |
nonconformities | igneous or metamorphic magma chamber intrudes, then erosion erodes |
petrification | turn to stone (LOOKS LIKE WOOD) |
replacement | cell membrane are removed and replaced with mineral matter |
mold | reflects the shape and surface marking |
cast | a mold that is filled in with mineral matter and solidified |
carbonization | carbon film left behind after organism decay (PLANT) |
impression | carbonization process, carbon lost and replica of surface |
amber | resin from trees, insects are preserved (WHOLE ORGANISM) |
tracks | animal footprints in sediment later solidified |
coprolites | fossil poo and stomach contents that were preserved |
gastroliths | polished stomach stones |
burrows | tubes in sediment, wood, or rock made by an animal |
rock and fossil correlation | matching of rock layers from one location at the same time to another location |
principle of fossil succession | older rock contain fossils that are increasingly different from modern species |
fossil assemblage | several different species found together in a specific rock unit |
index fossil | well defend morphological characteristics (short-lived species and widespread distribution |
radiometric dating | calculating the absolute ages of rock and minerals that contain radioactive isotoped |
alpha emission | atomic #= -2
mass # -4 |
beta emission | atomic #= +1
mass # unchanged |
electron capture | atomic # = -1
mass #= unchanged |
half-life | time required for half of the nuclei in a sample to decay |
radiocarbon dating | date recent events (carbon -14) |
half life of carbon014 | 5730 yrs |
half life of uranium-238 | 4.5billion years |
numerical dating | actual number of yrs |
how do geologists numerically date rocks | radioactive decay |
relative dating | events in their proper sequence |
biggest era | paleozoic |
present era | cenozoic |
present eon | phanerozoic |
present epoch | holocene |
present period | quaterary |
what eon means visible life | phanerozoic |
uniformitarianism | the physical chemical and biological laws that operate today have also operated in the geologic past (long history of earth) |
catastrophism | earth's landscape has been developed by worldwide disasters (over a short span)(catastrophism does not require assumptions of long timelines) |