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Geologic Time

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)
Created by: miabegic2