Flash Cards

geo time scale, fossils and dating

Question Answer
Uniformitarianism the principle that states that the same geologic processes shaping the earth today have been at work through Earth's history.
Catastrophism The principle that states that all geologic change occurs suddenly.
Relative Dating Determining whether an object or event is older or younger than other objects or events.
Superposition The principle that states that younger rock lie above older rocks in undisturbed sequences.
Geologic Column an ideal sequence of rock layers that contain all the known fossils and rock formations on earth arranged from oldest to youngest.
Unconformity a surface that represents a missing part of the geologic column.
Fault a break in the earth's crust along which blocks of the crust slide relative to one another.
Intrusion when molten rock from the earth's interior squeezes into existing rock and cools
Folding When rock layers bend and buckle from earth's internal forces.
Tilting when internal forces in the earth slant rock layers without folding them.
Deposition When sediments are deposited and form rock layers.
Disconformity where part of a sequence of parallel rock layers is missing.
Nonconformity where sedimentary rock layers lie on top of an eroded surface of non-layered igneous or metamorphic rock.
Angular Unconformity between horizontal rock layers and rock layers that are tilted or folded.
Absolute Dating The process of establishing the age of an object, such as a fossil or rock layer, by determining the number of years it has existed.
Isotopes atoms of the same element that have the same number of protons but different numbers of neutrons
Radioactive Decay the process of unstable isotopes breaking down stable isotopes of other elements.
Radiometric Dating determining the absolute age of a sample based on the ratio of parent and daughter material.
Half Life the time it takes for one-half of a radioactive sample to decay.
Uranium-Lead Method Half life: 4.5 billion years
for dating: more than 10 million years
Potassium-Argon Method half life: 1.3 billion years
for dating: more than 100,000
Carbon-14 Method half life: 5,730 years
for dating: within last 50,000 years
fossil any naturally preserved evidence of life
types of fossilization 1. fossils in rock (mineral replacement)
2. Fossils in amber
3. mummification
4. frozen fossils
5. fossils in tar
coprolites dung stone
mold a cavity in the ground or rock where a plant or animal was buried
cast shows what the outside of the organism looked like
trace fossils any naturally preserved evidence of an animal's activity.
index fossils fossils of organisms that lived during a relatively short, well-defined time span
Geologic time scale scale that divides earth's 4.6 billion year history into distinct intervals of time.
Geologic time scale (largest to smallest) eon
era
period
epoch
precambrian time 3 eons
phanerozoic eon cenozoic era
mesozoic era
paleozoic era
cenozoic era age of mammals
Mesozoic era age of dinosaurs
Paleozoic era age of first life forms in ocean then on land




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