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Rock Layers Geologic Time MS-ESS1-4

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absolute dating

any method of measuring the age of an object, like tree rings or carbon dating
absolute dating Simple Definition

eon

the largest unit of the geologic time scale, it is divided into eras, periods, and epochs
eon Simple Definition

era

the second-longest unit of geologic time, it is divided into periods
era Simple Definition

fossil record

the history of life recorded by all the fossils we have collected
fossil record Simple Definition

geologic time scale

a timeline of Earth's history based on major changes
geologic time scale Simple Definition

index fossil

a fossil from an organism that existed for a short time, it is used to determine the age of other fossils
index fossil Simple Definition

law of superposition

the oldest rock layers are at the bottom and youngest are at the top
law of superposition Simple Definition

radiometric dating

comparing the amount of radioactive and nonradioactive isotopes to determine rock age
radiometric dating Simple Definition

relative dating

a method of comparing fossils or rocks to determine which is older
relative dating Simple Definition

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