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Fossils and Earth's Past

Science

Fossils and Earth's Past Chapter Video

Fossils and Earth's Past Chapter Video

absolute dating

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

carbon film

a thin layer of carbon preserved as a fossil
carbon film Simple Definition

cast

a fossil formed when dissolved minerals fill a mold and harden
cast Simple Definition

eon

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

epoch

a unit of geologic time longer than an age but shorter than a period
epoch Simple Definition

era

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

evolution

the change in a species over time
evolution Simple Definition

extinction

the death of all members of a species
extinction Simple Definition

fossil

the preserved traces and remains of an organism that lived long ago
fossil Simple Definition

geologic time scale

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

half-life

the time it takes for half the atoms of a radioactive isotope to decay
half-life 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

isotope

an atom of the same element with a different number of neutrons
isotope Simple Definition

law of superposition

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

mold

a rock fossil created when a buried organism dissolves
mold Simple Definition

period

a unit of geologic time that lasts tens of millions of years, it is longer than an epoch but shorter than an era
period Simple Definition

radioactive decay

the breakdown of an unstable atomic nucleus, this releases particles and energy
radioactive decay 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

trace fossil

a fossil formed in soft sedimentary rock, like a footprint
trace fossil Simple Definition

unconformity

a gap in a rock layer caused by erosion or periods without sediment deposition
unconformity Simple Definition

uniformitarianism

the theory that geologic processes are the same today as they were in the past
uniformitarianism Simple Definition

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