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Fossils and Earth's Past

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

Any Method Of Measuring The Age Of An Object, Like Tree Rings Or Carbon Dating.

Absolute Dating

Absolute Dating Simple Definition

a thin layer of carbon preserved as a fossil

A Thin Layer Of Carbon Preserved As A Fossil.

Carbon Film

Carbon Film Simple Definition

a fossil formed when dissolved minerals fill a mold and harden

A Fossil Formed When Dissolved Minerals Fill A Mold And Harden.

Cast

Cast Simple Definition

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

The Largest Unit Of The Geologic Time Scale, It Is Divided Into Eras, Periods, And Epochs.

Eon

Eon Simple Definition

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

A Unit Of Geologic Time Longer Than An Age But Shorter Than A Period.

Epoch

Epoch Simple Definition

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

The Second-longest Unit Of Geologic Time, It Is Divided Into Periods.

Era

Era Simple Definition

the change in a species over time

The Change In A Species Over Time.

Evolution

Evolution Simple Definition

the death of all members of a species

The Death Of All Members Of A Species.

Extinction

Extinction Simple Definition

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

The Preserved Traces And Remains Of An Organism That Lived Long Ago.

Fossil

Fossil Simple Definition

a timeline of Earth's history based on major changes

A Timeline Of Earth's History Based On Major Changes.

Geologic Time Scale

Geologic Time Scale Simple Definition

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

The Time It Takes For Half The Atoms Of A Radioactive Isotope To Decay.

Half-life

Half-life Simple Definition

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

A Fossil From An Organism That Existed For A Short Time, It Is Used To Determine The Age Of Other Fossils.

Index Fossil

Index Fossil Simple Definition

an atom of the same element with a different number of neutrons

An Atom Of The Same Element With A Different Number Of Neutrons.

Isotope

Isotope Simple Definition

the oldest rock layers are at the bottom and youngest are at the top

The Oldest Rock Layers Are At The Bottom And Youngest Are At The Top.

Law Of Superposition

Law Of Superposition Simple Definition

a rock fossil created when a buried organism dissolves

A Rock Fossil Created When A Buried Organism Dissolves.

Mold

Mold Simple Definition

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

A Unit Of Geologic Time That Lasts Tens Of Millions Of Years, It Is Longer Than An Epoch But Shorter Than An Era.

Period

Period Simple Definition

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

The Breakdown Of An Unstable Atomic Nucleus, This Releases Particles And Energy.

Radioactive Decay

Radioactive Decay Simple Definition

comparing the amount of radioactive and nonradioactive isotopes to determine rock age

Comparing The Amount Of Radioactive And Nonradioactive Isotopes To Determine Rock Age.

Radiometric Dating

Radiometric Dating Simple Definition

a method of comparing fossils or rocks to determine which is older

A Method Of Comparing Fossils Or Rocks To Determine Which Is Older.

Relative Dating

Relative Dating Simple Definition

a fossil formed in soft sedimentary rock, like a footprint

A Fossil Formed In Soft Sedimentary Rock, Like A Footprint.

Trace Fossil

Trace Fossil Simple Definition

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

A Gap In A Rock Layer Caused By Erosion Or Periods Without Sediment Deposition.

Unconformity

Unconformity Simple Definition

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

The Theory That Geologic Processes Are The Same Today As They Were In The Past.

Uniformitarianism

Uniformitarianism Simple Definition

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