geologic time scale
Planetary history framework
The geologic time scale is the system used to divide Earth's 4.5-billion-year history into named intervals based on major changes in rock layers, fossils, and planetary events.
It organizes time into eons, eras, periods, and epochs—from the Precambrian through the Paleozoic, Mesozoic, and Cenozoic.
The geologic time scale helps scientists date when dinosaurs went extinct.
Immense time division
- eraDistinct historical period
- periodPunctuation ending sentences
- epochDistinct historical period
- ageDuration of existence
Precambrian · Paleozoic · Mesozoic · Cenozoic · Cambrian · Ordovician · Silurian · Devonian
Study of geological ages
- radiometricMeasuring by radiation
- stratigraphyStudy of rock layers
- isotopeElemental variant by mass
- uranium-leadIsotopic age-determination method
potassium-argon · carbon dating · absolute dating · relative dating · half-life · decay · superposition · correlation
Preserved ancient organism traces
- strataParallel geological layers
- sedimentaryFormed from deposited material
- paleontologyStudy of ancient organisms
- trilobiteExtinct segmented marine arthropod
ammonite · dinosaur · petrified · amber · imprint · shale · limestone · deposition
Large-scale species elimination
- Cambrian explosionSudden appearance of complex life
- orogenyGeological mountain formation
- glaciationIce sheet spreading process
- PangaeaPrehistoric unified landmass
Gondwana · supercontinent · K-Pg boundary · Permian extinction · continental drift · rifting · volcanic · asteroid impact
- MaMillion years ago
- antiquityGreat age, ancient era
- vastnessState of being immense
- prehistoricBefore documented civilization
eon
Immense time division
age · Precambrian · Paleozoic · Mesozoic · Cenozoic · Cambrian · Ordovician · Silurian · Devonian · Carboniferous
geochronology
Study of geological ages
- radiometricMeasuring by radiation
- stratigraphyStudy of rock layers
- isotopeElemental variant by mass
uranium-lead · potassium-argon · carbon dating · absolute dating · relative dating · half-life · decay · superposition · correlation · chronometric
fossils
Preserved ancient organism traces
- strataParallel geological layers
- sedimentaryFormed from deposited material
- paleontologyStudy of ancient organisms
trilobite · ammonite · dinosaur · petrified · amber · imprint · shale · limestone · deposition · unconformity
mass extinction
Large-scale species elimination
- Cambrian explosionSudden appearance of complex life
- orogenyGeological mountain formation
- glaciationIce sheet spreading process
Pangaea · Gondwana · supercontinent · K-Pg boundary · Permian extinction · continental drift · rifting · volcanic · asteroid impact
millions of years
geologic, geology, geological, geologically, geologist, geologists, geo, time, times