geologic time
Earth's vast chronology
Geologic time is the vast timescale of Earth's history, measured in millions and billions of years rather than human lifespans.
Geologists divide it into eons, eras, periods, and epochs based on rock layers and fossil records: The Grand Canyon exposes nearly two billion years of geologic time.
The phrase emphasizes duration beyond human comprehension—mountains rise and erode, continents drift, species appear and vanish.
Immense time division
- eraDistinct historical period
- periodPunctuation ending sentences
- epochDistinct historical period
- ageDuration of existence
Precambrian · Paleozoic · Mesozoic · Cenozoic · Cambrian · Ordovician · Silurian · Devonian
Formation of distinct species
- adaptationFitting to new conditions
- diversificationExpanding into varied areas
- phylogenyEvolutionary relationships among organisms
- lineageDescent from progenitors
ancestry · descent · natural selection · radiation · origination · extinction · tree of life · common ancestor
Extinct segmented marine arthropod
- ammoniteExtinct spiral-shelled cephalopod
- dinosaurExtinct Mesozoic reptile
- archaeopteryxEarly feathered dinosaur genus
- petrifiedSolidified or fear-paralyzed
paleontology · extinction · preserved · sedimentary · amber · biomarker · fauna · flora
Age measurement via atomic decay
- carbon datingIsotope-based age measurement
- stratigraphyStudy of rock layers
- half-lifePeriod for fifty-percent reduction
- isotopeElemental variant by mass
uranium-lead · potassium-argon · dendrochronology · golden spike · unconformity · correlation
Thousand million revolutions around sun
- million yearsOne thousand millennia
- MaMillion years ago
- antiquityGreat age, ancient era
- immensityLimitless extent or magnitude
abyss · unfathomable · vastness · timescale · cosmic · planetary · age of Earth · incomprehensible
Large-scale species elimination
- Cambrian explosionSudden appearance of complex life
- K-Pg boundaryGeological extinction horizon
- Permian extinctionDeadliest extinction event ever
- ice ageEra of massive glaciation
glaciation · orogeny · rifting · volcanism · asteroid impact · supercontinent · Pangaea · Gondwana
eon
Immense time division
age · Precambrian · Paleozoic · Mesozoic · Cenozoic · Cambrian · Ordovician · Silurian · Devonian · Carboniferous
speciation
Formation of distinct species
- adaptationFitting to new conditions
- diversificationExpanding into varied areas
- phylogenyEvolutionary relationships among organisms
lineage · ancestry · descent · natural selection · radiation · origination · extinction · tree of life · common ancestor · evolutionary history
trilobite
Extinct segmented marine arthropod
- ammoniteExtinct spiral-shelled cephalopod
- dinosaurExtinct Mesozoic reptile
- archaeopteryxEarly feathered dinosaur genus
petrified · paleontology · extinction · preserved · sedimentary · amber · biomarker · fauna · flora
radiometric dating
Age measurement via atomic decay
- carbon datingIsotope-based age measurement
- stratigraphyStudy of rock layers
- half-lifePeriod for fifty-percent reduction
isotope · uranium-lead · potassium-argon · dendrochronology · golden spike · unconformity · correlation
billion years
Thousand million revolutions around sun
- million yearsOne thousand millennia
- MaMillion years ago
- antiquityGreat age, ancient era
immensity · abyss · unfathomable · vastness · timescale · cosmic · planetary · age of Earth · incomprehensible · secular
mass extinction
Large-scale species elimination
- Cambrian explosionSudden appearance of complex life
- K-Pg boundaryGeological extinction horizon
- Permian extinctionDeadliest extinction event ever
ice age · glaciation · orogeny · rifting · volcanism · asteroid impact · supercontinent · Pangaea · Gondwana
- earth scienceatmosphere, earthquake, volcano, crust, eruption
- geologybedrock, fault lines, faults, rock, basalt
- Earth historyice age, extinction, eons, fossil, epochs
- geologic timeeons, eon, epochs, era, epoch
- Geochronologytimescale, eon, eons, era, eras
- evolutionevolution, natural selection, mutation, adaptation, speciation
geologic timehuman history
Record of civilization's events
recorded history · instantaneous · lifetime · momentary · fleeting
geologic, geology, geological, geologically, geologist, geologists, time, times, timed