Pre-Cambrian
Before visible fossils
Pre-Cambrian refers to the vast span of Earth's history before the Cambrian period—roughly 4.5 billion years ago until about 540 million years ago.
This encompasses most of geological time, when life was limited to simple organisms like bacteria and algae.
Pre-Cambrian rocks are among the oldest on Earth.
Also spelled Precambrian.
Immense time division
- eraDistinct historical period
- deep timeImmense spans of Earth's history
- billion yearsThousand million revolutions around sun
- ancientVery old indeed
primordial · earliest · origin · antiquity · geochronology · timescale
Earliest geological eon
- ProterozoicEon before complex life
- cratonStable ancient continental core
- shieldHandheld defensive armor
- gneissFoliated metamorphic rock
schist · zircon · orogeny · tectonics · supercontinent · Pangaea · metamorphic · igneous
Layered sedimentary bacterial structures
- cyanobacteriaPhotosynthetic bacteria producing oxygen
- prokaryotesOrganisms without membrane-bound nuclei
- archaeaThird domain of life
- unicellularOne cell only
anaerobic · chemosynthesis · photosynthesis · abiogenesis · primordial soup · microfossils · algae · bacteria
Layered sedimentary bacterial structures
- microfossilsMinute preserved organism remains
- trace fossilsPreserved signs of activity
- chertFine-grained siliceous stone
- paleontologyStudy of ancient organisms
eon
Immense time division
- eraDistinct historical period
- deep timeImmense spans of Earth's history
- billion yearsThousand million revolutions around sun
ancient · primordial · earliest · origin · antiquity · geochronology · timescale
Archean
Earliest geological eon
- ProterozoicEon before complex life
- cratonStable ancient continental core
- shieldHandheld defensive armor
gneiss · schist · zircon · orogeny · tectonics · supercontinent · Pangaea · metamorphic · igneous · sedimentary
stromatolites
Layered sedimentary bacterial structures
- cyanobacteriaPhotosynthetic bacteria producing oxygen
- prokaryotesOrganisms without membrane-bound nuclei
- archaeaThird domain of life
unicellular · anaerobic · chemosynthesis · photosynthesis · abiogenesis · primordial soup · microfossils · algae · bacteria · mitochondria
stromatolites
Layered sedimentary bacterial structures
- microfossilsMinute preserved organism remains
- trace fossilsPreserved signs of activity
- chertFine-grained siliceous stone
Pre-CambrianCenozoic
Present geological era
Quaternary · modern era · Holocene · recent · Paleozoic