(mya = million years ago)
The times are approximate and may vary by a few million years.
(4567 to 542 mya)
Hadean Eon (4567 to 3800 mya)
(4567 to 3800 mya)
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * - 4650 mya: Formation of chondrules in the Solar Nebula
- 4567 mya: Formation of the Solar System
Sun was only 70% as bright as today.
- 4500 mya: Formation of the Earth.
- 4450 mya: The Moon accretes from fragments
of a collision between the Earth and a planetoid;
Moon's orbit is beyond 64,000 km from the Earth.
Earth day is 7 hours long
- Earth's original hydrogen and helium atmosphere
escapes Earth's gravity.
- 4455 mya: Tidal locking causes one side
of the Moon to face the Earth permanently.
- 3900 mya: Cataclysmic meteorite bombardment.
The Moon is 282,000 km from Earth.
Earth day is 14.4 hours long
- Earth's atmosphere becomes mostly
carbon dioxide, water vapor,
methane, and ammonia.
- Formation of carbonate minerals starts
reducing atmospheric carbon dioxide.
- There is no geologic record for the Hadean Eon.
Archean Eon (3800 to 2500 mya)
(3800 to 2500 mya)
- 3800 mya: Surface of the Earth changed from
molten to solid rock.
- Water started condensing in liquid form.
- Earth day is 15 hours long
- 3500 mya: Monocellular life started (Prokaryotes).
First known oxygen-producing bacteria:
cyanobacteria (blue-green algae) form stromatolites
- 3000 mya: Atmosphere has 75% nitrogen,
15% carbon dioxide.
- Sun brightens to 80% of current level.
- Oldest record of Earth's magnetic field.
Proterozoic Eon (2500 to 542 mya)
(2500 to 542 mya)
Paleoproterozoic Era (2500 to 1600 mya)
Siderian Period (2500 to 2300 mya)
- Stable continents first appeared.
- 2500 mya: First free oxygen is found
in the oceans and atmosphere.
- 2400 mya: Great Oxidation Event,
also called the Oxygen Catastrophe.
Oxidation precipitates dissolved iron
creating banded iron formations.
Anaerobic organisms are poisoned by oxygen.
- 2400 mya: Start of Huronian ice age
Rhyacian Period (2300 to 2050 mya)
- 2200 mya: Organisms with mitochondria
capable of aerobic respiration appear.
- 2100 mya: End of Huronian ice age
Orosirian Period (2050 to 1800 mya)
- Intensive orogeny (mountain development)
- 2023 mya: Meteor impact, 300 km crater
Vredefort, South Africa 
- 2000 mya: Solar luminosity is 85% of current level.
- Oxygen starts accumulating in the atmosphere
- 1850 mya: Meteor impact, 250 km crater
Sudbury, Ontario, Canada 
Statherian Period (1800 to 1600 mya)
- Complex single-celled life appeared.
- Abundant bacteria and archaeans.
Mesoproterozoic Era (1600 to 1000 mya)
Calymmian Period (1600 to 1400 mya)
- Photosynthetic organisms proliferate.
- Oxygen builds up in the atmosphere above 10%.
- Formation of ozone layer starts blocking
ultraviolet radiation from the sun.
- 1500 mya: Eukaryotic (nucleated) cells appear.
Ectasian Period (1400 to 1200 mya)
- Green (Chlorobionta) and red (Rhodophyta) algae abound.
Stenian Period (1200 to 1000 mya)
- 1200 mya: Spore/gamete formation indicates
origin of sexual reproduction.
- 1100 mya: Formation of the supercontinent Rodinia
Neoproterozoic Era (1000 to 542 mya)
Tonian Period (1000 to 850 mya)
- 1000 mya: Multicellular organisms appear.
- 950 mya: Start of Stuartian-Varangian ice age
- 900 mya: Earth day is 18 hours long.
The Moon is 350,000 km from Earth.
Cryogenian Period (850 to 630 mya)
- 750 mya: Breakup of Rodinia and
formation of the supercontinent Pannotia
- 750 mya: End of last magnetic reversal
- 650 mya: *Mass extinction of 70% of dominant sea...
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