biology

Topics: Extinction event, Antarctica, Ice age Pages: 15 (2956 words) Published: May 30, 2014
(mya = million years ago)
The times are approximate and may vary by a few million years.

Precambrian Time
(4567 to 542 mya)
 
 
Hadean Eon (4567 to 3800 mya)
 
 
Hadean Eon
(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.[33]
    Earth day is 7 hours long[34]
 - 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.[30]
 - 3900 mya: Cataclysmic meteorite bombardment.
    The Moon is 282,000 km from Earth.[34]
    Earth day is 14.4 hours long[34]
 - 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)
 
 
Archean Eon
(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)
 
 
Proterozoic Eon
(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.[14]
    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 [9]
 - 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 [9]
   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.[36]
 - 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.[31]
   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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