Timeline of Oxygen in the Atmosphere
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Major Events |
Air / Climate |
Life |
More |
A |
|
- oceans in the air - no life yet |
- 80% H2O - 10% CO2 - 5-7% H2S
- Very Hot (Lava) |
- no life yet |
- tumultuous lava flows steam off any water |
B |
|
- early life - oxygen can't accumulate yet |
Intermittant Oxidation
- Snowball Earth |
- microscopic life, including algae |
- except during Ice Ages, surface metals are oxidized and absorb all available oxygen |
C |
|
- multicellular life |
- O2 up - CO2 up
- Warm and Humid |
- strange plants and animals different from modern life |
- surface metals fully oxidized, so oxygen can now accumulate in atmosphere |
D |
|
- plants spread on land |
- O2 stable - CO2 stable
- Warm, Wet and Mild |
- Trilobites, Snails, Fish - Moss and Early Plants on land |
- plants and animals reach equilibrium, plants oxygen output is consumed by animal life |
E |
|
- early trees and ferns |
- O2 up - CO2 down
- Arid to Warm Temperate |
- Trees and Ferns - Insects, Amphibians |
- plants colonize land, increase oxygen and deposit carbon |
F |
|
- plants evolve bark - much oxygen produced |
- O2 up a lot - CO2 down a lot
- Cool and Wet |
- Plants evolve bark (8 bark to 1 wood!), nothing can eat it yet - Giant Insects + Amphibians |
- plants evolve lignin (lotsa bark), thus temporary plant supremacy, even more oxygen, more carbon deposit - industrial age coal comes from here |
G |
|
- (pangea) single continent - hostile climate |
- O2 drops a lot - CO2 low
- (Pangea) Single Continent - Cool,
Very Dry - Seasonal Rain |
- Conifers - Cockroaches, Reptiles |
- desert too dry for many plants, so oxygen drops, carbon gap (very little deposit) |
H |
|
- dinosaurs |
- O2 up - CO2 up
- Warm and Humid |
- Cycads and Ferns - Dinosaurs |
- warm humid climate favorable to plants, so oxygen rises again |
I |
|
- no polar ice caps - hothouse climate lets plants produce more oxygen |
- O2 up - CO2 down
- Max Oceans (2/3 as much land) - Hot and Wet - even at the poles |
- Grass and flowers evolve - Dinosaurs - early Birds and Mammals |
- no polar ice caps - hothouse climate lets plants make more oxygen, deposit more carbon - shelled plankton deposit chalk on ocean bottom, reducing CO2 |
J |
|
- birds and mammals - a few ice ages |
- O2 down - CO2 down
- Cooling - some Ice Ages |
- Savannah - Mammals and Birds |
- ice caps return, and several ice ages - lower oceans - grasses dominate - fewer plants, so oxygen goes down |
K |
|
- humans - terraforming |
- CO2 up - methane up a lot
- most stable climate ever, suitable for agriculture |
- Humans! |
- Humans dig up and burn fossil fuels, depleting atmospheric oxygen and increasing CO2 |