1. Story Board Oxygen in the Atmosphere 66 67 Early Earth Atmosphere
Cyanobacteria and Photosynthesis
Oxygen accumulation
Atmosphere Today 66 67

3. Warm up Review: What gasses were present in Early Earths Atmosphere?
Early atmosphere [H, He, Ammonia (NH3) and Methane (CH4)] was driven away by solar radiation and lost by their low atomic masses

4. EQ: What role does cyanobacteria have on the atmosphere?

5. Slide 1 of 7
Primordial Earth melted completely, and gases bubbled out or erupted from early volcanoes. Result was a N-rich atmosphere

6. Slide 2 of 7
Evolution of blue-green algae, aka Cyanobacteria, changed everything! Photosynthesis by these algae uses sunshine, H2O, and CO2 and produces carbohydrates and O2

7. Discovery Science Still Happening!
In a field research done in Lake Fryxell, Antarctica, researchers found out that mats of oxygen-producing cyanobacteria can produce a thin layer, one or two millimeters thick, of oxygenated water that had an oxygen depleted environment
Thus, before oxygen started accumulating in the atmosphere, these organisms could have possibly adapted to oxygen.

8. Slide 3 of 7
In fact, all the plants on Earth incorporate symbiotic cyanobacteria (known as chloroplasts) to do their photosynthesis for them down to this day.

9. EVOLUTION OF ATMOSPHERE OXYGEN CONTENT
Slide 4 of 7
EVOLUTION OF ATMOSPHERE OXYGEN CONTENT
Banded iron formation
Continental Redbeds
Billions of years before present
Today
1.0
2.0
3.0
4.0
Cumulative oxygen production
Rise of atmospheric O2
Little atmospheric O2 20 40 60 80
100
Redbeds
Banded Iron formation
At about 2.5 Ga, oceans were saturated with oxygen and free oxygen was added to the atmosphere. Resulting surface oxidation produced first redbeds on the continents
Most of that oxygen was dissolved in the oceans where it combined with iron and precipitated until about 2.5 billion years ago to form iron oxides in banded iron formation

10. Slide 5 of 7
Oxygen began to build up in the atmosphere The Great Oxidation Event, the Great Oxygenation Event,  Oxygen Catastrophe,  Oxygen Crisis,  or Oxygen Revolution

11. Slide 6 of 7
Ultraviolet light split O2 molecules forming ozone (O3) that shielded the surface from intense solar radiation. At that point, life could emerge from the ocean and colonize the continents.

12. Slide 7 of 7
Goal to understand:
Read:
Climate, volcanism, plate tectonics all played a key role in regulating the oxygen level during various time periods.
Yet no one has produced a rock-solid test to determine the precise oxygen content of the atmosphere at any given time from the geologic record.
But one thing is clear—the origins of oxygen in Earth's atmosphere derive from one thing: life.

13. Draw a Picture in the boxes, Write the subtitles,
Story Board
Early Earth Atmosphere
Cyanobacteria and Photosynthesis
Oxygen accumulation
Atmosphere Today
Draw a Picture in the boxes,
Write the subtitles,
Write a detailed sentence for each