ATMOSPHERE × EARTH

The Oxygen That Went Away

~2.06 to 1.95 billion years ago

Proterozoic · Paleoproterozoic · Rhyacian

The great burst of oxygen that followed the first oxygenation did not last: oxygen sank back to a fraction of its peak and stayed there for more than a billion years, the stretch known as the boring billion. The best-supported culprit is phosphorus, the nutrient no photosynthesiser can do without. When its supply ran short, less organic carbon got made and buried, and it is the burial of carbon that lets oxygen pile up in the air.

Why it matters

Oxygen did not climb smoothly to today's level. It overshot, collapsed, and then barely moved for a thousand million years.

Dating & uncertainty

Carbon isotopes return to baseline, marine sulfate evaporites and phosphorites stop forming, and shales become less oxidised. The favoured explanation is that the phosphorus supply that had driven the burst ran out; a rival account ties the whole episode to a change in volcanic carbon degassing.

Sources

1. Bekker & Holland (2012), Earth and Planetary Science Letters · Oxygen overshoot and recovery during the early Paleoproterozoic
2. Eguchi et al. (2019), Nature Geoscience · Great Oxidation and Lomagundi events linked by deep cycling and enhanced degassing of carbon
3. Hodgskiss & Sperling (2023), Annual Review of Earth and Planetary Sciences · Deconstructing the Lomagundi-Jatuli carbon isotope excursion

Earth history as one day

13:06:3610 h 53 min before midnight

if Earth’s 4.54 billion years were compressed into a single day