Oxygen collapses again
After the great surge, atmospheric oxygen falls back and stays low for a billion years.
- When
- Known to
- ± 50 million years
- Era
- Paleoproterozoic, Proterozoic
The end of the Lomagundi excursion around 2.06 billion years ago is followed by a sharp decline in oxygen. Levels settle far below modern values — possibly a few percent — and remain there for well over a billion years. Deep oceans stay anoxic and in places sulfidic. This long, low plateau is the setting for what has been called the Boring Billion, and it is probably why complex life took so long to appear.