Every interval page on this site quotes these three for its own slice of time. Put them together and the argument stops needing words: oxygen crosses the line you can stay conscious above at roughly 550 Ma, and does not reach the line fire needs until roughly 420 Ma. The gap between those two numbers is why the middle of this site reads the way it does.
Three panels rather than one, because these quantities share no common scale and stacking them on a single axis would invent a relationship that is not in the data. They share the time axis only.
Hover anywhere on the chart to read all three at that moment, or focus it and use ← → (hold shift to move faster). The axis has a deliberate break at 539 Ma: on a straight linear scale the whole Phanerozoic, which is every interval you could last more than a few minutes in, is squeezed into the last 12% of the width.
| Interval | Starts | Oxygen | CO₂ | Mean temp | You last |
|---|
The top panel carries two rules. The lower, near 10%, is where a human stops staying conscious, and the curve spends four billion years underneath it. The upper, near 16%, is where fire starts to burn. They are crossed 130 million years apart, and treating them as one number, which this site did until recently, hides the more interesting half of the story.
Oxygen peaks near 35% around 305 Ma while CO₂ simultaneously bottoms out near modern values. Both are the same event: forests burying carbon faster than anything could rot it, which is the coal.
Oxygen collapses from 35% to about 15% while temperature spikes 10 °C. The two worst post-Cambrian survival verdicts on this site sit precisely in that trough.
Four deep negative spikes: the Huronian, the two Snowball Earths, and the Hirnantian glaciation. Two sharp positive ones: the end-Permian at 252 Ma and the PETM at 56 Ma.