What does the deep-time record reveal about how the Earth system behaves?

Why the question matters

Deep time supplies the only observations of the Earth system responding to perturbations far larger than anything in the instrumental record. Which feedbacks proved strong enough to matter then is evidence about which ones matter now.

It also shows that the buffering capacity of the carbon cycle has changed over Earth history, as organisms evolved that altered it. Stability is a product of the biosphere's current configuration rather than a fixed property of the planet.

Claims of periodicity in the geologic record are notoriously easy to generate and hard to substantiate, which makes propagating dating errors through the analysis, and testing for the same signal in independent records, the substance of the work.

What our research finds

• Twenty-eight of the 47 chronostratigraphic stage boundaries of the last 253 million years coincide with a stratigraphic sequence boundary, and both records independently carry the same 31-million-year cycle at better than 99.9 per cent confidence (Rampino and Caldeira, 2025).
• All six major marine mass extinctions of the past 541 million years coincide with dated continental flood basalt eruptions, as do six minor ones, each marked by stratigraphic mercury anomalies confirming the synchrony (Rampino et al., 2024).
• Ocean anoxic events, marine extinctions and flood basalt eruptions of the last 260 million years share underlying cycles of about 32.5 and 26.2 million years, with 13 of 17 anoxic intervals carrying mercury anomalies marking contemporaneous volcanism (Rampino et al., 2023).
• Non-marine tetrapod extinctions show a 27.5-million-year periodicity at 99 per cent confidence, matching the marine record, and all eight coeval pulses coincide with Large Igneous Province eruptions (Rampino et al., 2021).
• A revised set of 37 dated impact craters yields a 25.8-million-year cycle and the eight marine extinctions of the same interval a 27.0-million-year cycle at a similar phase, with neither result resting on the Chicxulub impact and the end-Cretaceous extinction (Rampino and Caldeira, 2015).
• C3 plant productivity, root biomass, and canopy transpiration all collapse as atmospheric carbon dioxide falls below about 200 parts per million, shutting down the biological amplification of silicate-rock weathering; adding a critical threshold of 150 to 250 parts per million reproduces the observed floor in atmospheric carbon dioxide over the past 24 million years (Pagani et al., 2009).
• Producing more than 5 degrees Celsius of Paleocene-Eocene warming requires a total carbon release of roughly 5,400 to 112,000 petagrams — against about 5,000 petagrams in conventional fossil fuel resources today — unless climate sensitivity was far higher than the usual 1.5 to 4.5 degrees Celsius per doubling (Pagani et al., 2006).
• A collapse of marine primary productivity reproduces the abrupt end-Permian carbon-isotope excursion and drives atmospheric CO2 from a Late Permian 850 ppm to about 2,500 ppm (Rampino and Caldeira, 2005).
• The evolution of planktic calcifiers introduced saturation-dependent carbonate preservation on the sea floor, stabilising the climate system and explaining why Neoproterozoic-style near-global ice ages have not recurred (Ridgwell et al., 2003).
• Silicate-mineral dissolution is nearly independent of pH between 5 and 8 and the deep ocean sits above 7.5, so low-temperature seafloor basalt alteration cannot act as an effective feedback on atmospheric CO2 — weathering on land does (Caldeira, 1995).
• Major geologic events of the past 250 million years show a statistically significant periodic component of 26.6 million years, robust at around 30 million years once dating errors are allowed for (Rampino and Caldeira, 1993).
• Atmospheric CO2 adjusts over more than 100,000 years while sea ice and snow adjust in under a year, so the silicate-weathering thermostat cannot stabilize the ice line against a rapid perturbation, and CO2 clouds could have made an early global glaciation irreversible (Caldeira and Kasting, 1992).
• Because C4 photosynthesis can persist at atmospheric CO2 below 10 parts per million, a C4-plant-based biosphere could survive at least another 0.9 to 1.5 billion years rather than the roughly 100 million years implied by a C3 limit (Caldeira and Kasting, 1992).
• Sustained enhancement of chemical weathering in the late Cenozoic requires an increased flux of CO2 to the atmosphere, and the shift since the Jurassic from primarily cratonic to primarily pelagic carbonate accumulation supplies one, because sea-floor spreading carries pelagic carbonate into subduction zones where metamorphism returns its carbon to the atmosphere (Caldeira, 1992).
• A carbonate-silicate cycle model gives mid-Cretaceous atmospheric CO2 of 3.7 to 14.7 times the pre-industrial value of 285 ppm from super-plume tectonics, implying 2.8 to 7.7 degrees Celsius of warming, though CO2 released from oceanic plateaus alone is unlikely to account for more than 20% of that increase (Caldeira and Rampino, 1991).
• Partitioning carbonate burial between shallow-water and deep-water settings gives two stable steady states — a continental mode with low metamorphic CO2 flux and a pelagic mode with high flux — and Cenozoic burial patterns suggest the Earth is moving from the continental toward the pelagic mode over roughly 100 million years (Caldeira, 1991).