Volcanic eruptions have long been considered the chief suspect behind Earth’s ancient mass-extinction events. Now, an interdisciplinary team at Florida State University has identified an accomplice that doesn’t require a single eruption at all: metamorphic rocks quietly releasing sulfur and carbon gases as they’re heated deep underground.
Assistant professor of meteorology Michael Diamond, assistant professor of geology Emily Stewart, and geology doctoral student Lindsi Allman combined deep-earth geochemistry with atmospheric science to show that these emissions affect the environment in ways strikingly similar to volcanic eruptions.
“Evidence shows that the process that wipes out species is a climate swing, or an oscillation back and forth between hot and cold climates… As long as geology as a field has existed, scientists have believed that volcanic eruptions and their emissions were the primary trigger for rapid global cooling and climate swings. We found another process that contributes to these events: metamorphism.”
Emily Stewart, Florida State University
How Rocks Can Cool — and Then Warm — the Planet
Metamorphism occurs when rock beneath Earth’s surface is exposed to extreme heat, such as when magma heats rock in a large igneous province like Antarctica’s Ferrar province or Russia’s Siberian Traps. If that rock contains sulfur and carbon, the heating drives those elements out as gases that seep up to ground level.
Sulfur emissions form sulfate particles that act like tiny mirrors in the atmosphere, reflecting solar energy back into space and seeding clouds that reflect even more sunlight — producing sharp cooling spikes. Carbon, released at the same time, behaves very differently.
“Cooling spikes are the result of sulfur, which doesn’t stay in the atmosphere for more than a few days before dissipating. The opposite warming effect is due to carbon… Carbon remains in the atmosphere for hundreds, thousands or even millions of years. Even after sulfate-driven cooling spikes, the atmosphere is several degrees warmer than before due to carbon gas continually warming while sulfur aerosols cool and eventually disappear from the system.”
Michael Diamond, Florida State University
The researchers point to several ancient extinctions that may have been influenced by these emissions: the end of the Ordovician Period roughly 440 million years ago, when up to 85 percent of shallow marine species died; the end of the Devonian Period around 370 million years ago, which killed off reef-building corals and armored fish like Dunkleosteus; the end-Permian “Great Dying” about 252 million years ago, which wiped out up to 96 percent of marine species; and the end-Triassic extinction roughly 201 million years ago, which cleared the way for the rise of the dinosaurs.
Why It Matters Today
Though these events occurred millions of years ago, they serve as natural experiments for understanding how the solid Earth, atmosphere, oceans, and biosphere interact — and how sensitive those systems are to large-scale environmental change.
“Earth’s systems are deeply interconnected, and major environmental changes rarely result from a single isolated process. Scientific progress often comes from integrating geological observations, geochemical evidence, climate perspectives, and biological implications into a unified framework.”
Mike Stukel, chair, FSU Department of Earth, Ocean, and Atmospheric Science
The work was funded by the American Chemical Society Petroleum Research Fund and several programs within NOAA’s Climate Program Office.
The study, “Metamorphic sulfur release as a driver of sustained cooling and mass extinction,” was published July 8, 2026, in Science Advances (DOI: 10.1126/sciadv.aee2277).