Over the past 260 million years, dinosaurs have appeared and disappeared on Earth, the supercontinent Pangaea has split into continents and islands, and humans have changed the world rapidly and irreversibly.
Even so, Earth seems to have its own timeline. A new study of ancient geological events suggests that the planet has a slow, steady “heartbeat” of geological activity every 27 million years or so.
The pulse of grouped geologic events includes volcanic activity, mass extinctions, tectonic plate realignments and sea level rise. Scientists believe the next such destructive cycle is another 20 million years away.
“Many people believe that geological events are random in time. But our study provides statistical evidence for a particular cycle, suggesting that these geologic events are correlated, not random,” says study author Michael Rampino, a geologist at New York University.
He and his team conducted a new analysis of 89 well-studied geological events over the past 260 million years. From the analysis, it became clear that some of the time segments were really severe-more than eight devastating events occurred in geologically short time intervals.
“These events include times of marine and nonmarine extinctions, major oceanic cataclysms, continental eruptions of flood basalts, sea-level fluctuations, global pulses of intraplate magmatism, and seafloor changes and plate reorganization,” the scientists say.
“Our results show that global geologic events tend to correlate and seem to occur on a cycle of about 27.5 million years,” the team adds.
Geologists have long studied the potential cycle of geologic events. Back in the 1920s and ’30s, scientists assumed that the geological record had a cycle of 30 million years; later the time was reduced to 26.2 million years.
Now scientists believe that pulses occur every 27.5 million years. The study shows that the 27.5 million year mark is the time of the mass extinction on Earth.
Researchers do not yet know exactly what causes such a “heartbeat” of the Earth. Some suggest that it is the impact of comets, while others blame the so-called Ninth Planet.