An increase in the number of devastating earthquakes around the world is being predicted for 2018, according to the University of Colorado’s Roger Bilham and Rebecca Bendick of the University of Montana. The two geologists have made a detailed study on earthquake activity recorded since 1900, and found that increases in the number of major earthquakes tend to follow predictable cycles, and 2018 happens to fall in one of those years.

Bilham and Bendick’s study found five specific periods of time, occurring at 32-year intervals, when the number of major earthquakes would increase to between 25 and 30 events per year, nearly double the 15 major earthquakes that would be seen normally. Searching for a correlation, they found that the increases corresponded to an even bigger — albeit more subtle — event: periods when the Earth’s rotation slows by a (comparatively) significant amount.

Earth’s rotation is gradually slowing, with the emphasis on gradually: today’s day is now 1.7 milliseconds longer than it was a century ago, and if you thought there wasn’t enough hours in the day as it is, 600 million years ago there was only 21 hours in the diem to carpe. This long-term slowing is attributed to the affect the Moon’s gravity has on the planet, although other factors, such as ocean and ice volume on the Earth’s surface, plus a host of other unknown factors, can also cause subtle changes in our planet’s spin.

Bilham and Bendick found that each of these five earthquake-heavy periods were preceded by the peak of a decades-long slowdown in the Earth’s rotation, when the length of a day would be several milliseconds longer than it had been years before. Earth’s crust rotates at a slightly different speed (and on a different axis) than the planet’s core, so subtle changes in the difference in these speeds appear to translate into major shocks for us itty-bitty humans on the surface.

As for 2018 itself, Earth entered one of these slowdown periods more than four years ago, so if the pattern holds, we might be in for a bumpy ride. “The inference is clear. Next year we should see a significant increase in numbers of severe earthquakes. We have had it easy this year," explains Bilham, referring to 2017’s earthquake activity. "So far we have only had about six severe earthquakes. We could easily have 20 a year starting in 2018."