Scientists are warning that 2018 won’t be as “easy” on us as 2017 was when it comes to the number of severe earthquakes they predict. In 2018, Earth, and one billion of its inhabitants could face 20 severe earthquakes due to the slowing rotation of the planet.

Tiny changes in the speed of our planet’s rotation will trigger huge seismic activity by releasing vast amounts of underground energy causing severe earthquakes, experts claim. Although their research has been rejected by some scientists, they are intent on sounding the alarm. The slowing of Earth’s rotation could disrupt the crust of the Earth making it possible to see 20 severe earthquakes next year.

According to the Daily Mail, the planet’s rotation is slowing down because of tidal forces between Earth and the moon. The side of Earth closest to the moon feels its pull the strongest, while the side farthest from the moon feels its gravity less. That difference in gravitational pull stretches the Earth, which causes tidal bulges. These bulges pull the moon closer or farther away from Earth by around 4cm per year. The moon exerts the opposite force on them, pulling them back toward it, creating friction and slowing down the planet’s rotation. The time the Earth takes to make a complete rotation on its axis varies by about a millionth of a second per day. While the rotational rate hasn’t declined evenly,  the average day has grown longer by between 15 millionths and 25 millionths of a second every year.

Researchers found five periods in the past century when there were more earthquakes than other times. On these five occasions, there was a 25 to 30 percent increase in the number of earthquakes with a magnitude of 7 or above. These all coincided with a slowing in the rotation of the Earth. Scientists from the University of Colorado in Boulder and the University of Montana say that even fluctuations of a millisecond could increase seismic activity.

The minuscule variations in Earth’s rotation cause a shift in the shape of the Earth’s iron and nickel “inner core.” This, in turn, changes the liquid outer core on which the Earth’s tectonic plates rest. “The mechanism we’ve come up with is that as the Earth slows down it’s like a skater spinning on ice. As the Earth slows down its equatorial diameter reduces,” Dr. Rger Bilham of the University of Colorado told BBC Inside Science. “Its (the Earth’s) waistline gets smaller, but its clothes, the tectonic plates on Earth, remain the same size, which means they get rumpled up. These tiny changes to the overall shape of the Earth are enough, if there are faults that are already ready to go … to kind of kick them over into failure,” he said.

“The correlation between Earth’s rotation and earthquake activity is strong and suggests there is going to be an increase in numbers of intense earthquakes next year,” Dr. Bilham said.

This research comes just after a 7.3-magnitude earthquake struck Iran, leaving at least 400 people killed and more than 6,000 injured. The quake hit 19 miles southwest of Halabja in Iraqi Kurdistan at around 9.20pm on Sunday, when many people would have been at home. More than 100 aftershocks followed.