Strong Winter Storms can move 600-ton Boulders Around: What Could a Superstorm Do?

A new study has confirmed that waves generated by powerful storms can move massive seaside boulders that weigh hundreds of tons, and as global warming spurs stronger and more powerful storms, this finding illustrates the sheer force that our planet’s weather will challenge us–and the shape of our coastlines–with, in the decades to come.

A research team led by Rónadh Cox, a professor of geosciences at Williams College, recorded the positions of thousands of boulders on the west coast of Ireland in 2013. Following an extraordinarily stormy winter, the team returned in the summer of 2014 to find that 1,153 rocks, ranging in weight from a tenth of a metric ton to more than 500 tons, had been moved by waves generated by the storms, including the dramatic displacement of eighteen Very Large Boulders (VLB)–boulders that weigh over 50 tons. Two of these VLBs, weighing in at 475 ton and 620 ton each, had moved 4 meters (13 feet) and 3.5 meters (11.5 feet) respectively.

To put that in perspective, the 620-ton rock, labeled Boulder 293, weighs more than five times that of a blue whale, or three times that of a Boeing 747–a slab of stone that might’ve made some ancient megalith builders balk. In addition to having moved nearly 12 feet over the span of a year, a 60-ton slab of rock that had been on top of it in 2013 was now missing in 2014. Additionally, the force that had moved the other, 475-ton, rock had rotated it roughly 50º counter-clockwise along its 13-foot journey.

In 2016 climatologist and climate activist Dr. James Hansen published a study warning of the potential for a superstorm-like scenario, including evidence for an ancient tempest that had thrown 1,000-ton boulders to the top of a 20-meter (66-foot) cliff in the Bahamas. At the time, the finding was criticized as being unrealistic, with some critics doubting that ocean waves could be powerful enough to launch an object of that mass that far. But this new finding shows that storms of far more modest power can still push stones up to half the size of Hansen’s megaboulders around, prompting the question: What force would a superstorm scenario be able to throw at us?