Photographic Evidence: Boulders Show Impact of Superstorms

January 26, 2018

One of the controversial aspects of James Hansen’s most recent paper on climate change and superstorms has been that a lot of people just don’t believe one of the key assertions, that giant boulders in the Caribbean show indications of having been moved up to cliff tops by giant storm waves, in previous warmer climates.
Now new evidence to establish that might be true.

Earther:

On the rocky shores of a windswept island just west of Ireland, the 620-ton boulder looks almost at home. But careful analysis of its position over the last few years has revealed something odd: between the summers of 2013 and 2014, the boulder shifted a couple meters toward the sea. That discovery is causing scientists to rethink what they know about the impacts of powerful storms.

In fact, the rock is one of more than a thousand boulders—including a handful of Very Large Boulders (VLBs and yes, that’s a technical term) weighing over 50 metric tons—shuffled around by the powerful storms that pounded Ireland’s west coast during the winter of 2013-2014, the stormiest in decades. Described in a new paper in the journal Earth Science Reviews, these boulders offer some of the first concrete evidence that storm waves, not just tsunami waves, can pack enough punch to hurl giant chunks of Earth around. (For comparison, 100 metric tons is about half the weight of a Boeing 747.)

In a warming world where more energy in the oceans and atmosphere could mean more powerful storms, that’s an important insight.

“Ten years ago, it was possible to say storms can’t move 50 ton boulders,” lead study author Rónadh Cox, a professor of geosciences at Williams College, told Earther. “If you were building a model of storm intensity or thinking about risks posed by severe storms, then your upper level for storm energy were to some extent informed by that understanding.”

“What our work is showing is in fact yes, storm waves can be tremendously strong,” she continued.

vlb

In total, the team cataloged 1153 boulders that had been displaced the previous winter, ranging in size from a tenth of a metric ton to more than 500. Eighteen of the boulders were VLBs, while six of these Large Boys exceeded 100 metric tons in weight. The biggest? A 475-ton and a 620-ton boulder, both located on the island of Inishmore.

Boulders weighing hundreds of tons were generally restricted to a few meters of movement, and tended to huddle around the shoreline. Smaller boulders, however, could be transported further, and some were seen at up to 222 meters (730 feet) inland, and nearly 30 meters (100 feet) uphill.

Taken together, the authors write, these findings show that yep, storm waves can move massive rocks. That’s an important insight for a few reasons.

For one, it tells us something about total potential power of storm-generated waves. That has obvious implications for forecasters and urban planners hoping to minimize the impact of storms on coastal infrastructure today.

Secondly, we live on a warming planet, and one of the expected consequences of climate change is more intense storms that can dump more water and pack fiercer winds. Understanding fully the impacts of the most powerful storms will only become more relevant as we prepare for the future—and try to mitigate the worst effects of climate change.

Adam Switzer, a coastal hazards researcher at the Earth Observatory of Singapore who was not involved with the research, praised the new study for containing “a very detailed review and a great dataset that will now allow engineers and modellers new insights into offshore wave power and rocky shoreline dynamics.”

“We know that storm waves are capable of moving very large boulders but when it comes to individual storms we have very little data on how many, how far, and how they move?” he said. “This study really adds a great body of evidence to what storm waves can do at the coast.”

Robert Weiss, a coastal hazards researcher at Virginia Tech who also wasn’t involved, called the study’s dataset “impressive” adding that “it will give us work for the next decade.”

“The way the data was collected should serve as role model for studying the impacts of storms in the future,” Weiss said.

 

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3 Responses to “Photographic Evidence: Boulders Show Impact of Superstorms”

  1. Sir Charles Says:

    Here the video abstract:

  2. indy222 Says:

    In my own public talk on Hansen’s work, I showed how Tsunami’s generated in the typical way, by subduction zone earthquakes, cannot explain those Bermuda boulders, based on the placement of subduction zones. I also show that the other idea put to me, that perhaps like in that old Nova program where a volcanic subsea collapse might tsunami the U.S. East Coast, has no support in the historical record for the Canary Islands, which instead of many much smaller slides. The argument for superstorm-carried boulders is strong.

  3. indy222 Says:

    “….instead HAVE many much smaller slides” I meant to say above.


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