Guest eye-rolling by David Middleton
From the alarmists who brought you, “Climate Change Is Causing the Seafloor to Sink“…
Apparently Storms Can Push 600-Ton Boulders Around
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.”
“Ten years ago, it was possible to say storms can’t move 50 ton boulders”… This is where I rolled my eyes.
But, 20 years ago, it was possible to say that storms did move VLB’s (Ms. Stone is correct about VLB’s being a genuine technical term)…
QUATERNARY RESEARCH 48, 326–338 (1997)
ARTICLE NO. QR971926
Boulder Deposits from Large Waves during the Last Interglaciation on North Eleuthera Island, Bahamas
Paul J. Hearty
The greatest weight (from an estimated denasity of 2.4 g/cm3) is about 2,300 tons for Boulder 1.
OK… The largest Eemian Bahama Boulder was 2,300 tons. It was ten times the size of Holocene boulders moved by waves. That would be 230 tons. Yet, 10 years ago, storms couldn’t move 50 ton boulders.
For that matter, the Irish boulders which couldn’t be moved by storms 10 years ago, were very likely deposited by storms…
PUBLIC RELEASE: 27-NOV-2017
Boulder deposition by tsunamis and storms
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES
A study explores the origin of boulders deposited on cliffs in western Ireland and New Zealand’s North Island. The question of whether tsunamis or storm waves are responsible for the presence of boulders on ocean cliffs remains unsettled. John Dewey and Paul Ryan compared two deposits of boulders weighing more than 30 tonnes on the coastline of Annagh Head, western Ireland and on the Matheson Formation, a Miocene deposit in New Zealand. Oceanographic data, field measurements, and historic storm accounts indicated that Annagh Head deposits, which weigh more than 50 tonnes, are subject to 20-30-meter-high storm waves. Field measurements of the Matheson Formation indicated that a 12-13-meter tsunami with a period of approximately 1 hour could have deposited the boulders, some of which weigh more than 140 tonnes. Further, compared with the Annagh Head deposits, the Matheson Formation deposits are spread over a large geographic region and include a large proportion of ocean floor sediments–both of which are indicative of a tsunami. A numerical model of storm waves indicated that boulder size, shape, and density determine the site at which waves deposit boulders. According to the authors, the Matheson Formation likely represents the deposition of a single tsunami over 1 hour, whereas the Annagh Head deposits likely represent the result of centuries of storms.
Article #17-13233: “Storm, rogue wave, or tsunami origin for megaclast deposits in western Ireland and North Island, New Zealand?,” by John F. Dewey and Paul D. Ryan.
The featured image is a USGS picture of a boulder from a debris flow in Venezuela. I chose not to use the photos from the Earther article to avoid any copyright issues.
via Watts Up With That?
January 25, 2018 at 01:28PM