Storm Surge Carries Huge Boulders
A typhoon carried 180-ton rocks 150 feet up a beach—the largest transport recorded in recent times.
Watch the video clip in a story on Live Science titled “Super Typhoon Shoved Car-Size Boulders Onto Philippine Beaches.” The scene is pretty scary. Waves destroy a house in seconds in an eyewitness video of the “super typhoon” Haiyan that struck the Philippines in November, 2013. With sustained winds of 195 mph and powerful surges of sea water, the storm carried limestone boulders the size of stretch limos as far as 600 feet inland, and 30 feet uphill. One 30-foot stone estimated weighing 180 tons was carried along the beach 150 feet.
“If we didn’t know this occurred from a typhoon, people would have started drawing tsunami maps,” said Andrew Kennedy, a coastal engineer at the University of Notre Dame in Indiana who counted hundreds of boulders during a damage survey soon after Haiyan hit. “There are so many, and they went so far.“
How could a common typhoon have the power of a tsunami? A mechanism identified in the 1950s was apparently responsible: infragravity waves.
Robert Weiss, a coastal scientist at Virginia Tech in Blacksburg, modeled Haiyan’s waves and storm surge, concluding that rare, tsunami-like waves called infragravity waves were responsible for scattering the huge boulders like they were seashells. This kind of wave forms when ordinary wave sets — the groupings coveted by surfers — merge into one large, long-period wave at steep drop-offs close to shore.
This will make it difficult for investigators of prehistoric storm damage to distinguish between the two mechanisms, but it also underscores the tremendous power of moving water.
Another example of rapid change from moving water can be seen today in the northwest US. CMI posted an article from 2002 by John Morris, geologist with ICR, about a canyon near Walla Walla, Washington that formed in six days. Initially 10 feet deep and 6 feet wide, it grew to 1,500 feet long, 120 feet deep and 120 feet wide when water was diverted into it back in 1926. Five million cubic feet of material were removed in less than a week.
The eruption of Mt. St. Helens also showed the power of fluid motion. A mudflow in 1982 carved a “miniature Grand Canyon” at 1/40th scale through sediments laid down by the initial 1980 eruption (see ICR article). These canyons were observed to form in a matter of hours or days, but it’s also probable that other canyons were formed rapidly before observers were present. It is now thought that Yellowstone’s Grand Canyon, for example, was carved quickly by water that breached ice dams, then eroded through rock weakened by hydrothermal activity (Yellowstone.net).
On Mars, the major canyon system Valles Marineris is long enough to stretch across the United States. Arizona’s Grand Canyon would fit in one of its tributaries. Just this week, geologists presented evidence that it was carved by glaciers. According to Space.com, researchers using data from the Mars Reconnaissance Orbiter suggested the glacial origin due to high concentrations of jarosite, a rock that only forms on Earth in very acidic water. “Getting an evaporating pool of water halfway up a 3-mile-high cliff is tricky, and the more we looked into the geologic context surrounding the deposit, the less likely a liquid water origin seemed,” one geologist said. Remote sensing also detected evidence of opal in the canyon walls.
These stories indicate that changes can happen quickly under the right conditions. “Mr. Slow-and-Gradual” Charles Lyell did not know about infragravity waves. Catastrophism became much more widely accepted a century after him, but his doctrine of millions of years of gradualism continues to infect popular thinking. It also played a major role in Charles Darwin’s views of evolution.
Arizona’s Grand Canyon is often still portrayed as a result of slow-and-gradual deposition of sediments. The Tapeats Sandstone, though—the bottom layer of sediments above the Great Unconformity—is littered with house-size boulders. The observational experience with Typhoon Haiyan should indicate the amount of flood surge power required to transport these boulders; it sure wasn’t some spring shower. There are also major folds in the Tapeats, some of them continuing up into other formations above. One fold at Carbon Canyon upturned the sandstone 90 degrees. These folds must have occurred rapidly when the sediments were still soft, because there is no sign of cracking.
What will it take to get science out of the rut dug by Charles Lyell? Reinforcement by the media and simplistic interpretive programs have deepened that rut into a canyon that’s hard to get out of. But we should, to get a better overview of the landscape.