This Rock Has a Voice And You Can Listen to It

30 Aug

When you're approaching Castleton Tower, a 400-foot-tall rock formation near Moab, Utah, it seems completely quiet. And if you place your hands and feet on the sandstone, it’ll feel perfectly still. 

But, like other large rock formations, Castleton Tower hums. It vibrates from energy produced by earthquakes, ocean waves, cities, trains, and road traffic, or even from wind or aviation noise in the air. 

And thanks to a group of geologists at the University of Utah—and a couple of ambitious rock climbers—now you can hear it. 

The researchers, led by geologist Jeffrey R. Moore, published a study on Tuesday in the Bulletin of the Seismological Society of America that shared a recording of the tower’s vibrations. To make the recording, Moore’s team used seismometers, devices that pick up slight movements in the earth in three dimensions. They then amplified and sped up the nearly three-hour recording to a frequency audible to humans. 

You can listen to the rock here:

“It has ebbs and flows to it, but it’s largely a sort of droning sound, emphasizing how the tower is always vibrating as energy comes up through the earth,” says Paul R. Geimer, PhD, an author on the study. 

Moore and his colleagues have been measuring the vibrations of rock formations since 2013, but had previously been limited to small structures such as arches, bridges, and hoodoos (pinnacle-like structures). In order to listen to a rock, one needs to ascend it, to place a seismometer on top of the structure. So formations like Castleton, which is one of the largest free-standing rock formations in the Southwest, pose a challenge for scientists. 

That’s where Kathryn Vollinger and Natan Richman came in. Both seasoned rock climbers, Vollinger and Richman were looking for ways to keep their skills sharp during the off-season. They found and reached out to Moore’s group in December 2017 with a standing offer to climb larger, more technical rock formations and set up seismometers. The researchers jumped at the chance. “Their skills provided us an opportunity to measure something we couldn’t just walk up to,” says Riley Finnegan, another author on the study. 

After a few weeks of training to get the climbers comfortable with the equipment, they were sent to climb Castleton Tower in March 2018, placing one seismometer at the base for reference and another at the top to measure the movements.

The recording confirmed what the researchers originally thought: that the Tower behaves as “one slab of intact rock, connected from top to bottom,” says Geimer. It vibrates at a very low frequency, likely due to its enormity. Smaller rock formations vibrate at higher frequencies—Finnegan compares this to the strings on a guitar. This makes Castleton less sensitive to accumulating damage over time compared to structures that are more susceptible to transferred energy, according to Finnegan.

Major collapses in Arches National Park, like the one that occurred in 2008, were motivating events for the group's research, says Geimer. “We are trying to identify any precursors in these rock formations before either there is going to be a rockfall or these features are going to fail. It’s a way to non-invasively listen in and assess the health of these features.” 

Castleton Tower was first climbed in 1961 and was named in the 1979 book, Fifty Classic Climbs of North America, earning a place on many climbers’ to-do lists. 

Sharks Swim Near Humans a Lot More than You Think

28 Aug

Last week, a video of people hydrofoiling within feet of great white sharks off Capistrano Beach in Dana Point, California, made the internet rounds.

Even when the hydrofoilers zoom directly over the animals, the sharks don’t seem to care. Since drones became a ubiquitous sight off beaches and piers, amatuer filmmakers have been capturing videos like these and sending them to the media, who, in the words of Chris Lowe, professor of marine biology and director of the Shark Lab at California State University at Long Beach, “gobble them up.” People tend to get a bit freaked out when they realize how close we can unwittingly come to some of nature’s most refined predators.  

The Shark Lab has started to use drone footage to study why sharks, often baby or pregnant ones, tend to hang out in shallow waters as well as how they behave when they encounter humans. 

“We have a lot of footage and anecdotal evidence of sharks swimming around where humans play, and as long as people aren’t harassing them, the sharks just don’t care,” says Lowe. 

And often “the surfers don’t even notice,” he says. For example, pro surfer Kelly Slater didn’t seem to be aware of a shark that photobombed his GoPro footage in 2014. 

Lowe hopes to have data on sharks’ attitudes toward close-proximity humans in a couple of years. For now, “when there are a lot of people and sharks in shallow water together, most of the time nothing happens,” he says. However, swimming in groups and avoiding the water at dawn and dusk can reduce your risk of encountering sharks, friendly or not. 

In withdrawal after the end of Shark Week 2019? Here’s even more drone footage:

Sharks Approach Surfers 

Sharks Circle Surfers in South Africa

Tiger Shark Passes by Swimmers in Miami

Sharks and Surfers Within Feet of Each Other

Surfer Falls onto a Shark

Unraveling the Mystery of the Himalayas’ Skeleton Lake

21 Aug

In a thousand-year-old Himalayan folk tale, a king and queen, followed by their attendants, trek into the mountains of northern India to the shrine of Nanda Devi, the mountain goddess. But on the way, the goddess strikes the pilgrims down for their celebratory and inappropriate behavior, and they fall into small, glacial Roopkund Lake. 

In 1942, a British forest ranger assigned to patrol the Indian Himalayas during the Second World War came across the lake and found the skeletal remains of hundreds of people. News spread, and Roopkund Lake, in the present-day Indian state Uttarakhand, was rechristened Skeleton Lake. 

Thus began a now 77-year-old mystery about who these humans were, what brought them to the isolated, often frozen lake, and how they died.

The Nanda Devi tale could help explain the bodies. The pilgrimage they attempted, the Nanda Devi Raj Jat, is a three-week journey still undertaken today to worship the goddess. Some hypothesize that the bodies could be evidence of a fatal 19th-century military expedition, but when many women’s bodies were found in the lake, this idea fell out of favor. Based on evidence of compression fractures on a few of the humans’ skulls, the most common belief is that a hailstorm killed them all at once sometime between 830 and 850 A.D. A new study published Tuesday in Nature Communications, however, contradicts this theory. 

In the study, researchers radiocarbon-dated and genetically analyzed the skeletal remains of 38 bodies found in the lake to find out how old the bones are and the individuals’ ancestry. They also analyzed the stable isotopes in the samples to learn more about what they ate. What the researchers found surprised them. 

“The assumption was that all the skeletons dated to around the eighth century, but it became clear that this is not what happened,” says Éadaoin Harney, the lead author of the paper and a doctoral candidate at Harvard University’s department of organismic and evolutionary biology. The bodies in the lake, instead of dying in a single catastrophic event, range from a few hundred to a thousand years old. 

The authors also assumed that the individuals were all from the Indian subcontinent, as this is what previous studies had thought. But once they had the ancient DNA samples, “it was clear this was definitely not the case,” says Harney. 

Genetically, the remains fall into three distinct groups, ranging from 1,000-year-old populations from South Asia to 200-year-old populations from Greece and Crete, along with one individual from East Asia. Twenty-three of the bodies analyzed were from South Asia, whereas 14 were of Mediterranean origins. Even those individuals from South Asia “have ancestry that’s really diverse,” says Harney. “It’s not a single population coming from somewhere within India. Instead it’s people from all over the subcontinent.”  

The results of the isotope analysis also show diverse diets within and among each subgroup, adding to the mystery. 

As for how they died there and why, Harney says: “The only hint that we have is that Roopkund Lake is located along the pilgrimage route that may have been used for the last 1,000 years.” And yet, for Harney, it is difficult to imagine this as the sole reason for such a genetically and culturally diverse set of people to die in the same remote lake. 

“We’re still pretty puzzled,” she says, and more research is needed to determine the exact nature of these deaths. A massive hailstorm still can’t be ruled out, but the scientists wonder if the hailstorm was the fatal blow or if it occured after the people died.

And compared to other archeological sites, Roopkund is challenging to study. “It’s been subject to so much disturbance, both from the natural environment, like rockslides,” says Harney, and from hikers on the nearby trail going down to retrieve bones or look at the site. 

The study does highlight the ways in which humans have traveled to far-off places for hundreds, if not thousands, of years. “We knew that there were long-distance connections,” says Harney, but the new knowledge demonstrates “how important migration and connections between different parts of the world have been throughout history.”

Will Climate Change Close the Matterhorn?

9 Aug

Should the Matterhorn close? That question arose again last week after at least one anonymous guide told the Swiss newspaper Tages Anzeiger that the mountain was too unstable and therefore too dangerous to climb. 

The comment came after a South Korean climber and his guide died last month after a rock fell and damaged a fixed rope on the east flank of the mountain. A total of six people have died on the Matterhorn so far this year, and 11 died attempting to reach its summit last season. The 14,642-foot peak has always been one of the world’s most dangerous; it’s estimated that more than 500 people have died since it was first summited in 1865. 

“The Matterhorn is not a piece of solid granite. It’s a piece of shales [soft, stratified sedimentary rock]. It’s not very stable,” says Raphael Mayoraz, a geologist, mountain guide, and head of the natural-hazards department of the Swiss canton of Valais, where the mountain is located. A study by the PermaSense project released in 2019 found that melting permafrost and receding glaciers have made rockfalls an even greater danger on hot summer days.

Mayoraz says he’s noticed changes in the Alps since his early days as a mountain guide. The north faces of the range used to be perpetually covered in snow, meaning climbs were on hard, packed snow and ice. But much of that “has been melting, which means now most north faces are pure rock, and they are less stable,” he says. 

In winter, snow fills the gaps between loose, unstable rock on the upper layers of the Alps. That snow turns to ice at freezing altitudes, which acts as a glue, keeping the rocks in place. A colder, snowier winter will create more ice, while extremely hot summers like those in recent years melt it, causing an increased risk of rockfall. Because of this phenomenon, the north face of the Matterhorn has become almost too dangerous to climb in the summer, according to Mayoraz. This includes Hörnligrat Ridge, on the northeast face, the most popular route to the summit.

Rockfall happens, says Jonathon Spitzer, director of field operations at Alpine Ascents International, who monitors the conditions on the Matterhorn daily. “It’s more prevalent in the Alps than anywhere else in the world that we guide, just because the permafrost there is melting drastically with climate change,” Spitzer explains. 

The mountain closed for several days in 2003 after a major heat wave resulted in 35,000 cubic feet of rock sliding off the Hörnligrat Ridge, forcing the evacuation of 90 climbers. This led scientists from the PermaSense project to install wireless sensors where the rockfall occurred.

But the notion that the Matterhorn should close now doesn’t make sense, according to Mayoraz. It would be impossible to keep climbers off it anyway. “It’s a big mountain. There are probably 20 routes that go to the top of Matterhorn, or even more, so what are you going to do?” 

“Glaciers are receding very quickly,” says Mayoraz. Two-thirds of the glaciers in the Alps will be lost by 2100, according to a study published in the geosciences journal ​​​​​​The Cryosphere in April. “There are new crevasses. You need to find new routes to go on the glacier. It’s a continued adaptation, but that’s part of alpinism: finding the best way, the safest way.”

There are no plans to close the Matterhorn this year. “No one, and even less the mountain guides, are in favor of a closure,” says Pierre Mathey. managing director of the Swiss Mountain Guide Association. And Alpine Ascents has no plans to halt its guided trips, says Spitzer. It has four more groups attempting the summit this year. “We tell them up front that we need to be aware that rockfall is prevalent,” says Spitzer. 

Mayoraz says that people climb the mountain at their own risk. Whether to ascend a mountain is a decision, he believes, that local authorities should have no role in making for individual climbers. “Where is the limit? When do you open and when do you close a, by the way, pretty shaky mountain?”