Hear the First Recording of Volcanic Thunder

Cyrus Read, Alaska Volcano Observatory/U.S. Geological Survey
Cyrus Read, Alaska Volcano Observatory/U.S. Geological Survey

Researchers at the Alaska Volcano Observatory in Anchorage have managed to record the sound of volcanic thunder for the first time, Smithsonian magazine and The Guardian report. It's extremely difficult to differentiate the sound of thunder from the sounds of the eruption itself, which has made conclusively identifying the sonic phenomenon on tape impossible until now.

"It's something that people who've been at eruptions have certainly seen and heard before, but this is the first time we've definitively caught it and identified it in scientific data," Alaska Volcano Observatory seismologist Matt Haney explained in a press release. He and his colleagues published their observations in the journal Geophysical Research Letters.

Using a microphone array almost 40 miles away, Haney's team picked up the sounds of volcanic thunder in March and June 2017 in the midst of two explosive eruptions of the Bogoslof volcano, a mostly submarine volcano in Alaska's Aleutian Islands. (Only about 300 feet of the approximately 6000-foot-tall volcano is above sea level.) The eruptions resulted in huge plumes of ash, a prime environment for volcanic lightning to occur. The volcano continued to generate ash plumes long after the eruptions ended, so the researchers could compare the post-eruption lightning with the timing and volume of the sounds they picked up on the microphones, and positively identified the volcanic thunder. They found that the intensity of the lightning was about the same as the intensity of the thunder's noise.

The technique could allow scientists to study volcanic lightning more easily by using the sound of thunder as an approximation, which may indicate how big the ash plume could grow. That information could reveal dangers for nearby aircraft.

You can hear the thunder for yourself in the audio tracks below. The recordings are sped up, and the thunder sounds clicks and pops. The whirring sounds in the first recording are the eruptions themselves.

[h/t Smithsonian]

Lítla Dímun: The Smallest of the Faroe Islands Has Its Very Own Cloud

While some islands are known for their unusual geography or unique history, Lítla Dímun is notable for its weather. The island, which is the smallest of Denmark's Faroe Islands chain, is often capped by a lens-shaped cloud, making it resemble a scene from a fairytale.

According to Mental Floss's own Kerry Wolfe writing for Atlas Obscura, the cloud floating above Lítla Dímun is a lenticular cloud. This type of cloud forms when moist air flows over a protruding geological feature, like a mountain top. When the wind moving up the landmass hits the air current directly above it, a sort of wave is created on the downwind side of the mountain. The moist air falling down this wave evaporates and then condenses into a large, flying-saucer-shaped cloud atop the mountain peak as a result.

Another factor that makes Lítla Dímun distinct is that it's the only one of the 18 main Faroe Islands without human inhabitants. Visitors to the mystical location will instead find a thriving population of sheep. Originally, Lítla Dímun was home to a group of feral sheep likely dating back to the Neolithic era. But they were hunted to extinction in the 19th century. Domesticated sheep were introduced there around the same time, and today, farmers visit the island once a year to round up their flocks.

One of the few signs of human life are the ropes farmers use to scale the cliff faces bordering the island. Even if you have rock-climbing skills, Lítla Dímun may be dangerous to visit. A boat ride to the rocky shore is only possible when the surrounding sea is calm.

[h/t Atlas Obscura]

Why Are Sloths So Slow?

Sloths have little problem holding still for nature photographers.
Sloths have little problem holding still for nature photographers.
Geoview/iStock via Getty Images

When it comes to physical activity, few animals have as maligned a reputation as the sloth. The six sloth species, which call Brazil and Panama home, move with no urgency, having seemingly adapted to an existence that allows for a life lived in slow motion. But what makes sloths so sedate? And what horrible, poop-related price must they pay in order to maintain life in the slow lane?

According to HowStuffWorks, the sloth’s limited movements are primarily the result of their diet. Residing mainly in the canopy vines of Central and South American forests, sloths dine out on leaves, fruits, and buds. With virtually no fat or protein, sloths conserve energy by taking a leisurely approach to life. On average, a sloth will climb or travel roughly 125 feet per day. On land, it takes them roughly one minute to move just one foot.

A sloth’s digestive system matches their locomotion. After munching leaves using their lips—they have no incisors—it can take up to a month for their meals to be fully digested. And a sloth's metabolic rate is 40 to 45 percent slower than most mammals' to help compensate for their low caloric intake. With so little fuel to burn, a sloth makes the most of it.

Deliberate movement shouldn’t be confused for weakness, however. Sloths can hang from branches for hours, showing off some impressive stamina. And because they spend most of their time high up in trees, they have no need for rapid movement to evade predators.

There is, however, one major downside to the sloth's leisurely lifestyle. Owing to their meager diet, they typically only have to poop once per week. Like going in a public bathroom, this can be a stressful event, as it means going to the ground and risking detection by predators—which puts their lives on the line. Worse, that slow bowel motility means they’re trying to push out nearly one-third of their body weight in feces at a time. It's something to consider the next time you feel envious of their chill lifestyle.

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