CLOSE
Original image
Barcroft TV, Youtube

The Science Behind Super Rare (and Totally Amazing) Volcanic Lightning

Original image
Barcroft TV, Youtube

Recently, a viral video of rare volcanic lightning footage has been making the rounds on social media. It’s easy to see why. The dramatic clip appears to show flecks of lightning dancing though an ominous volcanic plume, the likes of which most viewers have never seen. Make that all viewers, actually: As it turns out, the clip was actually doctored by the BBC, which combined footage from two separate eruptions for a scene in their hit series Patagonia: Earth’s Secret Paradise.

Nonetheless, volcanic lightning—a phenomenon that’s also known as a “dirty thunderstorm”—is still very real. Here’s what the incredible display actually looks like:

Back in March, German photographer Marc Szeglat captured the spectacle above, which is the Sakurajima volcano, located on Kyushu, Japan’s third-largest island. (Before 1914, the volcano sat on a smaller island named Sakurajima, but a huge eruption that year merged the landmass with Kyushu proper.)

A seasoned volcano photographer, Szeglat set out to document a Sakurajima blast and, in the process, also captured one of nature’s most mysterious wonders. At 2:05 in the video, you can see a lightning bolt zig-zagging across the eruption’s ashy mushroom cloud. 

What’s going on here? Believe it or not, some volcano-generated plumes are capable of creating powerful electrical charges that can lead to streaks of lightning, and bolts as large as two miles long.

As Szeglat explained to the BBC, “In a normal thunderstorm ice crystals collide and generate electrical charges, which results in lightning. In an eruption cloud, ash particles collide instead of ice crystals.”

But how do these particle collisions actually produce lightning? Experts aren’t entirely sure. “How lightning forms in general is still debated among scientists,” writes geologist Brentwood Higman on Geology.com, “and volcanic lightning is even less well understood.”

Still, we can say with reasonable certainty that all dirty thunderstorms require what’s known as a pyroclastic flow—fast-moving volcanic currents consisting of hot gas, rock fragments, and ash.  They’re also incredibly dangerous, as the billowing clouds tend to “hug” the ground and bury everything in their path. Such flows famously descended upon Pompeii in 79 CE, while others surged forth from Mount St. Helens during its sky-darkening 1980 eruption

As tiny particles are kicked into the atmosphere, they begin to move apart or split in two. The positively charged particles separate from their negatively charged brethren, and eventually build up enough attraction to cause a serious spark. According to Higman, “Lightning is the electrical flow that results when this charge separation becomes too great for air to resist the flow of electricity.”

Well-documented dirty thunderstorms broke out at Mount Redoubt of Alaska in 2009 and Iceland’s Eyjafjallajökull in 2010. Masses of round, glassy beads were later discovered at both sites, and earlier this year, an international scientific team concluded that the spherules had been forged by volcanic lightning. In theory, the incredibly hot bolts (whose scalding temperatures can reach 30,000°C) melted down pieces of ash which then re-solidified as little glass balls. 

Recent research also suggests that volcanic lightning bolts come in at least two distinct types. Some—like these—dart about near the tops of plumes. Meanwhile, others simply hang around the volcano’s mouth.

Volcanic lightning storms can also demonstrate the kind of intensity that’s normally reserved for Midwestern tempests. Unfortunately, filming them in action has proven exceptionally difficult, with flashes of lightning being too quick for most recording devices. So while the BBC did embellish that footage, it's likely that a "super-charged volcanic ash cloud" (!) could really be that spectacular—we'd just have to record it first to see.

Original image
iStock
arrow
science
Geological Map Shows the Massive Reservoir Bubbling Beneath Old Faithful
Original image
iStock

Yellowstone National Park is home to rivers, waterfalls, and hot springs, but Old Faithful is easily its most iconic landmark. Every 45 to 125 minutes, visitors gather around the geyser to watch it shoot streams of water reaching up to 100 feet in the air. The punctual show is one of nature’s greatest spectacles, but new research from scientists at the University of Utah suggests that what’s going on at the geyser’s surface is just the tip of the iceberg.

The study, published in the journal Geophysical Research Letters, features a map of the geological plumbing system beneath Old Faithful. Geologists have long known that the eruptions are caused by water heated by volcanic rocks beneath the ground reaching the boiling point and bubbling upwards through cracks in the earth. But the place where this water simmers between appearances has remained mysterious to scientists until now.

Using 133 seismometers scattered around Old Faithful and the surrounding area, the researchers were able to record the tiny tremors caused by pressure build-up in the hydrothermal reservoir. Two weeks of gathering data helped them determine just how large the well is. The team found that the web of cracks and fissures beneath Old Faithful is roughly 650 feet in diameter and capable of holding more than 79 million gallons of water. When the geyser erupts, it releases just 8000 gallons. You can get an idea of how the reservoir fits into the surrounding geology from the diagram below.

Geological map of geyser.
Sin-Mei Wu, University of Utah

After making the surprising discovery, the study authors plan to return to the area when park roads close for the winter to conduct further research. Next time, they hope to get even more detailed images of the volatile geology beneath this popular part of Yellowstone.

Original image
iStock
arrow
Big Questions
Just How Hot Is Lava?
Original image
iStock

Like the bubbling cheese of a pizza consumed too quickly, lava has been anointed as one of the most scorching substances on Earth. But just how hot is lava? How quickly could it consume your flesh and destroy everything in its path?

You may already know that lava is actually molten rock that oozes or spurts out of volcanoes because of the extreme temperatures found miles deep in the Earth. As the rocks melt, they begin to rise toward the surface. (Lava is typically referred to as magma until it reaches the surface.) As you can imagine, the heat that's needed to melt rock is pretty staggering. Cooler lava—relatively speaking—could be around 570°F, about the same as the inside of your typical pizza oven. On the extreme side, volcanoes can produce lava in excess of 2120°F, according to the United States Geological Survey.

Why is there so much variation? Different environments produce different chemical compositions and minerals that can affect temperature. Lava found in Hawaii from basalt rock, for example, tends to be on the hotter side, while minerals like the ones found near the Pacific Northwest's Mt. Saint Helens could be a few hundred degrees cooler.

After lava has erupted and its temperature begins to lower, it will eventually return to solid rock. Hotter lava flows more quickly—perhaps several feet per minute—and then slows as it cools, sometimes traveling only a couple of feet in a day.

Because moving lava takes its sweet time getting anywhere, there's not much danger. But what if you did, in some tremendously unfortunate circumstance, get exposed to lava—say, by being thrown into a lava pit like a villain in a fantasy film? First, you're unlikely to sink rapidly into it. Lava is three times as dense as water and won't simply move out of the way as quickly. You would, however, burn like a S'more at those temperatures, even if you wouldn't quite melt. It's more likely the radiant heat would singe you before you even made contact with the hypothetical lava lake, or that you'd burst into flames on contact.

Because lava is so super-heated, you might also wonder how researchers are even able to measure its temperature and answer the burning question—how hot is lava, exactly—without destroying their instrumentation. Using a meat thermometer isn't the right move, since the mercury inside would boil while the glass would shatter. Instead, volcanologists use thermocouples, or two wires joined to the same electrical source. A user can measure the resistance of the electricity at the tip and convert it to a readable temperature. Thermocouples are made from ceramic and stainless steel, and both have melting points higher than even the hottest lava. We still don't recommend using them on pizza.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios