Most people associate ash and churning lava with volcanic activity, but volcanoes also produce formations that look unnervingly like human ponytails.
Known as Pele’s hair, these extremely thin strands of volcanic glass are named for Pele, a female figure in Hawaiian mythology associated with volcanism. They’ve been reported raining down on yards and filling up rain gutters near volcanic regions in places like Hawaii and Iceland.
According to new research by a team of scientists and glass artists, the delicate-looking structures may form when bubbly magma is stretched. The results of their study were published last month in the journal Geology.
Unlike the glossy black of obsidian, another volcanic glass, Pele’s hair is typically light brown or yellow, and it can rival human locks in length. “We’ve seen some strands up to two feet long,” said Katie Mulliken, a geologist at the U.S. Geological Survey’s Hawaiian Volcano Observatory who was not involved in the research.
The strands can travel long distances with a breeze: Last month, activity on Kilauea volcano on the Big Island of Hawaii produced Pele’s hair that landed in the town of Pahala, about 20 miles away.
Pele’s hair can form when bits of lava are tossed up in the air and then stretched by jets of volcanic gases. “They can get spun out by the wind,” said Janina Gillies, a geologist at the University of Canterbury in New Zealand.
But that process, which creates strands of Pele’s hair of different lengths, did not explain why Pele’s hair was sometimes found in bundles of hundreds, or even thousands, of aligned strands. Ed Llewellin, a volcanologist at Durham University in England, remembers finding one such formation on the Big Island of Hawaii. “I was 100 percent convinced it was a woman’s ponytail lying on the lava,” Dr. Llewellin said. “It was really quite shocking.”
A team led by Dr. Gillies and Dr. Llewellin investigated how bundles of aligned strands of Pele’s hair might form. Maybe, they hypothesized, the stretching of lava without the help of a gas jet could produce the bundles. Maybe, Dr. Llewellin said, “you can start with a foamy, molten glass material and stretch it.”
The idea came from experiments the team did with a sugary, air-filled dessert known as hokey pokey in Dr. Gillies’s native New Zealand. “The proof of concept to see whether we could form this stuff was with sugar,” Dr. Gillies said. “We’d squish it and pull it apart.”
That early work showed that the presence of air bubbles seemed crucial to producing long, sugary strands. And the experiments had the benefit of being relatively safe, Dr. Gillies said, adding, “You’re not going to get your hand burned off.”
Still, more realistic experiments were necessary, and the collaboration grew to include the group of people perhaps most accustomed to working with lava-like material: glass artists.
One was Colin Rennie, an artist affiliated with the National Glass Center at the University of Sunderland in England. Mr. Rennie’s work is often inspired by science. “I’m interested in the ways that humans try to understand the world, whether that be through science or myth,” he said.
Mr. Rennie helped the research team prepare hockey-puck-size pieces of glass containing varying amounts of powdered calcium carbonate. When they were heated in a furnace to roughly 2,000 degrees Fahrenheit, the calcium carbonate decomposed and produced carbon dioxide gas. That created air bubbles in the pucks. “It looked like bread inside,” Dr. Llewellin said, “a particularly artisan bread with lots of big bubbles in it.”
Wearing a suit designed to reflect heat, Mr. Rennie retrieved the pucks from the furnace and slipped them into a steel device he had designed and named the Pullificator. The device stretched the pucks using a weight-and-pulley system. Everything had to happen within about a minute. “You have to choreograph,” Mr. Rennie said.
The team found that when air bubbles filled about three-quarters of the space, the pucks readily formed Pele’s hair-like threads when stretched. But pucks that had far fewer air bubbles formed one wide ribbon of glass. “The more bubbles there are, the more hairs that form,” Dr. Gillies said. That made sense, the team surmised, because it was the glass between the bubbles that had stretched to form the hairs.
Ken Hon, a volcanologist at the Hawaiian Volcano Observatory who was not involved in the research, said the study necessarily involved a simplification of nature. He noted that in real life, a blob of lava is not being pulled straight down with a weight. In the study, “their mechanism isn’t quite right,” he added.
The research team suggested that in the real world, several processes might stand in for the Pullificator. For example, lava is always being stretched because it’s constantly churning, Dr. Llewellin said, adding, “Bits are rising at different rates, and that leads to parts of it stretching.”
Some artists involved in the project have gone on to create pieces inspired by the experiments. For Dr. Llewellin it was immensely rewarding to bring together volcano scientists and glassmaking experts. “We’re fascinated by the same material, just ours comes out of a volcano and theirs is produced in the furnace,” he said.
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