Why Volcanoes Sometimes Shoot Out Lightning
When Mount Vesuvius erupted in 79 AD, Pliny the Younger described the cataclysmic event, writing: “There was a darkness of the most intense nature, rendered more dreadful by the intermittent glow of the torches at intervals obscured by the passing glare of lightning.” » Although Pliny may not have known it, lightning is also common during volcanic eruptions and sandstorms. But what is the cause? A study recently published in Nature highlights this strange phenomenon.
Scott Waitukaitis of the Austrian Institute of Science and Technology experimented with silicon dioxide (also known as quartz), a major component of sand and volcanic ash. Silicon dioxide is an electrical insulator, meaning it does not conduct electricity. When two quartz particles meet, they should not exchange electrical charge. And yet they do it.
To study how these crystals can produce a spark, Waitukaitis and his team levitated tiny quartz grains with sound to avoid contact charging, then subjected them to a battery of experiments. Water, the polarized molecule responsible for lightning from storm clouds, turned out to be a dead end. Eventually, they discovered that heating quartz crystals could produce a negative charge.
Read more: “What volcanoes tell us”
According to the researchers, the reason has little to do with the crystals themselves. Instead, a thin layer of atmospheric carbon was deposited on the quartz, and when it was removed by heat, the crystals became charged. Repeating the experiment with other natural dioxide insulators gave similar results.
“Most of these materials in nature are small particles smaller than a millimeter. They become charged by colliding, rubbing and rolling over each other,” Waitukaitis said in a statement. “This is why desert sand, volcanic ash clouds and dust particles become charged.”
But these discoveries go beyond simply explaining the impressive spectacle of volcanic lightning. In fact, they could help explain how planets form from dust and how primordial amino acids managed to come together and form complex proteins.
“Some current models of planetary formation rely on a predominant charge effect,” Waitukaitis said. “As such, our research might just have shed light on the mechanism behind the sparks of creation.”
Not bad for a few grains of sand.
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Main image: Terje Sørgjerd / Wikimedia Commons
