Fossilized Lightning

Lightning must hover near the top of any list of the most ephemeral phenomena. The discharge of static electricity during storms is so fast we use it in one of our most cliched idioms: lightning quick.

On the other end of the spectrum are entities that persist for long durations, such as rocks or plastics. Through the magic of chemistry, some organic bodies can be preserved as fossils for millions of years. Think of the dinosaur bones that hang in museums or mosquitoes trapped in Jurassic Park amber.

A bolt of lightning is comprised of electrons moving from cloud to cloud or cloud to ground. Things get so gnarly during the events that gases in the air morph into plasma, which forms a channel that allows the electrons to flow. The visible light we see is a form of electromagnetic radiation called black-body radiation. The median length for a strike is just 0.52 seconds.

The title of today’s examination seems to present a conundrum. How can something made of electrons, with such a short duration, ever become fossilized?

Strokes of cloud-to-ground lightning strike the Mediterranean Sea - photo by Maxime Raynal

Presented for your consideration are fulgurites.

From the Latin word for “lightning” – fulgur – these structures are more like the bodies at Pompeii than true fossils. The famous remnants of the volcanic eruption that leveled the cities of Pompeii and Herculaneum are preserved by ash shells. The hot material caught unsuspecting humans by surprise, killing them in strange positions. Over time, the organic material of the people deteriorated but the hard ash around the bodies remained.

Fulgurites are not the preserved remains of a lightning bolt but they often represent the shape of the event. When a bolt impacts the ground, if conditions are right, the lightning is so hot that it can morph soil chemistry. Depending on the makeup of the ground, the sediment or rock can be vitrified – turned into glass – or fused. The result is a hardened clump of soil. Sometimes, the fulgurite takes the form of a tube, which mimics the “appearance” of the lightning bolt.

Sand fulgurites in Algeria - photo by Stickpen
A tubaceous fulgurite in California - photo by M.O. Stevens

In a shock to no one, lightning can become very hot. Peak temperatures inside the plasma channel can exceed 50,000 degrees Fahrenheit (27,800 degrees Celsius). These temperatures can melt or fuse rocks, minerals, and sediments that typically never leave the solid phase on Earth. Fulgurites present in two major forms. Sometimes they create clumps or masses on the surface of the soil, almost like the hardened surface of a baked muffin. Other times, the bolts penetrate the ground and leave their imprint in the soil, creating tubes and branches.

The color of a fulgurite varies widely because it depends on the mineral makeup of the struck soil. If the ground has iron, the fulgurite will likely be dark brown or deep green. If the bolt hits a sandy area, the fulgurite will probably be closer to white. The fossilized lightning can produce odd, bright colors if bolts hit synthetic materials. Downed power lines, which possess the power of a lightning bolt, can make wildly colored fulgurites because of the concentration of copper in the wires.

Despite the frequency of lightning strikes around the world – 1.4 billion times per year! – many people will never have encountered a fulgurite. They tend to be tiny and brittle. However, we have uncovered rather large samples. A specimen in Florida measured 16 feet in length. Yale University’s Peabody Museum of Natural History boasts a 13-foot root. Although not continuous, fulgurite pieces in Michigan at Winans Lake covered an area about 90 feet in length! This discovery featured a piece 16 feet long and a foot thick, potentially the biggest mass of fulgurite ever uncovered.

Imagine if this system remained connected! Envisioning the power of a bolt of lightning seems beyond our abilities; picturing the flash that created fulgurites 16 feet long and a foot thick might be impossible. To take the power of lightning to another level, fulgurites have formed almost 50 feet below the surface of a strike!

I could not verify the veracity of this photo, but a user on Reddit claims the following image is a fulgurite. It might be the specimen from the Peabody Museum, as the photo seems to display a legitimate museum setting and the dimensions appear plausible for its size. However, no official images seem to exist on the net.

A photo purportedly displaying a massive fulgurite - photo by Abhay/Reddit

Despite the fragility and relative rarity of these lightning chunks, the enterprising collector can find them to purchase for shockingly cheap prices. eBay listings abound, with many under $10. A fulgurite could be a fantastic gift for mineral lovers or general nature enthusiasts. For $10,000, you could buy a fulgurite claimed to be the world’s longest known at 23 feet.

Many of the materials that scientists find in fulgurites, such as shocked quartz, silicides, and the beautifully named buckminsterfullerenes, only show up in the most bodacious circumstances. Nuclear weapon detonations. Hypervelocity impacts (e.g. meteor craters). Or floating around interstellar space after a God-knows-what-event. Such is the power of the lightning bolt.

May the extent of your close encounters with lightning be restricted to fulgurites!

Fulgurites from the Sahara Desert - photo by John Alan Elson
Specimens from the Mauritanian desert - photo by Ji-Elle
A massive tubular fulgurite in Japan - photo by SelEle-MS

Further Reading and Exploration


PETRIFIED LIGHTNING by Peter E. Viemeister

More about Fulgurites – The Agatelady

Fulgurites – Fossils Plus

Petrified Lightning – Mini Museum

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