If you’ve ever walked on a beach or through a sandy desert, chances are you’ve stepped over the remnants of lightning.
Fulgurites are shards of melted sand, rock and debris found on beaches where lightning has struck. As the bolt reaches the ground, as much as a hundred million volts are discharged into whatever it strikes, where the bolt itself could reach up to five times the temperature of the Sun’s surface.
If the conditions are right (the sand reached above 1800 degrees Celsius), the bolt could instantaneously vitrify silica-rich sand, which results in the production of thin branches of glassy solids buried in the sandy ground. The branches can reach up to 15m into the ground, but are usually too fragile to remove without breaking. When the sand supporting the brittle structure is removed, the glass is unable to support its own weight and can shatter. This is why most fulgurites are only a few centimeters in length, with longer ones reaching around 75cm. The longest fulgurite (4.9m) was found in Florida in 1996.
Fulgurites can also be formed artificially with high voltage rods, as shown in the video:
Fulgurite comes from the Latin word fulgur, which means Lightning
By Sonam Okuda, Y13 at BPS
Image: Alden, Andrew. 2019. What Are Minerals? [Online] Last accessed: October 2020
Available from: https://www.thoughtco.com/what-are-minerals-1440987
Rafferty, John P. Fulgurite. [Online] Last accessed: October 2020
Available at: https://www.britannica.com/science/fulgurite
Chaotic Good. 2013. Making Fulgurites with High Voltage [Online] Last accessed: October 2020