Lightning forms fulgurites in the sands of beaches and deserts
I have to admit, my interest in this topic came less from scientific inquiry and more from watching the movie "Sweet Home Alabama" one too many times. In the movie, lightning strikes the sand, creating beautiful, clear, root-like structures. As it turns out, this is actually fact rather than fiction, but the real-life products, called fulgurites, aren't as pretty. They're still pretty neat, though.
Sand fulgurites form when lightening of 1,800 degrees Celsius or more strikes quartz sand. The silica melts instantaneously, causing sand grains to fuse together. The process takes about a second. Fulgurites have also been known to occur when electrical lines fall into the sand.
Fulgurites are rough and porous on the outside and usually smooth glass on the inside. Sometimes, the interior is bubbly. The glassy interior forms due to the rapid cooling and solidification of the sand. The smooth glass is called lechatelierite, or silica glass. It is also formed when meteorites impact the earth, but it's known as tektite when it is formed this way. Fulgurites can vary in color from black, tan, green, and translucent white.
The size of fulgurites depends on the lightning's strength when it strikes and the depth of the sand bed. The longest fulgurite found was approximately 17 feet in length and found in Florida. It was created by artificially triggering lightning during an experiment the University of Florida has dubbed, "The Event."
Fulgurites are most commonly found on beaches or in deserts. Tampa, Florida boasts the highest levels of lightning in the United States. Fulgurites are plentiful in the Sahara Desert where little lightning activity occurs today. This confirms the fact that climate conditions in the Sahara were remarkably different in prehistoric times.
The next time I'm at the beach, I plan to look for fulgurites. Have you ever found a fulgurite? If so, how big was it?
Photo courtesy of the University of Florida.