What happens when lightning strikes sand?


Quick Answer

When lightning strikes a sandy beach high in quartz or silica, it can fuse the sand into silica glass. The resultant tube of glass covered in sand is called a fulgurite. Fulgurites can have many branches or be a simple tube.

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Full Answer

To form fulgurite from a lighting strike, the temperature must rise above 1,800 degrees Celsius, or 3,270 degrees Fahrenheit, and then cool, all within the span of about one second. Photos of fulgurite standing on the beach typically show it mostly exposed above the beach; however the initial formation occurs beneath the surface of the sand. Over time, erosion occurs, and the material surrounding a fulgurite is removed, making it visible.

Glass is fairly resistant to water erosion, so small formations of fulgurite can last for quite some time before being discovered, but it is fragile, so larger formations often break after they are revealed. There have been claims of fulgurite photos on the Internet are later proven to be false. The more ornate and bigger the object appears, the less likely it is to be fulgurite. Another indication that a photo may be a hoax is happy swimmers nearby or the lack of a scientific team taking the photo.

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