Continued from the files of Don Kirk…
…The fulgurites here are light gray in color. I can see through them to the gray-brown lava rock beneath. They look like somebody poured molten glass on this lava outcrop. Sitting on one of these deposits of natural glass makes me a little ill at ease. I shiver a bit, knowing a powerful lightning bolt once stuck this very spot. Had I been here…well, I’d be worse than toast. I know that today there are no clouds anywhere in the visible sky, but I look around anyway, checking it out. Everything looks quite pleasant, meaning safe, no clouds.
Rock fulgurites are usually described as a very thin layer on the volcanic rock. Yet I see here a fulgurite that has broken into two pieces. This layer of natural glass is at least one–eighth of an inch thick, not a ‘thin layer’ to my mind. Fulgurites are often colors other than gray, such as red, depending on the composition of the rocks beneath.
Sand fulgurites radiate downward and outward in the sand beneath a lightning strike. The super heated moisture and air in the sand expand explosively, forming tubes lined with molten glass. The diameter of the tubes varies from a quarter of an inch to more than 3 inches. Sand fulgurites are extremely fragile. Great care is needed when excavating them. In sandy areas where lightning is frequent and wind regularly moves the sand dunes it is rare to find a large, unbroken fulgurite, but good–sized fragments may be common.
Since sand and rock fulgurites are true glass, they are quite resistant to erosion and can last for a long time in nature. Because of their durability, fulgurites tell us something about the past. Sand fulgurite fragments are common in the Sahara Desert, where today there is very little lightning. This shows that at some time in the past, the Saharan Desert weather was quite different than it is today.
The fulgurites on this lava outcrop are very well preserved. They look like they could have been made yesterday. I must show the children. I walk over to within calling distance. They leave their game of sagebrush tag and come running. End.