We all know of the effect of the heat of the atomic bomb that exploded on the New Mexican desert in 1945. We have seen pictures of the green glass formed on the sand around the area of the explosion. It is interesting to note that, long before man, lightning has been producing vitrified crusts on the surfaces of rocks, and still does produce glassy masses when a bolt strikes a rock outcrop. If lightning strikes a sandy area, it often does more than produce a glassy mass. It penetrates the sand, sometimes to a depth of many feet, with the resultant formation of a fused sand tube called a fulgurite.
Not all areas struck by lightning produce these peculiar tubes. The sandy area must be non-conducting; that is, the material must not be such that the electric current is conducted away from the point of contact with the earth. To form a tube the lightning must continue down through the relatively non-conducting sand as a bolt, fusing the surrounding material into molten sand as it progresses. As the fused material cools, it forms a glass of varying surface features. The very small amount of water in the sand, or associated with it, is vaporized quickly. In some cases, by its expansion, the water produces bulges in the walls of the fused material. Lightning tubes vary considerably in physical characteristics. They may be from a few inches to forty-five feet in length, from one-quarter inch to two and one-half inches in diameter; and may have walls varying from paper thickness to one-tenth of an inch.
The irregular shape can easily be explained by the fact that lightning follows the path of least resistance as it finds it in the texture and arrangement of the material that comprises the sand dunes in which most of the fulgurites occur. The cross-section of the tube is generally circular, and the fulgurite, throughout its length, may be relatively straight, sometimes branched and, often, more or less serpentine or spiral. Usually the tubes taper toward the end and finally close at the tip, but at intervals the walls may collapse, thus closing the tube. Most frequently fulgurites are a translucent white to pearl-gray, but they may be yellowish, reddish, green, or brown, the latter colors being produced by varying percentages of iron in the sand. The rather rare, black tubes are produced when the tube is formed in earth containing carbonaceous material, or when the tube is in contact with the root of a tree or vine. Sometimes the coloring is banded lengthwise.
David is the author of many articles including Best Friend Quotes and also the author of Best life quotes
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