And now I am reading an explanation on one of the sites on this picture. They write this: at the moment lightning strikes the sand, there is such an explosion. The path of the lightning strike freezes in the air, covered with a crust of sand. Inside the crust itself, there is a cavity covered with natural glass crystals called "fulgurite".
Sometimes they show another picture like this:
In fact, all this has nothing to do with fulgurites and lightning. The first picture is generally a sand sculpture:
There are many more similar creations of man, take a look.
This is what a place in the ground where lightning struck looks like:
Promotional video:
Now let's get back to real fulgurites. They really arise from a lightning strike.
Fulgurites (English Fulgurite) - hollow tubes in the sand, consisting of melted silica, and melted surfaces on outcrops, formed by lightning. The inner surface is smooth and melted, and the outer is formed by grains of sand and foreign inclusions adhering to the melted mass. The diameter of the tubular fulgurite is not more than a few centimeters, the length can be up to several meters, there have been individual finds of fulgurites 5-6 meters long.
During a lightning discharge, 10 (to the 9th power) -10 (to the 10th power) joules of energy are released. Lightning can heat the channel through which it travels to 30,000 ° C, five times the temperature on the surface of the Sun. The temperature inside the lightning is much higher than the melting point of sand (1600-2000 ° C), but whether the sand melts or not depends on the duration of the lightning, which can range from tens of microseconds to tenths of a second. The amplitude of the lightning current pulse is usually equal to several tens of kiloamperes, but sometimes it can exceed 100 kA. The most powerful lightning and cause the birth of fulgurites - hollow cylinders of melted sand.
Fulgurite, often carefully dug out of the sand, resembles a tree root or a branch with numerous branches. Such branched fulgurites form when a lightning strike strikes wet sand, which is known to have a higher electrical conductivity than dry sand. In these cases, the lightning current, entering the soil, immediately begins to spread out to the sides, forming a structure similar to the root of a tree, and the fulgurite born in this case only repeats this shape. Fulgurite is very fragile and attempts to remove adhering sand often lead to its destruction. This is especially true for branched fulgurites formed in wet sand.
The longest of the excavated fulgurites went underground to a depth of more than five meters. Fulgurites are also called fusion of solid rocks formed by a lightning strike; they are sometimes found in large numbers on the rocky peaks of the mountains. Fulgurites, composed of fused silica, are usually tapered tubes as thick as a pencil or a finger. Their inner surface is smooth and melted, and the outer is formed by grains of sand adhering to the melted mass.
The color of fulgurites depends on the admixture of minerals in the sandy soil. Most of them are reddish-brown, gray or black, but greenish, white or even translucent fulgurites are found.
“A strong thunderstorm has passed, and the sky above us has already cleared. I walked across the field that separates our house from my sister-in-law's. I walked about ten yards along the path when suddenly my daughter Margaret called me. I stopped for about ten seconds and barely moved on, when suddenly a bright blue line cut through the sky, with the crash of a twelve-inch cannon, hitting the path twenty paces in front of me and raising a huge column of steam. I went further to see what mark the lightning had left. Where the lightning struck was a spot of burnt clover about five inches in diameter, with a half-inch hole in the middle …. I went back to the lab, melted eight pounds of tin and poured it into the hole … What I dug out when the tin solidified looked like a huge, slightly curved dog arapnik, heavy as it should be in the handle and gradually converging towards the end. It was slightly longer than three feet (cited from W. Seabrook. Robert Wood. - M.: Nauka, 1985, p. 285).
Employees of the Autonomous University of Mexico have revealed new details of the history of the emergence of the Sahara Desert. According to them, 15 thousand years ago, the Sahara (at least that part of it that is located in the south-west of Egypt) was in an area of temperate climate and could please the eye not with sand dunes, but with a variety of vegetation. For their research, a team of chemists led by Dr. Rafael Navarro-Gonzalez found "frozen" lightning, or fulgurite.
Apparently, the first description of Fulgurites and their connection with lightning strikes was made in 1706 by Pastor David Hermann. Subsequently, many found fulgurites near people struck by lightning. Charles Darwin, while traveling around the world on the Beagle, discovered on the sandy coast near Maldonado (Uruguay) several glass tubes extending vertically down more than a meter into the sand. He described their size and associated their formation with lightning strikes. The famous American physicist Robert Wood was "autographed" by a lightning bolt that nearly killed him.
In addition to a visual demonstration of the destructive power of lightning (the melting temperature of sand (quartz) is more than 1700 ° C), the analysis of foreign inclusions and gas bubbles in fulgurite allows you to restore the chemical composition of the original soil, and sometimes even date it. Dating can be done using thermoluminescence.
Found in the Sahara, in southwestern Egypt, fulgurite was about 15,000 years old. Analysis of gas inclusions in this specimen suggested (based on the high content of carbon compounds) that at the time of the birth of this fulgurite, vegetation existed on the site of the modern desert.
Fulgurites and belemnites are often confused. The tradition of this confusion stems from pre-Christian times, when the fossil belemnites were called "arrows of Perun", and their origin was explained by the incorruptibility of divine weapons.
Sometimes tektites, which are formed as a result of soil melting during a volcanic eruption, explosion, meteorite impact, etc., are given as fulgurites. impact. There may be stories about lightning accompanying pyrocluster flows and clouds of hot gas and dust formed during atomic explosions.
It should be understood that currents in lightning accompanying volcanic eruptions are not strong enough to form fulgurites. Electric discharges during nuclear tests are directed from the ground into the air, and therefore do not lead to melting of rocks.
Despite the ongoing thunderstorm activity, the appearance of fulgurites is a rare phenomenon. Geologists use fossil fulgurites as an object of research: gas bubbles preserved in frozen melts provide valuable information on the composition of the soil and atmosphere in previous eras.
Modern fulgurites of unusual shape and reliable origin cost a lot of money. At the same time, in most cases, buyers are offered a varied and inexpensive counterfeit - from glass tubes melted on a burner and rolled in sand to simple fragments of metallurgical and glass slag.
Chalk-sand hills, as a rule, are completely devoid of groundwater, and if powerful lightning strikes such a hill before the rain begins, fulgurite can turn out in the form of a bizarre ingot of hardly noticeable porosity. Similar fulgurites are also formed in hard rocks exposed to lightning. Such formations are called petrofulgurites.
Petrofulgurites of the andesite summit of Small Ararat are greenish glassy formations - so numerous that even the term "fulgurite andesite" was born.
Relatively low-melting materials can form fulgurites, which are shaped like a piece of solidified foam or pumice. True, the structural differences in the structure of such a fulgurite make it possible to clearly distinguish the central zone of the highest heating of the rock.