Did you know that lightning can be found in the ground? This is called fulgurites
See how they look …
Fulgurites (Engl Fulgurite.) - hollow tubes in the sand consisting of silica melted and fused on the surface of the rock outcrops, formed by the action of 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, 109-1010 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.
The appearance of a glass tube in the sand during a lightning discharge is due to the fact that there is always air and moisture between the grains of sand. The lightning electric current in a split second heats air and water vapor to enormous temperatures, causing an explosive increase in air pressure between grains of sand and its expansion. The expanding air forms a cylindrical cavity inside the molten sand, and subsequent rapid cooling fixes the fulgurite, a glass tube in the sand.
Fulgurite, often carefully dug out of the sand, resembles a tree root or a branch with numerous branches. These branched fulgurites are formed when a lightning strike hits 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 that is 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.
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Fulgurites are sometimes also referred to as melting of solid rocks, marble, lavas, etc. (petrofulgurites), formed by a lightning strike; such melting is sometimes found in large quantities on the rocky peaks of some mountains. For example, the andesite that forms the summit of Small Ararat is penetrated by numerous fulgurites in the form of green glassy passages, which is why it received the name of fulgurite andesite from Abikh.
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.
Fulgurites (pictured) are sand caked from a lightning strike. The melting temperature of the sand is about 1700 ° C, the power of the electric charge is enough to melt it. Therefore, hollow branched glass tubes are formed in the thickness. Their inner surface is smooth, but the outer one is rough, since it is formed by grains of sand adhering to the melted mass. In addition, such lightning frozen into the sand also fixes many other natural inclusions characteristic of a particular stage of geological history.
The fulgurite discovered by Navarro-Gonzalez was different from the usual lightning marks. Egyptian fulgurite contained small bubbles.
With the help of a laser, scientists opened the bubbles and found a gas mixture of carbon oxides, carbon monoxide and nitrogen oxides in them. As noted by the chemist, these substances could be formed as a result of the oxidation of organic substances when heated.
An analysis of the ratio of carbon isotopes in the compounds showed Navorro-Gonzalez and his colleagues that at the time of the lightning strike, the affected area should have been grass, shrubs and other vegetation characteristic of semi-arid areas. It should be noted that now in this area of the Sahara Desert, such plants in no way can grow. And scientists decided to calculate the time in order to understand when grass grew on the site of the Sahara.
To establish the date of the occurrence of the electric discharge, a member of the research team, geochronologist Shannon Megan from the Geological Research Center in Denver (USA) used the thermoluminescence method - he heated the fulgurite to 500 ° C and estimated the energy of electrons "heated" by natural radiation, which was released as light during heat treatment. Its amount directly indicates the moment of the last heating. In this case, it happened at the time of a lightning strike, which happened 15 thousand years ago.
Fulgurite analysis once again confirmed the theory that the Sahara was not so long ago a perfectly habitable region with a temperate climate.
According to Steve Foreman, a geochronologist at the University of Illinois at Chicago, scientists from Mexico City demonstrated a new approach to studying the ecological situation of that period and drew the attention of other researchers to the previously unexplored possibilities of fulgurites.
As for the comments of the representatives of Russian science, then, as noted in a conversation with the correspondent of "Gazeta. Ru" KFMN, employee of the Research Institute of Physics of the Earth RAS Sergei Tikhotsky, from the point of view of physics, the Navarro-Gonzalez team acted competently: “Everything that was done by scientists is included into a classical model for determining the composition and age of a substance,”he said. Accordingly, no falsifications and hoaxes can be noted in the course of this isotope analysis - rather, this is a completely traditional way of research.
The staff of the Institute of Atmospheric Physics of the Russian Academy of Sciences also confirmed to Gazeta. Ru the validity of the theory of the international team of scientists. According to the senior researcher of the laboratory of climate theory Sergei Demchenko, 15 thousand years ago, vegetation could have existed on the territory of Southwestern Egypt.
Moreover, even during the Holocene period (about 6 thousand years ago), this area could be located within the temperate climatic zone.
As a colleague of Demchenko, KFMN Aleksey Eliseev, clarified, vegetation in various areas of the Sahara Desert was present at different times, and, for example, on the Arabian Peninsula, vegetation was preserved until the era of Alexander the Great.
As for the figure of 15 thousand years, here scientists noted that the end of the last ice age belongs to this time. This indirectly confirms the Navarro-Gonzalez theory, so that in general, the discovery of Mexican scientists can be classified as verifiable.
Details of the study by Dr. Navarro-Gonzalez's team can be found in the journal of the Geological Society of America.
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.
For example, here's how lightning can strike a house:
But in the car:
But in a person:
But the photographers were just lucky: