On June 30th 1908, an explosion with the force of over one thousand atomic bombs which its heat and brightness was comparable to the sun. It shook the wilderness of Tunguska, Siberia, with the same effects of a 5.0 magnitude earthquake. Millions of trees fell in every direction and dust from the explosion lit up the night sky, visible from as far away as London.
Known as The Tunguska event, it occurred early in the morning over the sparsely populated Eastern Siberian Taiga and flattened eight hundred and thirty square miles of forest. Despite the level of destruction no human fatalities were officially documented.
Although no impact crater was dicovered, the explosion has been attributed to the air burst of a meteoroid and has been classified as an impact event. What ever the object was, it is thought to have disintegrated at an altitude of three to six miles rather than hitting the surface of the Earth.
The Tunguska event is the largest impact event on Earth in recorded history. Studies have yielded different estimates of the meteoroid’s size, on the order of 60 to 190 meters, depending on whether the body was a comet or a denser asteroid, but no one can be completely sure.
At breakfast time I was sitting by the house at Vanavara Trading Post [65 kilometres/40 miles south of the explosion], facing north. […] I suddenly saw that directly to the north, over Onkoul’s Tunguska Road, the sky split in two and fire appeared high and wide over the forest [as Semenov showed, about 50 degrees up—expedition note]. The split in the sky grew larger, and the entire northern side was covered with fire. At that moment I became so hot that I couldn’t bear it as if my shirt was on fire; from the northern side, where the fire was, came strong heat. I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few meters. I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn, a part of the iron lock snapped. – Testimony of S. Semenov, as recorded by Leonid Kulik’s expedition in 1930.
We had a hut by the river with my brother Chekaren. We were sleeping. Suddenly we both woke up at the same time. Somebody shoved us. We heard whistling and felt strong wind. Chekaren said, ‘Can you hear all those birds flying overhead?’ We were both in the hut, couldn’t see what was going on outside. Suddenly, I got shoved again, this time so hard I fell into the fire. I got scared. Chekaren got scared too. We started crying out for father, mother, brother, but no one answered. There was noise beyond the hut, we could hear trees falling down. Chekaren and I got out of our sleeping bags and wanted to run out, but then the thunder struck. This was the first thunder. The Earth began to move and rock, the wind hit our hut and knocked it over. My body was pushed down by sticks, but my head was in the clear. Then I saw a wonder: trees were falling, the branches were on fire, it became mighty bright, how can I say this, as if there was a second sun, my eyes were hurting, I even closed them. It was like what the Russians call lightning. And immediately there was a loud thunderclap. This was the second thunder. The morning was sunny, there were no clouds, our Sun was shining brightly as usual, and suddenly there came a second one!
Chekaren and I had some difficulty getting out from under the remains of our hut. Then we saw that above, but in a different place, there was another flash, and loud thunder came. This was the third thunder strike. Wind came again, knocked us off our feet, struck the fallen trees.
We looked at the fallen trees, watched the tree tops get snapped off, watched the fires. Suddenly Chekaren yelled “Look up” and pointed with his hand. I looked there and saw another flash, and it made another thunder. But the noise was less than before. This was the fourth strike, like normal thunder.
Now I remember well there was also one more thunder strike, but it was small, and somewhere far away, where the Sun goes to sleep. – testimony of Chuchan of Shanyagir tribe, as recorded by I. M. Suslov in 1926
The first recorded expedition to the scene arrived more than a decade after the event. In 1921, the Russian mineralogist Leonid Kulik, while visiting the Tunguska River to complete a survey for the Soviet Academy of Sciences, deduced from local accounts that the explosion had been caused by a giant meteorite impact. He persuaded the Soviet government to fund an expedition to the Tunguska region, based on the prospect of meteoric iron that could be salvaged to aid Soviet industry. Kulik’s party eventually undertook the expedition in 1927.
Upon arrival, Kulik made arrangements with the local Evenki hunters to guide his party to the impact site. Reaching the explosion site was an extremely arduous task. As soon as they arrived in an area just south of the site, the superstitious Evenki hunters refused to go any farther. They were in terrible fear of what they called the Valley-men. Kulik had to return to the nearby village to find his party new guides, delaying them for several days.
To Kulik surprise as he stood on a ridge overlooking the devastated area, there was no crater. Instead around ground zero was a large five mile area of trees. Although scorched and devoid of branches, they were standing upright. The trees farther away had been partly scorched and knocked down in a direction away from the center. Kulik then located holes that he erroneously concluded were meteorite holes. Unfortunately he did not have the means to excavate the holes at that time.
Three more expeditions to the area were conducted over the next ten years. Kulik found several dozens of little “pothole” bogs, each were roughly five to ten meters in diameter, that he thought might be meteoric craters. After a laborious exercise in draining one of these bogs (referred to as “Suslov’s crater”), he found an old stump on the bottom, ruling out the possibility that it was a meteoric crater. In 1938, Kulik arranged for an aerial photographic survey of the area covering the central part of the leveled forest, an area of about ninety seven square miles. The one thousand five hundred negatives of these aerial photographs, each 18 by 18 centimeters were burned in 1975 by order of Yevgeny Krinov, who at the time was the Chairman of the Committee on Meteorites of the USSR Academy of Sciences, as part of an initiative to dispose of hazardous nitrate film. Positive prints were preserved for further study in the Russian city of Tomsk.
Expeditions sent to the area in the 1950s and 1960s found microscopic silicate and magnetite spheres when sifting through the soil. Similar spheres were predicted to exist in the felled trees, although they could not be detected by contemporary means. Later expeditions did identify such spheres in the resin of the trees and chemical analysis showed that the spheres contained high proportions of nickel relative to iron, which is also found in meteorites. These findings lead to the conclusion they were of extraterrestrial origin. The concentration of the spheres in different regions of the soil was also found to be consistent with the expected distribution of debris from a meteoroid air burst. Later studies of the spheres found unusual ratios of numerous other metals relative to the surrounding environment, which was taken as further evidence of their extraterrestrial origin.
Chemical analysis of peat bogs from the area also revealed numerous anomalies considered consistent with an impact event. The isotopic signatures of stable carbon, hydrogen, and nitrogen isotopes at the layer of the bogs corresponding to 1908 were found to be inconsistent with the isotopic ratios measured in the adjacent layers, and this abnormality was not found in bogs located outside the area. The region of the bogs showing these anomalous signatures also contains an unusually high proportion of iridium, similar to the iridium layer found in the Cretaceous–Paleogene boundary. These unusual proportions are believed to result from debris from the falling body that deposited in the bogs. The nitrogen is believed to have been deposited as acid rain, a suspected fallout from the explosion.
Researcher John Anfinogenov believes that a boulder found at the event site, known as John’s stone, is possibly a remnant of the meteorite.
Of course many theories exist. Some people have suggested it could have been related to extraterrestrial beings, perhaps a crashed UFO. Astrophysicist Wolfgang Kundt has a more down to earth theory. He proposed that the Tunguska event was caused by the release and subsequent explosion of 10 million tons of natural gas from within Earth’s crust. Wolfgang theorised that natural gas leaked out of the crust and then rose to its equal-density height in the atmosphere; from there, it drifted downwind, in a sort of wick, which eventually found an ignition source such as lightning. Once the gas was ignited, the fire streaked along the wick, and then down to the source of the leak in the ground, whereupon there was the explosion.
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