The Tunguska Event Explained: The 1908 Blast, Kulik and the Airburst

The Tunguska event was a huge explosion over the Siberian forest near the Podkamennaya Tunguska River at about 7:14 a.m. local time on 30 June 1908. It flattened roughly 2,150 square kilometres of forest but left no impact crater, and the scientific consensus is that a space rock tens of metres across blew apart in the air several kilometres above the ground. What is still argued over is not whether it was an airburst, but whether the object was a stony asteroid or a fragment of a comet.

Tunguska matters because it is the largest impact event in recorded history, and it happened only a little over a century ago. It is the reference case for how a modest-sized object can devastate an area the size of a large city without touching the ground, and it has attracted more alternative explanations than almost any natural event, from crashed spacecraft to Nikola Tesla. This guide covers what happened, what the expeditions found, what science concludes and where the fringe theories came from.

What happened on 30 June 1908?

On the morning of 30 June 1908 (17 June in the Julian calendar Russia still used), a fireball crossed the sky over central Siberia and exploded over the taiga in what is now Evenkiysky District, Krasnoyarsk Krai. The region was very thinly populated, which is why the death toll was so low. Eyewitness accounts suggest that at most a few people died, possibly up to three, and that damage to property was limited to a handful of buildings.

The best-known witness, a man named Semenov, was at the trading post at Vanavara, about 65 kilometres south of the blast. He described a heat so intense that his shirt felt as if it were on fire, and being thrown by the blast. A local herder closer in described a series of thunderclaps and a hut knocked over. Windows broke hundreds of kilometres away.

Seismic stations across Eurasia registered ground shaking, and barometers picked up the air-pressure wave in places as distant as Britain and Washington, D.C. For several nights afterwards the skies over Europe and Asia glowed so brightly that photographs were reportedly taken at midnight in Sweden and Scotland without a flash. Measurements at Mount Wilson Observatory in California showed a months-long drop in atmospheric transparency, consistent with high-altitude dust.

The flattened zone, surveyed in detail in the 1960s, has a distinctive butterfly shape roughly 70 kilometres across and 55 kilometres long. A figure often repeated online, that 80 million trees were knocked down, traces back to an early estimate that overstated the size of the devastated area several times over and should not be relied on.

What did Leonid Kulik find?

Leonid Kulik, a Soviet mineralogist who specialised in meteorites, led the first scientific investigations of the site, and what he found was not what he expected. In 1921 Kulik led a survey for the Soviet Academy of Sciences into the Podkamennaya Tunguska basin; the team gathered accounts from local people but never reached the centre of the blast.

In 1927 he finally got there. He expected a crater and a large iron meteorite. He found neither. At the centre, across a zone about 8 kilometres wide, trees were still standing but had been stripped of their branches and scorched. Farther out, the trees lay flattened in a radial pattern, their roots pointing toward the centre and their tops pointing away from it. The pattern located the blast's centre even without a crater.

Kulik returned on further expeditions over the following decade. He suspected some of the area's small bogs were meteorite craters, among them a 32-metre bog known as Suslov's crater. When it was drained, an old tree stump was found at the bottom, which ruled out a recent impact. In 1938 an aerial photographic survey covered the central 250 square kilometres of the site.

Why is there no crater? The airburst explanation

There is no crater because the object most likely never reached the ground. The scientific consensus is that a space rock tens of metres across entered the atmosphere at high speed, was heated and compressed by air resistance, and broke apart catastrophically at an altitude of roughly 5 to 10 kilometres. The shock wave travelled downward and outward, which is why trees directly beneath stood upright while those around them were blown over.

How much energy was involved depends on the model. Early estimates put the explosion at about 10 to 15 megatons of TNT, with some reaching higher. Supercomputer simulations at Sandia National Laboratories in 2007, which accounted for the momentum of the incoming object, suggested a lower figure of about 3 to 5 megatons. Other modelling, including a 2019 study by Wheeler and Mathias, has put it as high as 20 to 30 megatons. The honest answer is a range, not a single number. Estimates of the object's size vary accordingly, with many studies favouring a stony body around 50 to 60 metres across.

Estimates of how often such an event happens range from once every few centuries to once in a thousand years; for near-Earth object background, see the earlier piece on a large asteroid compared to the Tunguska event.

Was it an asteroid or a comet?

Scientists agree it was an airburst, but they still debate what kind of object exploded. In 1930 the astronomer Fred Whipple proposed that a small comet was responsible, which would explain why so little solid material was found. In 1978 the Slovak astronomer Ľubor Kresák suggested it was a fragment of Comet Encke, linking it to the Beta Taurid meteor stream, whose activity peaks in late June.

In 1983 Zdeněk Sekanina argued that a fragile comet would have disintegrated much higher in the atmosphere, and that the depth of penetration pointed to a denser, rocky asteroid. In 2001 a statistical study by Farinella and colleagues, which modelled the likely orbits of the incoming body, assigned an 83 per cent probability to an asteroidal origin and 17 per cent to a cometary one. Most researchers now lean toward a stony asteroid, but the question is not closed.

What physical traces have been found?

Researchers have found small traces consistent with an object from space, but no large meteorite. Microscopic silicate and magnetite spheres with high nickel content have been reported in soil and tree resin from the area, which supports an origin in space. In 2013 a team led by Victor Kvasnytsya reported in the journal Planetary and Space Science that samples from peat at the site contained carbon minerals including lonsdaleite, a form of carbon associated with meteorite impacts, and that the material was consistent with an iron meteorite. The interpretation has supporters and critics, so it is best described as a reported finding rather than settled proof.

Lake Cheko, a small lake about 8 kilometres from the centre of the blast, became the focus of a separate debate. In 2007 an Italian team led by Gasperini proposed that it might be a crater formed by a fragment of the object. Collins and Artemieva disputed this in the journal Terra Nova in 2008, arguing that the lake is not an impact crater. A 2017 study by Russian researchers, using annual sediment layers, concluded that the lake is at least about 280 years old, which would make it older than the 1908 event.

A minority hypothesis published in 2020 by Khrennikov and colleagues modelled a different scenario: an iron asteroid that grazed the upper atmosphere at a shallow angle, produced the shock wave, and then flew back out into space. It would explain the missing fragments, but it is a minority view.

How Chelyabinsk helps explain Tunguska

The 2013 Chelyabinsk meteor is the best-recorded airburst in history and a real-world check on Tunguska models. On 15 February 2013 an asteroid roughly 18 metres across and weighing around 11,000 tonnes entered the atmosphere over Russia's Ural region and exploded about 23 kilometres above the ground. NASA's Jet Propulsion Laboratory estimated its total energy at about 440 kilotons of TNT and described it as the most energetic impact event recognised since Tunguska.

The shock wave broke windows across the city and damaged thousands of buildings. More than 1,000 people were injured, mostly by flying glass, and no deaths were reported. Because it was filmed by dashboard cameras and recorded by infrasound and seismic stations, researchers could reconstruct its trajectory and breakup in detail.

Chelyabinsk was smaller and burst much higher, and Tunguska released roughly seven to seventy times more energy depending on the estimate used. But the physics is the same, and the 2013 data has been used to test models of how the 1908 object broke up and how its blast reached the ground.

The fringe theories: spaceships, antimatter, black holes and Tesla

The missing crater and the long gap before anyone reached the site left room for speculation. None of the alternative explanations has physical or documentary support, and they should be read as fringe ideas rather than open scientific questions.

The most famous began as fiction. In 1946 the Soviet writer Alexander Kazantsev published "Explosion", a short story in which a nuclear-powered alien spacecraft blows up over Siberia. The idea of a crashed ship has followed Tunguska ever since, even though no wreckage or other physical evidence of a craft has ever been found.

Some proposals appeared in serious journals before being set aside. In 1965 Clyde Cowan, C. R. Atluri and Willard Libby published a paper in Nature exploring whether the object might have contained antimatter. In 1973 A. A. Jackson and Michael Ryan suggested in Nature that a tiny black hole passing through the Earth could explain the event. The German astrophysicist Wolfgang Kundt later argued that around 10 million tonnes of natural gas escaped from the crust and exploded. None has gained acceptance: the airburst model explains the observations without them, and the evidence each would predict has not turned up.

A popular modern story claims that Nikola Tesla caused the blast with his wireless-power experiments. There is nothing in Tesla's records, correspondence or known equipment to support this, and no apparatus he is known to have built came close to the energy involved. For what Tesla actually built and wrote, as opposed to the legends that have grown around him, see the Nikola Tesla pillar.

Billy Carson's reading

Billy Carson has not published a dedicated talk, article or podcast episode on the Tunguska event, so this article does not attribute any view of it to him. The questions it raises run through subjects his audience follows closely: how objects from space have shaped life on Earth, whether ancient catastrophes were remembered in myth, and how to weigh unconventional explanations against the evidence, themes gathered in the Holographic Universe hub.

Two other airburst debates on the site extend the Tunguska story into the deep past. The Younger Dryas impact hypothesis asks whether a comet or asteroid disrupted the climate and cultures of the late Ice Age, and the Sodom and Gomorrah airburst debate examines the claim that a Tunguska-style blast destroyed Tall el-Hammam in the Jordan Valley. For whether some visitors from space might be more than rocks, the Oumuamua guide covers the first known interstellar object and the artificial-probe argument.

Watch, read and go deeper

The Holographic Universe topic hub gathers Billy Carson's talks and articles on the nature of reality and the cosmos, and is the best starting point for the wider questions behind this article. From there, the Younger Dryas and Sodom and Gomorrah pillars set Tunguska beside other proposed cosmic impacts, while the Oumuamua and Nikola Tesla pillars take up the space-object and Tesla questions the Tunguska legends raise.

Frequently asked questions

What caused the Tunguska event?

The scientific consensus is that a space rock tens of metres across exploded in the atmosphere roughly 5 to 10 kilometres above the Siberian forest on 30 June 1908. The blast flattened about 2,150 square kilometres of trees without leaving a crater. Researchers still debate whether the object was a stony asteroid or a comet fragment, with most leaning toward an asteroid.

Why was no crater or meteorite found at Tunguska?

The object broke apart and released its energy in the air, so no crater formed. Leonid Kulik searched for a crater and an iron meteorite from 1927 onward and found neither; only microscopic particles and mineral traces have since been reported.

How powerful was the Tunguska explosion?

Estimates depend on the model: about 3 to 5 megatons of TNT in 2007 Sandia National Laboratories simulations, 10 to 15 megatons in older estimates, and up to 20 to 30 megatons in some later studies. Any single figure should be treated with caution.

Is Lake Cheko the Tunguska impact crater?

That was proposed by an Italian team in 2007, but the idea is disputed. Collins and Artemieva argued against an impact origin in 2008, and a 2017 study of the lake's sediment layers concluded it is at least about 280 years old, older than the 1908 event.

Could Tunguska happen again?

Yes, though events of this size are rare, with estimates ranging from once every few centuries to once in a thousand years. Smaller airbursts happen more often; the 2013 Chelyabinsk meteor injured more than 1,000 people over a populated area.

Sources and further reading

• Sekanina, Zdeněk. Analysis of the Tunguska body's atmospheric entry, arguing against a comet. The Astronomical Journal, 1983.
• Farinella, Paolo, and colleagues. Statistical study of the orbit and origin of the Tunguska cosmic body. Astronomy and Astrophysics, 2001.
• Collins, Gareth, and Natalia Artemieva. Critique of the Lake Cheko impact-crater proposal. Terra Nova, 2008.
• Kvasnytsya, Victor, and colleagues. Mineral analysis of samples from the Tunguska site. Planetary and Space Science, volume 84, 2013.
• NASA Jet Propulsion Laboratory, Center for Near Earth Object Studies. "Additional Details on the Large Fireball Event over Russia on Feb. 15, 2013."
• Jackson, A. A., and Michael P. Ryan. "Was the Tungus Event due to a Black Hole?" Nature, volume 245, 1973.
• Kazantsev, Alexander. "Explosion" (short story), 1946.