The Tunguska Event
On the morning of June 30, 1908, an explosion equivalent to roughly 10–15 megatons of TNT flattened approximately 2,150 km² of Siberian taiga near the Stony Tunguska River. No crater was found. The first scientific expedition reached the site nineteen years later. The leading explanation today — a stony asteroid airburst at ~5–10 km altitude — fits most of the physical evidence, though competing hypotheses about composition (cometary, stony, carbonaceous) are still debated.
Our read
Evidence — 10 claims
8 supported · 1 contested · 1 open
Sources — 4
4 sources · academic + secondary
Contested
Competing readings of the record remain live.
- SupportedThe 1908 Tunguska explosion flattened approximately 2,150 km² of Siberian taiga.
- SupportedThe explosion yield is estimated at roughly 10–15 megatons of TNT.
- SupportedNo crater was found at the Tunguska site.
- SupportedLeonid Kulik led the first scientific expedition to the site in 1928, 19 years after the event.
- SupportedKulik documented a radial tree-blowdown pattern centered above the Southern Swamp but found no iron mass.
- SupportedChyba et al. (1993) proposed a stony asteroid ~60 m in diameter airbursting at ~8 km altitude as the cause.
- SupportedBoslough (2008) modeling showed the airburst produced a downward jet concentrating energy at the surface.
- SupportedLongo et al. (2005) recovered microspherules from Lake Cheko with isotopic ratios consistent with extraterrestrial material.
- ContestedLongo et al. proposed Lake Cheko formed from a fragment impact; subsequent research contested this.
- OpenThe exact composition of the Tunguska impactor — stony, cometary, or carbonaceous — remains unresolved.
What remains unexplained
The stony asteroid airburst is the consensus explanation, but the impactor's exact composition is unresolved, no definitive fragment has been recovered, and Lake Cheko's origin remains contested.
- 01No substantial fragment of the Tunguska object has ever been definitively identified or recovered.
- 02Impactor composition — stony, cometary, or carbonaceous — is still debated among researchers.
- 03Lake Cheko's proposed origin as a fragment-impact crater is contested; later research places its formation before 1908.
June 30, 1908. Somewhere above the Stony Tunguska River in central Siberia, something ended. The explosion — estimated at 10–15 megatons — flattened roughly 2,150 km² of taiga, snapped trees like matchsticks in a radial pattern, and was felt hundreds of kilometers away. No crater. No recovered mass. No scientific expedition for nineteen years.
What happened
Witnesses in the region reported a column of bluish light, a flash brighter than the sun, and a shockwave that knocked people off their feet. Seismic stations across Europe registered the event. Atmospheric pressure waves circled the globe twice. Whatever it was, it hit hard and left almost nothing behind.
Leonid Kulik led the first Soviet Academy of Sciences expedition to the site in 1928 — nearly two decades after the event. He found the radial blowdown pattern, thousands of trees pointing away from a central point above what he called the Southern Swamp. He expected to find a buried iron meteorite. He ran four expeditions. He never found one (Leonid Kulik, Soviet Academy of Sciences first Tunguska expedition report, 1928).
The evidence
The physical record is specific and strange in equal measure. The blowdown is real and well-documented. The epicenter is locatable. What's missing is the object itself.
In 1993, Chyba, Thomas, and Zahnle published the modern working hypothesis in Nature: a stony asteroid roughly 60 meters in diameter, entering the atmosphere at high velocity and disintegrating at approximately 8 km altitude. A stony body, unlike an iron one, would fragment and vaporize before reaching the ground — no crater, no recoverable mass, blast pattern consistent with what Kulik documented. The modeling fits. It's the explanation that most researchers work from.
Mark Boslough's 2008 computational modeling at Sandia National Labs refined the picture further, showing that an airburst of this type produces a downward-directed jet that concentrates energy at the surface — which explains why the damage footprint is larger than a simple overhead explosion would predict (Mark Boslough, Sandia National Labs / American Geophysical Union, 2008).
In 2005, an Italian team led by Giuseppe Longo investigated Lake Cheko, a small lake near the epicenter, as a possible fragment-impact site. They recovered microspherules from the lake sediments with isotopic ratios consistent with extraterrestrial material. They proposed Lake Cheko itself formed from a fragment impact. The microremnant findings are accepted; the lake-as-crater hypothesis is contested — subsequent research put the lake's age well before 1908 (Longo et al., Planetary and Space Science, 2005).
What the explanations don't explain
The stony asteroid airburst model is compelling. It's also not fully closed. The exact composition of the impactor — stony, cometary, carbonaceous — is still debated. A cometary body would also leave no crater and no recoverable mass, and some researchers have argued for that interpretation. The microremnant evidence points toward something rocky, but the sample is small and the conclusions are cautious.
Kulik spent years convinced there was a buried iron mass. There wasn't. That's a reminder that confident predictions about Tunguska have a track record of not quite landing.
What's still open
The airburst explanation is the consensus. The composition question is not resolved. Lake Cheko's origin remains debated. No substantial fragment of the Tunguska object has ever been recovered and definitively identified. The largest explosion in recorded human history left behind a forest of fallen trees, some microspherules, and a question the record hasn't fully answered: what, exactly, hit us.
Why was there no crater at Tunguska?
The leading explanation is that the impactor — most likely a stony asteroid around 60 meters across — disintegrated and vaporized in the atmosphere before reaching the ground, releasing its energy as an airburst at roughly 8 km altitude. This type of explosion produces a powerful surface blast without leaving a traditional impact crater. Stony bodies fragment far more easily than iron ones, which is why no crater and no recoverable mass were found.
When did scientists first investigate the Tunguska site?
The first scientific expedition reached the Tunguska site in 1928, nearly nineteen years after the 1908 event. Leonid Kulik of the Soviet Academy of Sciences led the team and documented the radial tree-blowdown pattern centered above what he called the Southern Swamp. Kulik ran four expeditions in total, expecting to find a buried iron meteorite — and never did.
What is the current scientific consensus on what caused the Tunguska explosion?
The modern working hypothesis, established by Chyba, Thomas, and Zahnle in a 1993 Nature paper and supported by subsequent computational modeling, is that a stony asteroid roughly 60 meters in diameter entered the atmosphere and exploded at approximately 8 km altitude. The airburst released energy equivalent to 10–15 megatons of TNT, flattening over 2,000 km² of Siberian forest. The exact composition of the object — stony, cometary, or carbonaceous — remains debated.
Did any fragments of the Tunguska object survive?
No substantial fragment has ever been definitively recovered. A 2005 expedition led by Giuseppe Longo found microspherules in Lake Cheko sediments with isotopic ratios consistent with extraterrestrial material, but these are trace remnants rather than recoverable mass. The team also proposed Lake Cheko as a possible fragment-impact crater, though that hypothesis is contested by subsequent research placing the lake's formation before 1908.
How large was the Tunguska explosion?
The explosion is estimated at roughly 10–15 megatons of TNT — roughly 1,000 times the yield of the atomic bomb dropped on Hiroshima. It flattened approximately 2,150 km² of Siberian taiga and generated atmospheric pressure waves that circled the globe twice. Seismic stations across Europe recorded the event on the morning of June 30, 1908.
Unexplained History
Dyatlov Pass
On the night of February 1, 1959, nine Soviet hikers led by Igor Dyatlov cut their tent open from the inside and fled into a -25°C blizzard on the eastern slope of Kholat Syakhl in the northern Urals. All nine died. Bodies were recovered over four months. Two had skull fractures; one had crushing chest injuries; clothing on three carried traces of radioactivity. The case stayed officially unsolved for sixty years.
1959-02-01
Unexplained History
The Hinterkaifeck Murders
In late March 1922, six people — the Gruber family and their newly arrived maid — were killed with a farm mattock at the isolated Hinterkaifeck farmstead in Bavaria. Strange events preceded the murders, and someone evidently stayed at the farm for days afterward, feeding the livestock. Despite a decades-long investigation, no one was ever charged, and the case remains Germany's most famous unsolved murder.
1922-03-31
Unexplained History
The Mary Celeste
In December 1872 a passing ship found the Mary Celeste sailing the Atlantic alone — seaworthy, stocked with six months of food, and completely empty. Ten people and one lifeboat were gone. A Gibraltar court suspected foul play and could prove none. A century and a half later, the best answer is still a careful guess.
1872-12
Soviet Academy of Sciences (Kulik et al.)
1928–1939
Meteoritic origin — but no crater located, no recovered iron
Kulik's four expeditions confirmed the radial blowdown pattern centered on a point above the Southern Swamp but failed to locate a crater or substantial meteoritic fragments. Kulik continued to expect a buried iron mass; none was found in his lifetime.
Chyba / Thomas / Zahnle (Nature, 1993)
1993-01
Stony asteroid, ~30–80 m diameter, airburst at ~8 km altitude
Computational modeling of atmospheric entry showed that a stony body of approximately 60 m would disintegrate at the altitude required to produce the observed blast pattern without leaving a crater. This is the modern working hypothesis.
Longo expedition (Planetary and Space Science, 2005)
1999–2008
Microremnants consistent with extraterrestrial origin recovered from Lake Cheko sediments
Italian researchers proposed Lake Cheko as a possible fragment-impact crater and recovered microspherules with isotopic ratios consistent with extraterrestrial material. The lake-crater hypothesis is contested; the microremnant findings are accepted but not conclusive about a specific fragment.
- Leonid Kulik, Soviet Academy of Sciences first Tunguska expedition report (1928)[public-domain]
- Christopher Chyba, Paul Thomas, Kevin Zahnle, 'The 1908 Tunguska explosion: atmospheric disruption of a stony asteroid' (Nature, 1993)[fair-use]
- Mark Boslough, 'Computational modeling of the 1908 Tunguska impact' (Sandia National Labs / American Geophysical Union, 2008)[fair-use]
- Giuseppe Longo et al., 'Search for microremnants of the Tunguska Cosmic Body' (Planetary and Space Science, 2005)[fair-use]
This account draws on publicly available sources and historical records. Report a factual error →