The Tunguska event
On 30 June 1908 an explosion over Siberia flattened about 2,000 square kilometres of forest. No crater and no pieces of the object have ever been found.
The question What flattened 2,000 square kilometres of Siberian forest on 30 June 1908: a meteor, a comet, a UFO, or Tesla?
What the records say
The documented story holds up: 8 of 9 timeline steps are Confirmed by the records (score 97).
4 theories checked: 1 disproven, 2 unverified, 1 disputed. A theory is rated by its key claim.
A NASA workshop’s models converge on a stony asteroid exploding about 10 km up
confirmedCredible: it rests on a primary (tier-1) record. See the step
Down the rabbit hole
The ground line is the documented timeline. Each tunnel is a theory that branches off it; every chamber is a step, coloured by how well the records support it. The deepest chamber is the theory’s key claim. Tap one to open it.
Main timeline
Oldest first- 30 Jun 1908confirmed
An explosion over Siberia flattens forest near the Stony Tunguska River
At about 7:15 am local time, Evenki reindeer herders saw “a fireball trailing smoke, then a flash brighter than the Sun, followed by a loud noise like thunder.” A 2007 peer-reviewed paper puts the destruction at over 2,000 km² of taiga.
- 30 Jun 1908confirmed
Instruments far away record the blast
A seismograph at Irkutsk, about a thousand kilometres south, recorded it, and an air-pressure wave was measured around the world. A 2018 NASA report says the current summary of the pressure-wave and seismic data rests mainly on two good-quality microbarograph records.
T1NASA technical memorandum, Dec 2018pp. 2, 7 - 30 Jun–Jul 1908confirmed
Nights stay unusually bright over northern Europe
The 2018 NASA report lists “light (or white) nights” lasting several nights in northern Europe among the event’s data. Russian modellers link them to a plume of vapour thrown up to about 100 km.
T1NASA technical memorandum, Dec 2018pp. 2–3 - 1926likely
Evenki accounts report that people died
The most reliable reports, gathered at an Evenki meeting in 1926, report 3 casualties; a 2018 NASA report calls the accounts of several deaths “fairly reliable”. The accounts were collected years after the event and the places are only approximately known.
T2Jenniskens et al., Meteoritical Society abstract, 2018“Tunguska eyewitness accounts”T1NASA technical memorandum, Dec 2018p. 3Sources disagreeThe 2018 NASA report places the deaths in nomad camps roughly 25 km from the epicentre; the 2018 abstract by the same research group says 30–50 km. - 1927–1930sconfirmed
Leonid Kulik’s expeditions find a flattened forest but no meteorite
Sent by the Soviet Academy of Sciences, Kulik could not reach the site in 1921 and got there in 1927. Near the epicentre trees still stood, stripped of branches and bark. His expeditions ran into the 1930s.
- 1927 onwardconfirmed
No crater and no pieces of the object are found
The 2018 NASA report: “no fragments of the exploding object have been recovered, perhaps because it fell in a boggy area, and there is no impact crater.”
- 1950s–1960sconfirmed
Surveys map a butterfly-shaped area of fallen trees of about 2,150 km²
Aerial and ground surveys outlined about 830 square miles of destruction, with millions of trees knocked over. The widely repeated “80 million trees” is not a count: a 2025 peer-reviewed comment traces it to a rough 1933 guess based on an area overestimated about fourfold.
T2NASA history article, 30 Jun 2023T1Gasperini et al., Terra Nova, 2007abstractT2Foschini et al., arXiv preprint, 2019p. 1T1Boslough & Bruno, Scientific Reports, 2025section on “eighty million fallen trees”Sources disagreeMany books still say 80 million trees. The 2025 comment calls the figure exaggerated: the 1933 estimate assumed about 8,000 km² of fallen forest. - 15 Feb 2013confirmed
An asteroid bursts over Chelyabinsk, giving scientists a measured comparison
An asteroid about 19 m across exploded over Chelyabinsk, Russia, with the energy of about 500 kilotons of TNT. Science’s editors called it the largest asteroid impact on Earth since 1908. It was not strong enough to knock down trees.
T1Brown et al., Nature, 2013abstractT1Popova et al., Science, 2013editor’s summaryT2NASA Ames feature, 26 Jun 2019 - 16 Jan 2018confirmed
A NASA workshop’s models converge on a stony asteroid exploding about 10 km up
Four computer codes converged on 10–20 megatons released about 10 km above the ground; a stony body like Chelyabinsk’s would have been roughly 50–80 m across. One team excluded a long-period comet, which would need implausibly high strength.
T1NASA technical memorandum, Dec 2018pp. 2, 4–5, 7–8Sources disagreeMark Boslough’s estimate was and remains 3–5 megatons, the low end. NASA’s 2019 summary of the published papers gives 10–30 megatons at 6 to 9 miles up.
Branches
Go down oneA branch is only as strong as its weakest step so far. The count is how many sources back each step.
Lake Cheko is the crater
Is Lake Cheko, inside the blast zone, a crater left by a piece of the object?
- confirmed
2007: researchers propose that Lake Cheko fills an impact crater
The lake lies about 8 km north-north-west of the inferred epicentre. Gasperini and colleagues said its funnel-like bottom and sediments “all suggest that the lake fills an impact crater”, perhaps from a secondary fragment.
T1Gasperini et al., Terra Nova, 2007abstractStartStrength so far:confirmed· 1 source on this step - confirmed
2008: a rebuttal argues it is not a crater, and the proposers reply
Collins and colleagues cited the lake’s un-crater-like shape, no impactor material, and apparently unaffected mature trees close to the lake, and concluded it “is highly unlikely to be an impact crater.” The 2007 authors replied in the same journal, defending an impact origin.
T1Collins et al., Terra Nova, 2008abstractT1Gasperini et al. reply, Terra Nova, 2008abstract= HoldsStrength so far:confirmed· 2 sources on this step - confirmed
2014: a tree-ring study reads the lake’s trees as fitting a 1908 origin
Trees by the lake kept growing vigorously, unlike trees in the forest. The authors call this pattern “consistent with the formation of the lake at the time of TE” (the Tunguska event).
= HoldsStrength so far:confirmed· 1 source on this step - confirmed
2017: sediment dating says the lake is older than 1908
Rogozin and colleagues used caesium-137 and lead-210 profiles and counted sediment layers, concluding “Cheko Lake is significantly older than the 1908 Tunguska Event”. A 2019 preprint co-written by Gasperini replies that these isotopes are not reliable that far back.
= HoldsStrength so far:confirmed· 2 sources on this step - disputed
Key claim: Lake Cheko is a crater from the 1908 object
Peer-reviewed papers are on both sides. Even the 2019 preprint backing the idea says there is “no clear-cut evidence supporting the impact crater hypothesis, no smoking gun”.
T1Gasperini et al., Terra Nova, 2007abstractT1Tree-ring study, Int. J. Astrobiology, 2014abstractT1Collins et al., Terra Nova, 2008abstractT1Rogozin et al., Doklady Earth Sciences, 2017abstractT2Foschini et al., arXiv preprint, 2019p. 4▼ WeakerStrength so far:disputed· 5 sources on this step
Bullshit meter
- No step is Unverified or Disproven.
- Key claim contradicted by tier 1? Partly. Peer-reviewed papers in 2008 and 2017 contradict it, but the proposers’ evidence is also peer-reviewed, so the key step stays Disputed.
Fluff meter: possibly planted
- Can’t be traced to an original record. Absent: traced to peer-reviewed papers.
- First appeared from new or anonymous accounts. Not measured.
- Coordinated identical wording. Not measured.
- Cited source doesn’t exist. Absent.
- Later contradicted. Present: contested by papers in 2008 and 2017.
● present · ○ absent · – not measured. Lists signals only. It never accuses anyone.
Personal interest meter
- The 2019 preprint, that answers the 2017 dating study is co-written by L. Gasperini, lead author of the 2007 crater proposal. T2Foschini et al., arXiv preprint, 2019author list
“Has a documented interest” only, each one sourced. Never an implication of guilt.
Correlation meter
- Chelyabinsk, 15 Feb 2013, is used to calibrate both the NASA 2018 models (main timeline) and the 2019 Lake Cheko fragmentation preprint (Lake Cheko branch). T2Foschini et al., arXiv preprint, 2019p. 1
- Mark Boslough, co-wrote the 2013 Chelyabinsk paper and the 2025 comment on the “80 million trees” figure (both main timeline), and presented at the 2018 NASA workshop. T1Brown et al., Nature, 2013author list
Links to other cases appear once those cases exist.
Who worked on this
This case was assembled by the site from public records. Contributions are not open yet. Nothing here is invented, so the counts are zero.
This is the first published version of the case.
Sources
- T1David Morrison, “Tunguska Workshop: Applying Modern Tools to Understand the 1908 Tunguska Impact”, NASA Technical Memorandum (printed as NASA/TM--220174), NASA Ames Research Center, December 2018. ntrs.nasa.gov · copy read: ntrs.nasa.gov
- T2John Uri, “115 Years Ago: The Tunguska Asteroid Impact Event”, NASA Johnson Space Center, 30 Jun 2023. www.nasa.gov
- T2Kimberly Ennico Smith, “Tunguska Revisited: 111-Year-Old Mystery Impact Inspires New, More Optimistic Asteroid Predictions”, NASA Ames Research Center, 26 Jun 2019. www.nasa.gov
- T1L. Gasperini, F. Alvisi, G. Biasini, E. Bonatti, G. Longo, M. Pipan, M. Ravaioli and R. Serra, “A possible impact crater for the 1908 Tunguska Event”, Terra Nova 19 (4), 245–251 (2007). doi.org · copy read: api.crossref.org
- T1G. S. Collins, N. Artemieva, K. Wünnemann, P. A. Bland, W. U. Reimold and C. Koeberl, “Evidence that Lake Cheko is not an impact crater”, Terra Nova 20 (2), 165–168 (2008). doi.org · copy read: api.crossref.org
- T1L. Gasperini, E. Bonatti and G. Longo, “Lake Cheko and the Tunguska Event: impact or non-impact?”, Terra Nova 20 (2), 169–172 (2008). doi.org · copy read: api.crossref.org
- T1“The Tunguska event and Cheko lake origin: dendrochronological analysis”, International Journal of Astrobiology 14, 345–357 (online 23 Oct 2014). doi.org · copy read: api.crossref.org
- T1D. Y. Rogozin, A. V. Darin, I. A. Kalugin, M. S. Melgunov, A. V. Meydus and A. G. Degermendzhi, “Sedimentation rate in Cheko Lake (Evenkia, Siberia): New evidence on the problem of the 1908 Tunguska Event”, Doklady Earth Sciences 476, 1226–1228 (2017). link.springer.com
- T2L. Foschini, L. Gasperini, C. Stanghellini, R. Serra, A. Polonia and G. Stanghellini, “The atmospheric fragmentation of the 1908 Tunguska Cosmic Body: reconsidering the possibility of a ground impact”, arXiv:1810.07427v2, 11 Feb 2019 (preprint; journal status not checked). arxiv.org · copy read: arxiv.org
- T1A. A. Jackson IV and Michael P. Ryan Jr., “Was the Tungus Event due to a Black Hole?”, Nature 245, 88–89 (14 Sep 1973). www.nature.com
- T1William H. Beasley and Brian A. Tinsley, “Tungus event was not caused by a black hole”, Nature 250, 555–556 (1 Aug 1974). www.nature.com
- T1P. G. Brown et al., “A 500-kiloton airburst over Chelyabinsk and an enhanced hazard from small impactors”, Nature 503, 238–241 (online 6 Nov 2013). www.nature.com
- T1O. P. Popova et al., “Chelyabinsk Airburst, Damage Assessment, Meteorite Recovery, and Characterization”, Science 342, 1069–1073 (29 Nov 2013). doi.org · copy read: api.crossref.org
- T1Mark Boslough and Andy Bruno, “Misunderstandings about the Tunguska event, shock wave physics, and airbursts have resulted in misinterpretations of evidence at Tall el-Hammam”, Scientific Reports 15, 13869 (22 Apr 2025), Matters Arising. www.nature.com
- T2Peter Jenniskens, Olga P. Popova, Dmitry O. Glazachev, Anna P. Kartashova and Elena D. Podobnaya, “Tunguska eyewitness accounts, injuries, and casualties”, 81st Annual Meeting of the Meteoritical Society 2018, abstract 6234 (LPI Contrib. No. 2067). www.hou.usra.edu
- T2Garret McDonald, review of Andy Bruno, “Tunguska: A Siberian Mystery and Its Environmental Legacy” (Cambridge University Press, 2022), H-Environment, H-Net Reviews, December 2022. www.h-net.org
- T3Oliver Nichelson, “Tesla Wireless and the Tunguska Explosion”, copyright 1995, reprinted in Antentop 02-2003 no. 003, pp. 78–86 (the article says it was first published in a different form in 1990). www.antentop.org