What Causes Skyquakes, the Mystery Booms Heard Around the World?

Background

Reports of loud, unexplained, cannon-like booms with no visible source have circulated for centuries across widely separated parts of the world, each region developing its own local name for the phenomenon long before anyone attempted a scientific study of it. In upstate New York, the sounds reported around Seneca Lake and Cayuga Lake became known as the Seneca Guns, a name that traces to American novelist James Fenimore Cooper, whose family published an account around 1850 describing "a sound resembling the explosion of a heavy piece of artillery, that can be accounted for by none of the known laws of nature." In Bangladesh, British civil servant Henry Beveridge documented similar reports from the Barisal region in his 1876 book on the district's history, giving rise to the name Barisal Guns. Japan has uminari, literally "cries from the sea," while coastal Belgium and the Netherlands call the phenomenon mistpoeffers.

For most of this history, investigation was limited to collecting witness testimony, since no instrument network existed capable of distinguishing a genuine unexplained atmospheric sound from a covered military exercise, a distant quarry blast, an aircraft's sonic boom, or simple storm thunder misheard at a distance. That changed with the deployment of the EarthScope Transportable Array, a large mobile network of seismographs and, at many stations, co-located infrasound sensors, low-frequency acoustic detectors capable of registering sound well below the range of human hearing, that swept across the continental United States over roughly a decade, temporarily blanketing each region it passed through with dense scientific instrumentation.

Main Theories

The atmospheric-infrasound explanation

In 2020, a research team at the University of North Carolina at Chapel Hill, including undergraduate researcher Eli Bird, used EarthScope Transportable Array data recorded near Wilmington and Cape Fear, North Carolina, between 2013 and 2015 to test reported skyquakes against actual instrument recordings. The researchers assembled a catalogue of local mystery-boom reports from news coverage and compared them against the array's data. At two stations near Carolina Beach, they identified genuine short infrasound signals, lasting roughly one to ten seconds, that matched reported boom times. Critically, they found no corresponding seismic activity, no recorded ground shaking, coincided with these signals, allowing them to rule out small, unfelt earthquakes as the source. Presenting their findings at the American Geophysical Union's 2020 annual meeting, the team concluded the booms were atmospheric rather than seismic in origin, most likely explained by some combination of atmospheric pressure changes, temperature-layer effects, and long-distance sound propagation carrying a source's noise unusually far and loud, without identifying a single confirmed originating event for any specific recorded boom.

This explanation's strength is that it is the first skyquake finding grounded in direct instrumental measurement rather than witness testimony alone, and it successfully eliminated the two most commonly proposed conventional explanations for at least the North Carolina cases examined: covert seismic activity and, implicitly, a purely subjective or exaggerated auditory experience, since real acoustic signals were objectively recorded. Its limitation is what it does not do: identifying that a sound is atmospheric in nature is a different and much narrower claim than identifying its specific source, and the study did not, and did not claim to, resolve what atmospheric process or object actually produced the recorded infrasound bursts.

Conventional mundane explanations

Investigators researching individual skyquake reports worldwide routinely identify a large share as conventional events misidentified or misreported: distant thunder from a storm cell too far away to see, sonic booms from military supersonic flights, especially historically before many countries restricted supersonic flight over populated areas, quarry or construction blasting, meteor airbursts, called bolides, exploding audibly in the upper atmosphere, and, in coastal or lakeside locations, ice quakes, the sudden cracking of thick lake or sea ice under thermal stress, which can produce a startlingly loud, gunshot-like report. Sceptical researchers such as Sharon Hill, who has catalogued mystery-boom reports for decades, argue that once these mundane sources are systematically checked against flight records, blasting permits, and weather data, the great majority of reported skyquakes resolve into one of these ordinary categories, leaving only a genuinely small residue of cases, like the North Carolina infrasound detections, that resist straightforward identification.

Common Misconceptions

A common misconception holds that skyquakes are a single, unified phenomenon with one underlying cause waiting to be discovered. The historical and geographic record instead suggests "skyquake" functions as a catch-all label applied to any unexplained boom, encompassing what are very likely several distinct causes, atmospheric acoustics, unidentified meteors, ice cracking, and simple misidentification of ordinary sources among them, rather than evidence of one single unrecognised physical mechanism operating worldwide.

A second misconception treats the 2020 North Carolina study as having "solved" the mystery of skyquakes generally. The study addressed a specific, geographically limited set of reports using data available only where the EarthScope array happened to be deployed at the time; it neither claims, nor could reasonably claim, to explain every historically reported Seneca Gun, Barisal Gun, or mistpoeffer sighting across multiple continents and three centuries of testimony.

Current Consensus

The best available scientific evidence, from the 2020 University of North Carolina infrasound study, indicates that at least some genuinely reported skyquakes are real atmospheric acoustic events rather than misperception, exaggeration, or unfelt seismic activity, while stopping well short of identifying a specific physical source or mechanism for those events. Outside that narrow, instrumentally confirmed set of cases, most researchers regard the broader historical skyquake phenomenon as most likely a mixture of several distinct, individually mundane causes, aggregated under a single popular label because they share a superficial acoustic signature, a loud, unexplained, cannon-like boom, rather than because they share a single common cause.

Why This Mystery Endures

Skyquakes endure partly because they sit in an unusually persistent evidentiary gap: unlike a single dramatic event that can be investigated once and closed, they are a centuries-old, worldwide, recurring pattern that produces new individual reports faster than any research programme could systematically instrument and verify. The 2020 North Carolina study is a rare exception precisely because a dense scientific sensor network happened to already be recording the right region at the right time for an unrelated seismological purpose, a stroke of infrastructure luck unlikely to repeat for most of the world's skyquake-prone regions any time soon.

The phenomenon also endures because it belongs to a small family of unexplained-sound cases this site covers that occupy the same peculiar middle ground between confirmed reality and confirmed cause. The Hum, a persistent low-frequency drone reported by a minority of listeners in specific locations worldwide, and the Bloop, the powerful 1997 oceanic sound NOAA hydrophones recorded and later attributed to icequakes, both share skyquakes' basic shape: a real, instrumentally or widely corroborated acoustic phenomenon whose precise generating mechanism remains only partially resolved, if at all. That combination, genuine data resisting a tidy final explanation, is precisely what keeps each of these cases in circulation long after a single mundane misidentification would have quietly faded from public attention.