Blue, white and pink flashes lit the sky as people hurried outside during the earthquake near Acapulco, Guerrero, on September 7, 2021, local time. Videos spread under the social-media tag “Apocalipsis.” The unsettling scene prompted questions about “earthquake lights,” but the videos alone cannot establish that the flashes were natural lightning or a single physical phenomenon.
What the term describes
The U.S. Geological Survey explains that earthquake lights is a name given to different reported luminous phenomena associated with earthquakes. Scientists disagree about how many observations convincingly establish a natural phenomenon of this kind.
The USGS also notes that some reports have turned out to involve electricity arcing from shaking power lines. A flash close to damaged infrastructure therefore needs a different investigation from a report of light near a fault in an undeveloped area.
The USGS event record identifies a magnitude 7.0 earthquake, dated September 8 in UTC. Initial news coverage described damage, a reported death and people struggling to keep their balance as shaking was felt in Mexico City. Those were early reports, not a final impact assessment.
The USGS describes the disagreement this way: “Geophysicists differ on the extent to which they think that individual reports of unusual lighting near the time and epicenter of an earthquake actually represent EQL. Some doubt that any of the reports constitute solid evidence.” Rock-related electrical mechanisms have been proposed, but naming a possible mechanism does not identify the cause of a particular urban flash. Reuters’ September 2021 report also recalled reports of similar flashes during a destructive Mexican earthquake in 2017. That is a comparison between reported observations, not evidence that either set of lights had a natural earthquake-related cause. The two posts below show both the footage and the reactions it prompted. Their publication dates help place the discussion in September 2021, but a post’s timestamp is not necessarily the time when its video was recorded.
What a viral video leaves out
A short clip may omit the camera’s exact location, the direction it faced, the original recording time and what happened to the local electricity supply. Editing and reposting can remove precisely the details needed to evaluate an explanation.
When reviewing footage, start with the earliest available upload. Look for matching views from other locations and compare the timing with reports from local authorities or utilities. A dramatic caption should not replace those checks. Two recordings showing the same skyline can be particularly useful: a building, hill or shoreline may help establish the camera angles. A bright flash can overwhelm the camera sensor, however, so its apparent size or colour in a compressed clip is a poor basis for identifying its cause. The strongest account brings together the footage, its location and the surrounding events.
A flash is not a forecast
Unexplained light in a video does not establish a dependable method of predicting the next earthquake. It may remain an unresolved observation without supporting any larger claim.
Other unusual lights have different physical settings. Red sprites occur high above thunderstorms, while volcanic lightning is associated with erupting plumes. Putting each image back into its setting is the first step toward understanding it.
Credits and further reading: Reuters.
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