'Earthquake Lights' [ EQL ] are airborne luminosities associated with seismic activity - reports of them go back more than 2000 years.

With the beginning of seismology as a science in the 19th century, many scholars devoted time to reporting luminosities associated with earthquake activity. To name a few, the Irish engineer Robert Mallet, the “founder of seismology”, published a five part catalog entitled “On the Facts of Earthquake Phenomena” (Mallet, 1851, 1852, 1853, 1854, 1855), in which numerous reports on earthquake luminosities can be found. His catalog, first presented to the British Association of Science, covers the years 1606 B.C. to 1842 A.D.. Ignazio Galli, an Italian priest who graduated in Natural Sciences, published in the early 1900s a catalog of 148 seismic events associated with different types of luminosities. His catalog covers the years 89 B.C. to 1910 A.D. and focuses mainly, but not exclusively, on European events (Galli, 1910). Other early researchers on the subject of earthquake lights (EQL) include the work of Taramelli and Mercalli (1888), De Ballore (1913), Terada (1931), Musya (1932), and Montandon (1948)."

Source : Prevalence of Earthquake Lights Associated with Rift Environments ^{[ paywalled ]} Seismological Research Letters, Volume 85, Number 1

The lights are reported to appear while an earthquake is occurring, although there have been sightings of lights before or after earthquakes. The light shapes are described as similar to those of the auroras, with a white to bluish hue, but occasionally they have been reported having a wider colour spectrum. The luminosity is reported to be visible for several seconds, but has also been seen to last for tens of minutes.

There are many fully documented occurrences, including recent photo and video evidence.

The phenomenon has yet to be explained, although there are several theories regarding their origin. The paper cited above, Prevalence of Earthquake Lights Associated with Rift Environments suggests that “tectonic strain theory” (which itself is poorly defined) may be responsible.

Our study has shown that the vast majority of EQL (i.e., 97%) have been observed in the following three tectonic environments: (1) intraplate rifts or grabens; (2) back‐arc or pull‐apart rifts or grabens (or paleorifts) located inland from subduction zones (orogenic settings); and (3) strike‐slip or transform faults, irrespective of the tectonic setting. The common characteristic of these three geological settings appears to be the presence of deeply penetrating subvertical faults, which exact role, passive or active, in phole propagation and EQL formation has yet to be resolved."

[ Source as above ]

Note: In atomic theory, the 'phole' as mentioned above, means 'a lack of electron' or 'positive hole'.

Also see Hessdalen lightsplugin-autotooltip__plain plugin-autotooltip_bigHessdalen lights

The Hessdalen Lights are unexplained airborne lights observed in the Hessdalen valley in rural central Norway. They first appeared in 1981, and at the peak of activity there were around 20 reports each week. Currently, there are fewer events, but the lights have not stopped entirely.

Editor's Note : Much of the literature draws attention to the possible confusion between EQLs, which are an acknowledged geological phenomenon, and reports which claim they are UFOs.