Swamp Gas: To Be, or Not To Be: That is the Question.



Swamp gas has been known by several names: ignis fatuus, will-o’-the-wisp, corpse candles, jack-o’-lantern, and marsh gas. A multitude of reliable references to and descriptions of this natural phenomenon have been found in prestigious journals such as Nature, Edinburgh Philosophical Journal, and Symons Monthly Meteorological Magazine. Some of these references are global in scope and span the years from the 19th century to modern times.[1]


Characteristically, swamp gas is found in peat bogs, mud flats, marshes, and swamps—wherever stagnant water coincides with the decay of organic matter. The following reference demonstrates a typical observation:


          The water of the marsh is ferruginous, and covered with an iridescent crust. During the day bubbles of air were seen rising from it, and in the night blue flames were observed shooting from and playing over its surface. As I suspected that there was some connection between these flames and the bubbles of air, I marked during the day-time the place where the latter rose up most abundantly, and repaired thither during the night; to my great joy I actually observed bluish-purple flames, and did not hesitate to approach them. On reaching the spot they retired, and I pursued them in vain; all attempts to examine them closely were ineffectual. On another day, in the twilight, I went to the place, where I waited the approach of night; the flames became gradually visible, but redder than formerly, thus showing that they burnt also during the day; I approached nearer and they retired. Convinced that they would return again to their place of origin, when the agitation of the air ceased, I remained stationary and motionless, and observed them again gradually approach. As I could easily reach them, it occurred to me to attempt to light paper by means of them, but for some time I did not succeed in this experiment, which I found was owing to my breathing. I therefore held my face from the flame, and also interposed a piece of cloth as a screen; on doing which I was able to singe paper, which became brown-colored, and covered with a viscous moisture. I next used a narrow slip of paper, and enjoyed the pleasure of seeing it take fire. The gas was evidently flammable, and not a phosphorescent one, as some have maintained. But how do these lights originate?[2]


Indeed, how do they originate? In spite of all the observations made of this natural oddity, it remains a puzzle to science. Assumptions have always been made that methane (CH4), a odorless, colorless, and highly flammable gas, is the primary constituent of swamp gas. In nature, swamp gas results from the breakdown of fats, cellulose, and proteins by anaerobic bacteria (those not requiring oxygen) in mud and sediment on the marsh floor. The gas is lighter than air and will burn with a pale blue or yellow flame. At a stagnant pool, bubbles of swamp gas can be induced to ignite with a lighted match. The gas will burn with a brief flame and often emit a ‘pop’ like report.


Bored with the chemistry yet? Cheer up, it gets worse.


The fabled will-o’-the-wisp and jack-o’-lantern are said to be manifestations of swamp gas. However, since methane does not ignite spontaneously, we suddenly find that this phenomenon of nature has become more phenomenal. Sounds redundant, doesn’t it? Well, it’s not nearly as redundant as using a mystery to explain away other mysteries. So, to account for the will-o’-the-wisp how does the gas ignite to provide the necessary flame? A misconception occasionally stated in chemistry texts and books dealing with these phenomena is that the spontaneous ignition of methane could result from the additional presence of phosphine (PH3) in the swamp gas. Phosphine (phosphorus trihydride), a highly poisonous gas also evolved from waterlogged soils, results from the decay of protein, bone, and other phosphate-bearing matter. Interestingly, pure phosphine is not self-igniting either. In order for it to spontaneously inflame, it must be contaminated with a small amount of phosphorous tetrahydride (P2H4). Recently, however, some of these “given” operating conditions for swamp gas have been challenged in the laboratory. Demonstrations have shown that if the tetrahydride-bearing phosphine is injected into a stream of methane—and if self-ignition occurs—the resultant flame will be a bright green color, accompanied by copious smoke and a distinct odor. Nevertheless, despite these findings, it is generally agreed that jack-o’-lanterns do not produce stinking, green contrails. Accordingly, laboratory experiments devoted to the synthesis of self-igniting swamp gas have, thus far, been unsuccessful. In fact, recent tests using soil/phosphate mixtures have evolved flammable, though not self-igniting gasses. Additionally, in the same series of experiments, vapor phase chromatography (a sensitive analysis technique) failed to detect even part-per-million traces of phosphine in the laboratory samples.[3]


The final analysis of this little chemistry lesson infers that in spite of “established facts” and learned opinions on the subject, much remains unclear about the evolution and characteristics of swamp gas in Nature. Furthermore, if the technicalities are still so vague, then perhaps more reservation should be exercised before swamp gas is assigned as the explanation for so many nocturnal luminous phenomena.




(The above article is an excerpt adapted from Stalking The Mysterious Lights by Michael A. Frizzell &

George F. Walls and was originally published in Pursuit Magazine, Volume 20, Fourth Quarter, 1987)



© 2005 M.A. Frizzell & G.F. Walls -All Rights Reserved.

[1] Corliss, William R. Lightning, Auroras, Nocturnal Lights and Related Luminous Phenomena, The Sourcebook Project: Maryland, 1982, pp. 175-176.

[2] This account took place in Newmark, Germany and was documented in an 1832 edition of the Edinburgh New Philosophical Journal and was recaptured for posterity by William R. Corliss in Lightning, Auroras, Nocturnal Lights and Related Luminous Phenomena , pp. 168, 175.

[3] Chemistry in Britain, “Will-o’-the-Wisp,” A.A. Mills, 16: 69-71, February 1980.