Brontides Become Respectable
The mystery of natural detonations (Barisal Guns, mistpouffers, etc.) was probed by several scientific groups following the recent episodes of off-shore booms. This paper by Gold and Soter, from Cornell, would have warmed the heart of Charles Fort, for he made much of natural detonation: or "brontides," as they are termed in the early literature. Gold and Soter review the long history of brontides, noting that brontide activity is often associated with earthquakes, but not always. Natural booming noises, they contend, may be due to eruptions of natural gas. This would square with the rare observations of earthquake lights. Interestingly enough, the recent off-shore detonations were occasionally accompanied by luminous phenomena.
(Gold, Thomas, and Soter, Steven; (Brontides: Natural Explosive Noises," Science, 204:371, 1979.)
Reference. Brontides and other "water guns" are collected in GSD1 in Earthquakes, Tides, Unidentified Sounds. Details on the Catalog volume here.