A verneshot (named after French author Jules Verne) is a hypothetical volcanic eruption event caused by the buildup of gas deep underneath a craton. Such an event may be forceful enough to launch an extreme amount of material from the crust and mantle into a sub-orbital trajectory.
Connection with mass extinctions
Verneshots have been proposed as a causal mechanism explaining the statistically unlikely contemporaneous occurrence of continental flood basalts, mass extinctions, and "impact signals" (such as planar deformation features, shocked quartz, and iridium anomalies) traditionally considered definitive evidence of hypervelocity impact events.
The verneshot theory suggests that mantle plumes may cause heating and the buildup of carbon dioxide gas underneath continental lithosphere. If continental rifting occurs above this location, an explosive release of the built up gas may occur, potentially sending out a column of crust and mantle into a globally dispersive, super-stratospheric trajectory. It is unclear whether such a column could stay coherent through this process, or whether the force of this process would result in it shattering into much smaller pieces before impacting. The pipe through which the magma and gas had travelled would collapse during this process, sending a shockwave at hypersonic velocity that would deform the surrounding craton.
A verneshot event is likely to be related to nearby continental flood basalt events, which may occur before, during or after the verneshot event. This may help in searching for evidence for the results of verneshot events; however, it is also quite probable that most of such evidence will be buried underneath the basalt flows, making investigation difficult. J. Phipps Morgan and others have suggested that subcircular Bouguer gravity anomalies recognized beneath the Deccan Traps may indicate the presence of verneshot pipes related to the Cretaceous–Paleogene extinction event.
If the Deccan Traps were the location of a verneshot event at the Cretaceous–Paleogene boundary, the strong iridium spike at the Cretaceous–Paleogene boundary could be explained by the iridium-rich nature in volatiles of the Reunion mantle plume, which is currently beneath Piton de la Fournaise, but during the end Cretaceous was located beneath India in the area of the Deccan Traps; the verneshot event could potentially distribute the iridium globally.
Smaller scale Verneshots
Smaller scale verneshot events were proposed by Phipps Morgan and others to be a possible causal mechanism for the intrusion of kimberlite pipes, which propagate along lines of crustal weakness produced by an earlier larger verneshot event.
The site of the 1908 Tunguska event is proposed as a possible location of a recent micro-verneshot or kimberlite event. The site of ground zero in Tunguska is located within the Siberian traps, a large igneous province, formed at the Permo-Triassic boundary and, interestingly, recent work has indicated a circular depression underlying the traps, a direct prediction of the verneshot model. In the verneshot model, the cratonic crust beneath this region would remain as a point of weakness, allowing the intrusion of a kimberlite pipe or, alternatively, a micro-verneshot, degassing from intrusion, resulted in an outpouring of volcanic gas which was then ignited. However the theory is controversial and is simply stated as a possible example.
The micro-verneshot model does not require the ejection of crustal material—only intrusion at depth.
In 1865 Jules Verne's novel From the Earth to the Moon introduced the concept of a ballistic projectile escaping the Earth's gravity, from which Phipps Morgan and others derived the name "Verneshot" in their paper theorizing a connection between extinction events and cratonic gas ejection. This was in the projectile-naming tradition of John Hunter, whose 47 m expanding hydrogen gun, SHARP, is only a precursor to the "Jules Verne Launcher" with a 3,500 m barrel length, which was designed in the early 1990s for first-stage satellite launch.
- Phipps Morgan, J.; Reston, T. J.; Ranero, C. R. (15 January 2004). "Contemporaneous mass extinctions, continental flood basalts, and ‘impact signals’: are mantle plume-induced lithospheric gas explosions the causal link?" (PDF). Earth and Planetary Science Letters 217 (3–4): 263–284. Bibcode:2004E&PSL.217..263P. doi:10.1016/S0012-821X(03)00602-2. Retrieved 30 June 2015. (First submitted 17 April 2003). For an informal introduction see Professor Jason Phipps Morgan's faculty biography at Cornell University from May 2004:
"I became interested in the causes of mass-extinctions, in particular worrying about the 'too-many-coincidences' problem that these periods appear to be associated (if we believe what's published in the mainstream literature) with BOTH extremely rare continental flood basalts and continental rifting, and even rarer 'impact signals' commonly presumed to come from large extraterrestrial bolide impacts. Our recently published Verneshot hypothesis is our best guess on how to explain these coincidences in a self-consistent causal manner."
- Hryanina, L. (1999). "The bouquet of the meteorite craters in the epicentre of Tunguska impact 1908-year" (PDF). Lunar and Planetary Science XXX (Proceedings of the 30th Lunar and Planetary Science Conference, Houston, TX, USA). Retrieved 24 February 2011.
- Charlene Crabb (6 August 1994). "Shooting at the moon". New Scientist. Archived from the original on 30 September 2007. Retrieved 24 February 2011.