Magmatic Gas Composition Reveals the Source Depth of Slug-Driven Strombolian Explosive Activity
Mike Burton,1*
Patrick Allard,1,2
Filippo Muré,1
Alessandro La Spina1,3
Strombolian-type eruptive activity, common at many volcanoes, consists of regular explosions driven by the bursting of gas slugs that rise faster than surrounding magma. Explosion quakes associated with this activity are usually localized at shallow depth; however, where and how slugs actually form remain poorly constrained. We used spectroscopic measurements performed during both quiescent degassing and explosions on Stromboli volcano (Italy) to demonstrate that gas slugs originate from as deep as the volcano-crust interface (
3 kilometers), where both structural discontinuities and differential bubble-rise speed can promote slug coalescence. The observed decoupling between deep slug genesis and shallow (250-meter) explosion quakes may be a common feature of strombolian activity, determined by the geometry of plumbing systems.
1 Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy.
2 Groupe des Sciences de la Terre, Laboratoire Pierre Süe, CNRS-CEA, Gif-sur-Yvette, France.
3 Dipartimento di Chimica e Fisica della Terra ed Applicazioni, Palermo University, Palermo, Italy.
* To whom correspondence should be addressed. E-mail: burton{at}ct.ingv.it
