We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Spectroscopic evidence for a lava fountain driven by previously accumulated magmatic gas.
- Authors
Allard, Patrick; Burton, Mike; Muré, Filippo
- Abstract
Lava fountains are spectacular continuous gas jets, propelling lava fragments to heights of several hundred metres, which occasionally occur during eruptions of low-viscosity magmas. Whether they are generated by the effervescent disruption of fast-rising bubbly melt or by the separate ascent of a bubble foam layer accumulated at depth still remains a matter of debate. No field measurement has yet allowed firm discrimination between these two models. A key insight into the origin of lava fountains may be gained by measuring the chemical composition of the driving gas phase. This composition should differ markedly depending on whether the magma degassing occurs before or during eruption. Here we report the analysis of magmatic gas during a powerful (250-600?m high) lava fountain, measured with Fourier transform infrared spectroscopy on Mount Etna, Sicily. The abundances of volcanic gas species, determined from absorption spectra of lava radiation, reveal a fountain gas having higher CO2/S and S/Cl ratios than other etnean emissions, and which cannot derive from syn-eruptive bulk degassing of Etna basalt. Instead, its composition suggests violent emptying of a gas bubble layer previously accumulated at about 1.5?km depth below the erupting crater.
- Subjects
LAVA; INFRARED spectroscopy; VOLCANIC ash, tuff, etc.; VOLCANIC soils; POISONOUS gases; FOURIER transform infrared spectroscopy
- Publication
Nature, 2005, Vol 433, Issue 7024, p407
- ISSN
0028-0836
- Publication type
Letter
- DOI
10.1038/nature03246