Magma degassing and intermittent lava dome growth.
Date of Issue2008
After its 1980 explosive eruption, Mount St Helens developed a lava dome that grew intermittently for several years. Each growth episode was followed by a long repose, suggesting that the magma column above the reservoir was in hydrostatic equilibrium. A mechanism allowing an increasingly thicker dome is proposed. Loading of the crater floor by the dome acts to prevent gas leakage from magma by closing fractures around the volcanic conduit. Fractures get closed down to a depth that increases as the dome grows. Calculations of dome thickness as a function of dome radius are in good agreement with observations. Renewed growth is triggered by the spreading of the dome. Gas retention over a larger depth extent allows smaller magma densities and a taller magma column above the reservoir. According to this model, small domes can in fact promote explosive volcanic conditions and be unstable
Geophysical research letters
© 2008 American Geophysical Union. This paper was published in Geophysical Research Letters and is made available as an electronic reprint (preprint) with permission of American Geophysical Union. The paper can be found at DOI: [http://dx.doi.org/10.1029/2008GL035432]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.