Improved constraints on the estimated size and volatile content of the Mount St. Helens magma system from the 2004–2008 history of dome growth and deformation
Article first published online: 20 OCT 2009
Copyright 2009 by the American Geophysical Union.
Geophysical Research Letters
Volume 36, Issue 20, October 2009
How to Cite
2009), Improved constraints on the estimated size and volatile content of the Mount St. Helens magma system from the 2004–2008 history of dome growth and deformation, Geophys. Res. Lett., 36, L20304, doi:10.1029/2009GL039863., , , and (
- Issue published online: 20 OCT 2009
- Article first published online: 20 OCT 2009
- Manuscript Accepted: 16 SEP 2009
- Manuscript Revised: 9 SEP 2009
- Manuscript Received: 14 JUL 2009
- Mount St. Helens;
- lava domes
 The history of dome growth and geodetic deflation during the 2004–2008 Mount St. Helens eruption can be fit to theoretical curves with parameters such as reservoir volume, bubble content, initial overpressure, and magma rheology, here assumed to be Newtonian viscous, with or without a solid plug in the conduit center. Data from 2004–2008 are consistent with eruption from a 10–25 km3 reservoir containing 0.5–2% bubbles, an initial overpressure of 10–20 MPa, and no significant, sustained recharge. During the eruption we used curve fits to project the eruption's final duration and volume. Early projections predicted a final volume only about half of the actual value; but projections increased with each measurement, implying a temporal increase in reservoir volume or compressibility. A simple interpretation is that early effusion was driven by a 5–10 km3, integrated core of fluid magma. This core expanded with time through creep of semi-solid magma and host rock.