The 2004–2008 dome-building eruption at Mount St. Helens, Washington: Epilogue

Bulletin of Volcanology
By: , and 

Links

Abstract

The 2004–2008 dome-building eruption at Mount St. Helens ended during winter 2007–2008 at a time when field observations were hampered by persistent bad weather. As a result, recognizing the end of the eruption was challenging—but important for scientists trying to understand how and why long-lived eruptions end and for public officials and land managers responsible for hazards mitigation and access restrictions. In hindsight, the end of the eruption was presaged by a slight increase in seismicity in December 2007 that culminated on January 12–13, 2008, with a burst of more than 500 events, most of which occurred in association with several tremor-like signals and a spasmodic burst of long-period earthquakes. At about the same time, a series of regular, localized, small-amplitude tilt events—thousands of which had been recorded during earlier phases of the eruption—came to an end. Thereafter, seismicity declined to 10–20 events per day until January 27–28, when a spasmodic burst of about 50 volcano-tectonic earthquakes occurred over a span of 3 h. This was followed by a brief return of repetitive “drumbeat” earthquakes that characterized much of the eruption. By January 31, however, seismicity had declined to 1–2 earthquakes per day, a rate similar to pre-eruption levels. We attribute the tilt and seismic observations to convulsive stagnation of a semisolid magma plug in the upper part of the conduit. The upward movement of the plug ceased when the excess driving pressure, which had gradually decreased throughout the eruption as a result of reservoir deflation and increasing overburden from the growing dome, was overcome by increasing friction as a result of cooling and crystallization of the plug.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The 2004–2008 dome-building eruption at Mount St. Helens, Washington: Epilogue
Series title Bulletin of Volcanology
DOI 10.1007/s00445-015-0973-4
Volume 77
Issue 10
Year Published 2015
Language English
Publisher Springer International
Publisher location Berlin, Germany
Contributing office(s) Volcano Science Center
Description Article 89; 17 p.
Country United States
State Washington
Other Geospatial Mount St. Helens
Online Only (Y/N) N
Additional Online Files (Y/N) N