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Pre- and post-eruptive investigations of gas and water samples from Mount St. Helens, Washington, 2002 to 2005: Chapter 25 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

Professional Paper 1750-25

This report is Chapter 25 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006. For more information, see: Professional Paper 1750
By:
, , , and
Edited by:
David R. Sherrod, William E. Scott, and Peter H. Stauffer

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Abstract

Samples of gas and water from thermal springs in Loowit and Step canyons and creeks that drain the crater at Mount St. Helens have been collected since October 2004 to monitor the flux of dissolved magmatic volatiles in the hydrologic system. The changing composition of the waters highlights a trend that began as early as 1994 and includes decreasing SO4 and Cl concentrations and large increases in HCO3 . Geochemical models indicate that mineral sources and sinks are not the main controls on the changing water chemistry, and carbon and helium isotopes indicate that their sources in the gases and waters have remained unchanged during this time. The present-day molar ratios of C, S, and Cl in the springs approximate ratios measured in plume emissions in August 2005 and provide supporting evidence that changes in water chemistry most likely reflect changes in the release rates of sulfur gases, HCl, and CO2 from the magma and a varying degree of efficiency of gas scrubbing by the overlying water. Results from coupled chemical analyses and discharge measurements on the creeks yield an estimate of the dissolved flux of magmatic HCl, SO2 , and CO2 of around 5.2, 4.7, and 22 metric tons per day, respectively.

Geospatial Extents

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Pre- and post-eruptive investigations of gas and water samples from Mount St. Helens, Washington, 2002 to 2005: Chapter 25 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006
Series title:
Professional Paper
Series number:
1750-25
Year Published:
2008
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Volcano Hazards Program
Description:
20 p.
Larger Work Type:
Report
Larger Work Subtype:
USGS Numbered Series
Larger Work Title:
A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006 (Professional Paper 1750)
First page:
523
Last page:
542
Number of Pages:
20
Country:
United States
State:
Washington
Other Geospatial:
Mount St. Helens