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Three-dimensional geophysical mapping of shallow water saturated altered rocks at Mount Baker, Washington: Implications for slope stability

Journal of Volcanology and Geothermal Research

By:
ORCID iD , ORCID iD , ORCID iD , ORCID iD , and ORCID iD
https://doi.org/10.1016/j.jvolgeores.2018.04.013

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Abstract

Water-saturated hydrothermal alteration reduces the strength of volcanic edifices, increasing the potential for catastrophic sector collapses that can lead to far traveled and destructive debris flows. Intense hydrothermal alteration significantly lowers the resistivity and magnetization of volcanic rock and therefore hydrothermally altered rocks can be identified with helicopter electromagnetic and magnetic measurements. Geophysical models constrained by rock properties and geologic mapping show that intensely altered rock is restricted to two small (500 m diameter), >150 m thick regions around Sherman Crater and Dorr Fumarole Field at Mount Baker, Washington. This distribution of alteration contrasts with much thicker and widespread alteration encompassing the summits of Mounts Adams and Rainier prior to the 5600 year old Osceola collapse, which is most likely due to extreme erosion and the limited duration of summit magmatism at Mount Baker. In addition, the models suggest that the upper ~300 m of rock contains water which could help to lubricate potential debris flows. Slope stability modeling incorporating the geophysically modeled distribution of alteration and water indicates that the most likely and largest (~0.1 km3) collapses are from the east side of Sherman Crater. Alteration at Dorr Fumarole Field raises the collapse hazard there, but not significantly because of its lower slope angles. Geochemistry and analogs from other volcanoes suggest a model for the edifice hydrothermal system.

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Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Three-dimensional geophysical mapping of shallow water saturated altered rocks at Mount Baker, Washington: Implications for slope stability
Series title:
Journal of Volcanology and Geothermal Research
DOI:
10.1016/j.jvolgeores.2018.04.013
Volume:
357
Year Published:
2018
Language:
English
Publisher:
Elsevier
Contributing office(s):
Crustal Geophysics and Geochemistry Science Center
Description:
15 p.
First page:
261
Last page:
275
Country:
United States
State:
Washington
Other Geospatial:
Mount Baker