Long-term changes in quiescent degassing at Mount Baker Volcano, Washington, USA; Evidence for a stalled intrusion in 1975 and connection to a deep magma source
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Abstract
Long-term changes have occurred in the chemistry, isotopic ratios, and emission rates of gas at Mount Baker volcano following a major thermal perturbation in 1975. In mid-1975 a large pulse in sulfur and carbon dioxide output was observed both in emission rates and in fumarole samples. Emission rates of CO2 and H2S were ∼ 950 and 112 t/d, respectively, in 1975; these decreased to ∼ 150 and < 1 t/d by 2007. During the peak of the activity the C/S ratio was the lowest ever observed in the Cascade Range and similar to magmatic signatures observed at other basaltic–andesite volcanoes worldwide. Increases in the C/S ratio and decreases in the CO2/CH4 ratio since 1975 suggest a long steady trend back toward a more hydrothermal gas signature. The helium isotope ratio is very high (> 7 Rc/RA), but has declined slightly since the mid-1970s, and δ13C–CO2 has decreased by ≥ 1‰ over time. Both trends are expected from a gradually crystallizing magma. While other scenarios are investigated, we conclude that magma intruded the mid- to shallow-crust beneath Mount Baker during the thermal awakening of 1975. Since that time, evidence for fresh magma has waned, but the continued emission of CO2 and the presence of a long-term hydrothermal system leads us to suspect some continuing connection between the surface and deep convecting magma.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Long-term changes in quiescent degassing at Mount Baker Volcano, Washington, USA; Evidence for a stalled intrusion in 1975 and connection to a deep magma source |
| Series title | Journal of Volcanology and Geothermal Research |
| DOI | 10.1016/j.jvolgeores.2009.07.006 |
| Volume | 186 |
| Issue | 3-4 |
| Year Published | 2009 |
| Language | English |
| Publisher | Elsevier |
| Contributing office(s) | Volcano Hazards Program, Volcano Science Center |
| Description | 8 p. |
| First page | 379 |
| Last page | 386 |
| Country | United States |
| State | Washington |
| Other Geospatial | Mount Baker Volcano |
| Google Analytic Metrics | Metrics page |