Abstract

Time-series sensor data reveal significant short-term and seasonal variations of magmatic CO2 in soil over a 12 month period in 1995–1996 at the largest tree-kill site on Mammoth Mountain, central-eastern California. Short-term variations leading to ground-level soil CO2 concentrations hazardous and lethal to humans were triggered by shallow faulting in the absence of increased seismicity or intrusion, consistent with tapping a reservoir of accumulated CO2, rather than direct magma degassing. Hydrologic processes closely modulated seasonal variations in CO2 concentrations, which rose to 65%–100% in soil gas under winter snowpack and plunged more than 25% in just days as the CO2 dissolved in spring snowmelt. The high efflux of CO2 through the tree-kill soils acts as an open-system CO2 buffer causing infiltration of waters with pH values commonly of <4.2, acid loading of up to 7 keqH+ṁha−1ṁyr−1, mobilization of toxic Al3+, and long-term decline of soil fertility.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.