Bill Evans, PhD (Former Employee)

A major campaign to quantify the magmatic carbon discharge in cold groundwaters around Mammoth Mountain volcano in eastern California was carried out from 1996 to 1999. The total water flow from all sampled cold springs was ??? 1.8 ?? 107 m3/yr draining an area that receives an estimated 2.5 ?? 107 m3/yr of recharge, suggesting that sample coverage of the groundwater system was...

Here we present the helium and carbon isotope results from the initial study of a fluid chemistry-monitoring program started in the summer of 2001 near the South Sister volcano in central Oregon. The Separation Creek area which is several miles due west of the volcano is the locus of strong crustal uplift currently occurring at a rate of 4-5 cm/yr (Wicks, et. al., 2001). Helium [RC/RA =...

An ongoing episode of crustal uplift centered in the Separation Creek drainage of the Three Sisters area, central Oregon Cascades, may result from a magmatic intrusion that began in 1998. An investigation of springs in this drainage in summer 2001 revealed slightly elevated water temperatures and chloride (Cl-) concentrations of up to about 5?C and 20 milligrams per liter (mg/L)...

Evaluation of 14C in tree rings provides a measure of the flux of magmatic CO2 from Mammoth Mountain both before and after 1994 when copious diffuse emissions were first discovered and linked to tree kill. We analyzed the annual rings of trees with two main purposes: (1) to track changes in the magnitude of magmatic CO2 emission over time, and (2) to determine the onset of magmatic CO2...

Diffuse emissions of CO2 are known to be large around some volcanoes and hydrothermal areas. Accumulation-chamber measurements of CO2 flux are increasingly used to estimate the total magmatic or metamorphic CO2 released from such areas. To assess the performance of accumulation chamber systems at fluxes one to three orders of magnitude higher than normally encountered in soil respiration...

Since 1980, scientists have monitored geologic unrest in Long Valley Caldera and at adjacent Mammoth Mountain, California. After a persistent swarm of earthquakes beneath Mammoth Mountain in 1989, geologists discovered that large volumes of carbon dioxide (CO2 ) gas were seeping from beneath this volcano. This gas is killing trees on the mountain and also can be a danger to people. The U...

Shrub mud volcano, one of three mud volcanoes of the Klawasi group in the Copper River Basin, Alaska, has been discharging warm mud and water and CO2?rich gas since 1996. A field visit to Shrub in June 1999 found the general level of hot-spring discharge to be similar, but somewhat more widespread, than in the previous two years. Evidence of recent animal and vegetation deaths from CO2...

18O values establish that waters are predominantly of meteoric origin. The chemical compositions of water and gases are controlled mainly by the ambient rock types, and chemical geothermometry gives reservoir temperatures of 80-150 degrees C indicating shallow to moderate circulation depths of up to 6 km. However, compositions and isotope abundances of noble gases and delta 13C values of...

No abstract available.

No abstract available.

Carbon dioxide and helium with isotopic compositions indicative of a magmatic source ( δ13C = −4.5 to −5‰, 3He/ 4He = 4.5 to 6.7 RA) are discharging at anomalous rates from Mammoth Mountain, on the southwestern rim of the Long Valley caldera in eastern California. The gas is released mainly as diffuse emissions from normal‐temperature soils, but some gas issues from steam vents or leaves...

No abstract available.