Bill Evans, PhD (Former Employee)

Six natural gas manifestions from the upper Tiber Valley at Caprese Michelangela and Pieve S. Stefano (Arezzo) and at Umbertide (Pertugia) localities have been analysed for major, minor, trace gas compositions, as well as for ??13C in CO2 and CH4, ??15N in N2 and 3He/4He isotopic ratios. All gas emissions are CO2-rich (???94%), with N2 contents of 4-5%. Those from Caprese and Pieve S...

Gas manifestations in north-central Italy consist of CO2-rich gases with minor N2-rich emissions and discharge either along with thermal springs or into cold and stagnant waters. 'Cold' gases are prevalently CO2-dominated (> 90%) while gases related to the thermal waters have variable composition: from CO2 > 99.5% to N2 > 90%. The variable composition of 'thermal' gases is caused by...

Fluids associated with the San Andreas and companion faults n central and south-central California have high 3He/4He ratios. The lack of correlation between helium isotopes and fluid chemistry or local geology requires that fluids enter the fault system from the mantle. Mantle fluids passing through the ductile lower crust must enter the brittle fault zone at or near lithostatic...

No abstract available.

No abstract available.

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, earth scientists 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...