Geology topics

Terrence M. Gerlach

Publications and source records attributed to Terrence M. Gerlach.

4 recordsLinked to original sources

USGS2008

Emission rates of CO2, SO2, and H2S, scrubbing, and preeruption excess volatiles at Mount St. Helens, 2004-2005

Airborne surveillance of gas emissions began at Mount St. Helens on September 27, 2004. Reconnaissance measurements--SO 2 column abundances and CO 2 , SO 2 , and H 2 S concentrations--showed neither a gas plume downwind of the volcano nor gas sources within the crater. Subsequent measurements taken during the period of unrest before the eruption began on October 1 and for several days after October 1 showed only small point sources of gas within the crater. These sources defined a pattern of scrubbed degassing that evolved from near-zero emissions, to scattered CO 2 -only sources, to growing sources of CO 2 with minor H 2 S and SO 2 , and finally to myriad sources of CO 2 with increasingly SO 2 - dominant sulfur gases. Scrubbing strongly hydrolyzed SO 2 but also affected CO 2 and H 2 S.

Washington↗

USGS2005

Reconnaissance gas measurements on the East Rift Zone of Kilauea Volcano, Hawai'i by Fourier transform infrared spectroscopy

We report the results of a set of measurements of volcanic gases on two small ground level plumes in the vicinity of Pu`u `O`o cone on the middle East Rift Zone (ERZ) of Kilauea volcano, Hawai`i on 15 June 2001 using open-path Fourier transform infrared (FTIR) spectroscopy. The work was carried out as a reconnaissance survey to assess the monitoring and research value of FTIR measurements at this volcano. Despite representing emissions of residual volatiles from lava that has undergone prior degassing, the plumes contained detectable amounts of CO2, CO, SO2, HCl, HF and SiF4. Various processes, including subsurface cooling, condensation of water in the atmospheric plume, oxidation, dissolution in water, and reactions with wall rocks at plume vents affect the abundance of these gases. Low concentrations of volcanic CO2 measured against a high ambient background are not well constrained by FTIR spectroscopy. Although there appear to be some differences between these gases and Pu`u `O`o source gases, ratios of HCl/SO2, HF/SO2 and CO/SO2 determined by FTIR measurements of these two small plumes compare reasonably well with earlier published analyses of ERZ vent samples. The measurements yielded emission rate estimates of 4, 11 and 4 t d-1

Hawaii↗

USGS1998

Rates of volcanic CO 2 degassing from airborne determinations of SO 2 Emission rates and plume CO 2 SO 2 : test study at Pu′u ′O′o Cone, Kilauea Volcano, Hawaii

We present an airborne method that eliminates or minimizes several disadvantages of the customary plume cross-section sampling method for determining volcanic CO 2 emission rates. A LI-COR CO 2 analyzer system (LICOR), a Fourier transform infrared spectrometer system (FTIR), and a correlation spectrometer (COSPEC) were used to constrain the plume CO 2 /SO 2 and the SO 2 emission rate. The method yielded a CO 2 emission rate of 300 td −1 (metric tons per day) for Pu′u ′O′o cone, Kilauea volcano, on 19 September 1995. The CO 2 /SO 2 of 0.20 determined from airborne LICOR and FTIR plume measurements agreed with the CO 2 /SO 2 of 204 ground-based samples collected from vents over a 14-year period since the Pu′u ′O′o eruption began in January 1983.

Geophysical Research Letters↗

USGS1997

Impacts of volcanic gases on climate, the environment, and people

Gases from volcanoes give rise to numerous impacts on climate, the environment, and people. U.S. Geological Survey (USGS) scientists are inventorying gas emissions at many of the almost 70 active volcanoes in the United States. This effort helps build a better understanding of the dynamic processes at work on the Earth's surface and is contributing important new information on how volcanic emissions affect global change.

Open-File Report↗