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The relationship between fumarole gas composition and eruptive activity at Galeras Volcano, Colombia
 

Summary: The relationship between fumarole gas composition and
eruptive activity at Galeras Volcano, Colombia
Tobias P. Fischer Department of Geology, Arizona State University, Tempe, Arizona 85287-1404
Greg B. Arehart*
Argonne National Laboratory, CMT-205, Argonne, Illinois 60439
Neil C. Sturchio
Stanley N. Williams Department of Geology, Arizona State University, Tempe, Arizona 85287-1404
ABSTRACT
Forecasting volcanic eruptions is critical to the mitigation of hazards for the millions
of people living dangerously close to active volcanoes. Volcanic gases collected over five
years from Galeras Volcano, Colombia, and analyzed for chemical and isotopic composition
show the effects of long-term degassing of the magma body and a gradual decline in sulfur
content of the gases. In contrast, short-term (weeks), sharp variations are the precursors
to explosive eruptions. Selective absorption of magmatic SO2 and HCl due to interaction
with low-temperature geothermal waters allows the gas emissions to become dominated by
CO2. Absorption appears to precede an eruption because magmatic volatiles are slowed or
retained by a sealing carapace, reducing the total flux of volatiles and allowing the hy-
drothermal volatiles to dominate gas emissions. Temporal changes in gas compositions
were correlated with eruptive activity and provide new evidence bearing on the mechanism
of this type of "pneumatic" explosive eruptions.

  

Source: Arehart, Greg B. - Department of Geological Sciences, Mackay School of Mines, University of Nevada, Reno

 

Collections: Geosciences