Open AccessInvestigation into magma degassing at Nyiragongo volcano, Democratic Republic of the Congo
Author(s) -
Sawyer G. M.,
Carn S. A.,
Tsanev V. I.,
Oppenheimer C.,
Burton M.
Publication year - 2008
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2007gc001829
Subject(s) - geology , lava , magma , volcano , impact crater , strombolian eruption , plume , flux (metallurgy) , mineralogy , geochemistry , atmospheric sciences , astrobiology , materials science , meteorology , physics , metallurgy
We report the first combined measurements of the composition and flux of gas emitted from Nyiragongo volcano by ground‐based remote‐sensing techniques. Ultraviolet spectroscopic measurements made in May/June 2005 and January 2006 indicate average SO 2 emission rates of 38 kg s −1 and 23 kg s −1 , respectively. Open‐path Fourier transform infrared spectroscopic measurements obtained in May/June 2005, January 2006, and June 2007 indicate average molar proportions of 70, 24, 4.6, 0.87, 0.26, 0.11, and 0.0016% for H 2 O, CO 2 , SO 2 , CO, HCl, HF, and OCS, respectively. The composition of the plume was remarkably similar in 2005, 2006, and 2007, with little temporal variation in proportions of CO 2 , SO 2 , and CO, in particular, on the scale of seconds or days or even between the three field campaigns that span a period of 24 months. This stability persisted despite a wide range of degassing behaviors on the surface of the summit crater's lava lake (including discrete strombolian bursts and lava fountains) and variations in the SO 2 emission rate. We explain these observations by a regime of steady state degassing in which bubbles nucleate and ascend in chemical equilibrium with the convecting magma. Short‐term (seconds to minutes) temporal fluctuations in the SO 2 –HCl–HF composition were observed, and these are attributed to shallow degassing processes.