What gases are emitted from Puu Oo? From the cracks on the lava flow?
From the eruption on the coast?
Volcanic gases are emitted during eruptions and periods of inactivity.
During an eruption, the gas plume, like that shown in this photograph, is
mostly (80%) water vapor(H2O), with smaller amounts of sulfur dioxide (SO2)
and carbon dioxide(CO2). The plume is above the Puu Oo vent and was
photographed from the Jaggar Museum. Photograph by J.D. Griggs, U.S.
Geological Survey, April 22, 1985.
Volcanic gases at Kilauea are divided into three groups:
H20 CO2 SO2
--- --- ---
Halemaumau (eruption) 37 50 12 volume %
Halemaumau (quiet) 10 79 11
Puu Oo 78 4 15
Note that most of the carbon dioxide (CO2) is removed by degassing at the
summit before transport to the rift. Fresh magma derived directly from
the mantle has high CO2. Volcanic gases from cracks above lava tubes on
the coastal flat tend to be heavily diluted by air. Samples range from
78% to 99.8% air. CO2 is commonly less than 0.1% but has been measured
as high as 2.5% Rare samples contain up to 25% SO2. The C/S values are
nearly constant, supporting summit degassing as a major control on rift
zone gas concentrations. Gas temperatures as high as 640oC have been
measured. Considering all of the above there is very little hazard to
visitors from gases leaving cracks above tubes. However, the steam plume
created by the lava entering the ocean is dangerous. It contains
hydrochloric acid (HCl) (pH = 1-2) and pieces of volcanic glass.
Visitors must stay out of the plume!