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Gas Emissions
As magma nears the surface its pressure decreases and gases escape.
This process is much like what happens when you open a bottle of fizzy
juice and carbon dioxide escapes. Sulphur dioxide is one of the main
volcanic gases. Sulphur dioxide and visible steam are usually the
first things people notice when they visit an active volcano. The
sulphur dioxide has an unpleasant smell like that of rotten eggs.
Gases released by most volcanoes are difficult to sample and measure
on a regular basis, especially when a volcano becomes active.
At the Soufrière Hills Volcano gas emissions are measured using
a spectrometer. A spectrometer uses the sun as a source of infrared
radiation. This means the spectrometer looks at the sun through the
volcanic plume. From this it can measure the amount of gas in the
atmosphere. Interpreting gas emissions can show variations in sulphur
dioxide levels. This can indicate the magma emission rate and may
provide an early warning for changes in eruptive style. |
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