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16 October 2014
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Gas Emissions
A spectrometerAs 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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