Thursday, May 17, 2012

It has been shown that excessive rainfall has encouraged a dome collapse at a number of volcanoes. However the stability of the individual lava dome should affect the ease at which a rain influenced collapse can happen.

In general, it is not possible to forecast a volcanic eruption with an accuracy that would merit the term "prediction". There have been a few limited successes when the activity at a volcano has consistently followed the same pattern before every eruption. This is not possible at volcanoes like the Soufrière Hills Volcano where the main hazards come from dome instabilities.

Research scientists are working on a variety of techniques and theories which may improve on current capabilities.

There are several different types of volcanic earthquakes. One of these, the volcano-tectonic earthquake, is identical to a tectonic earthquake. Both are generated by sudden slip along pre-existing faults that are subject to stress: either stress generated by the movement of magma or stress generated by the movement of tectonic plates. Volcanic earthquakes are usually much smaller in magnitude than tectonic earthquakes, but the only real distinction is that tectonic earthquakes are not located within a volcanic system.

The other types of volcanic earthquakes, including hybrid and long-period events, rockfalls and tremor are only found at volcanoes.

The potential risks from pyroclastic flows are the main factor limiting access by scientists. As flows can happen at any time without warning on any flank of the Soufrière Hills Volcano, MVO scientists carry out no routine work near the dome or the upper flanks of the volcano. If there is a strong need for a closer approach, it will only be done after a proper risk assessment and will usually require helicopter support.

MVO has established permanent monitoring stations in and around the volcano for the three techniques that form the cornerstones of the MVO's monitoringeffort. Seismic Monitoring is used to detect and locate the small earthquakes that accompany any eruption. Ground Deformation Monitoring uses GPS positioning and other techniques to measure the swelling of the ground that occurs during an eruption. Gas Monitoring is used to estimate the amounts of certain gases being emitted from the volcano, principally Sulphur Dioxide.

Many other techniques are used by the scientists at MVO, some in cooperation with other scientists. Observations of the size and condition of the dome are very important. These are based on satellite radar data and images from optical and thermal cameras, taken both from the helicopter and from fixed ground positions. Sampling and analysis of the volcanic deposits and ash is very important.

 

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