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According to geophysicist Aurélien Dupont of the PusanNational University in South Korea, as gasses percolate throughunderground magma they produce specific low-frequency sounds."By recording and analyzing the sounds emitted by basalticvolcanoes," Dupont said, "volcanologists can useinfrasound to measure the flow and behavior of magma and bettersurvey volcanic activity." He is presenting his research atthe Acoustics 2012 meeting in Hong Kong, May 13-18, a joint meetingof the Acoustical Society of America (ASA), Acoustical Society ofChina, Western Pacific Acoustics Conference, and the Hong KongInstitute of Acoustics. By tracking the main sources of infrasound during the eruptions,the researcher discovered that the gas pockets trapped in the magmadecreased in size throughout the course of the eruption until theydisappeared at the eruption's end. "The gas volume fractionconstantly decreases in the volcanic conduit during a basalticeruption," Dupont said. Basaltic magma has low viscosity and relatively low gas content soit flows easily, producing volcanoes with gentle slopes andimpressive displays like lava fountains and rivers of lava. As the magma travels from the underground magma reservoir to thesurface, the gas that is in suspension begins to expand. Thisexpansion produces distinctive infrasound profiles. Once the magmareaches the surface and is under only atmospheric pressure, the gasis able to bubble away and escape. Dupont made his observations at the Piton de la Fournaise volcanoon Reunion Island, which is in the Indian Ocean. This volcanoerupts often and is a perfect field laboratory to test and adaptnew survey techniques, like infrasonic monitoring. For this research, Dupont used condenser microphones andmicrobarometers to detect the sound produced from the gas flow. Hethen correlated that sound profile with observations of volcanicgasses escaping from vents in and around the crater. "If novolcanic gas escapes anymore from the vents, detections stop andthe eruption is over," he noted. "Infrasound canaccurately characterize the beginning and the end of aneruption." The series of volcanic noises, which were recordedbetween 1992 and 2008, brings new constraints to the functioning ofthe eruptions. "The quantitative analysis of the noise produced by the gasflow allows us not only to understand a natural system as complexas a volcano but allows us also to better monitor it,"concludes Dupont. I am an expert from medical-rehab-equipment.com, while we provides the quality product, such as Electric Mobility Wheelchair , China Mobility Walking Aids, Sports Wheel Chair,and more.
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