| Popis: |
A small explosive eruption at Masaya volcano on 23 April 2001, in which a number of people were injured, was preceded by a distinct change in plume gas compositions. Open-path Fourier transform infrared spectroscopy (FTS) measurements show that the SO2/HCl molar ratio increased from 1.8 to 4.6 between April 2000 and April/May 2001. The SO2 flux decreased from 11 to 4 kg s-1 over this period. We interpret these changes to be the result of scrubbing of water-soluble magmatic gases by a rejuvenated hydrothermal system. A sequence of M 5 earthquakes with epicentres about 7 km from the volcano occurred in July 2000. These may have altered the fracture permeability close to the magmatic conduit, and caused increased magmatic-hydrothermal interaction, leading eventually to the phreatic explosion in 2001. Continuous FTS measurements at suitable volcanoes could provide useful information in support of eruption prediction and forecasting. © 2003 Elsevier Science B.V.. |
