The recent development of the SO2 camera is a powerful new tool for volcanologists that allows quantitative imaging of SO2 amounts within volcanic plumes. Such SO2 images are information-rich compared to traditional measurements by COSPEC or compact UV spectrometer systems which measure the equivalent of one pixel in an SO2 image. Furthermore, using time-series of SO2 images, we can examine short- lived events on the order of seconds and quantitatively constrain wind speed, the greatest source of error in flux determination. The new capabilities offered by the SO2 camera herald a major step forward for understanding degassing processes and therefore civil defence. On October 3 and 4, 2006, we performed SO2 imaging measurements at Stromboli volcano, Italy. The SO2 camera was placed on the north-eastern flank of the volcano about 2.4 km from the summit craters and recorded SO2 images with a time-interval of 5.0 seconds on Oct. 3 and 3.2 seconds on Oct. 4, respectively. More than 1500 SO2 plume images were collected. Major variations in SO2 flux were observed over a timescale of a few minutes and several peaks were seen. By relating the major increases of the flux with a movie of the SO2 plume images, we can conclude that the main cause of these variations was strombolian explosions. In the afternoon of Oct. 3, we took the SO2 camera to the summit of the volcano. The aim of the measurements was to quantify the amount of SO2 emitted during a single explosion. The SO2 camera was set up 400 m north of the craters and a single UV band-pass filter (Center wavelength: 310 nm, HWHM 10 nm) was used in the measurements. We obtained more than 600 plume images with time interval between frames of ~2 seconds. By analyzing the SO2 images, we could separate several explosive events from the background quiescent degassing. The amount of SO2 emitted by a single explosion was 15 - 40 kg which corresponds to approximate total gas mass of 350 - 900 kg. Assuming that the gas slug originated from ~75 MPa (as demonstrated by recent FTIR measurements on Stromboli) we may calculate the volume of the slug at that pressure. Using the ideal gas law and assuming a spherical bubble in the conduit, at a pressure of 75 MPa and temperature of 1150°, this gas amount will occupy a sphere with radius 0.8 - 1.1 m.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 8419 Volcano monitoring (7280);
- 8430 Volcanic gases;
- 8485 Remote sensing of volcanoes