January Reconnaissance Trip

May/June Expedition

Press Release

TECHNICAL DATA  AND  GAS MEASUREMENTS
 
 

(ABOVE)   Modis-Aster Simulator (MASTER) false -color image of Isla San Luis showing several different  vents and craters.  The image was generated from data  collected on a May 1999 low-altitude overflight of the  area as part of a NASA project for volcanic hazards  assessment.  The red, green, and blue bands in this image are bands 2, 5, and 8, respectively.   These  correspond to wavelengths of 0.498, 0.660, and 0.800 microns.

(ABOVE)   Modis-Aster Simulator (MASTER) false- color image of Isla San Luis showing several different  vents and craters.  The image was generated from data collected on a May 1999 low-altitude overflight of the  area as part of a NASA project for volcanic hazards  assessment.  The red, green, and blue bands in this image are bands 2/13, 5/13, and 8/21, respectively.  Bands 2, 5, 8, 13, and 21 correspond to wavelengths  of 0.498, 0.660, and 0.800, 1.665, and 2.160 microns.

(ABOVE)   Landsat image of the La Reforma caldera (right)  along the Gulf of California coast and the composite volcano of Las Tres Virgenes (left center).  Note the young dark lavas emanating from Tres Virgenes.

(ABOVE)Landsat image of the Las Tres Virgenes volcano (upper right). Note the dark-colored young lavas radiating from Tres Virgenes and the white pumicious La Virgen tephra lobe spread across the landscape to the SW of Tres Virgenes.  The Bonfil fault cuts across the center of the image and strikes NW.

GAS SAMPLING

    Gas sampling will be done to characterize the chemical composition and rates of emission of gases in selected areas.  Magma contains gases from the Earth's interior.  Generally gas makes up about 1 to 4 weight percent of the magma and consists mostly of water vapor, carbon dioxide, and sulfur gases.  As magma rises toward the Earth's surface it decompresses and some of the gas is released.  Gas reaches the surface through vents and fissures or diffusely through permeable rocks and soils of active and inactive volcanoes.  The amount and composition of gases emitted from volcanoes can provide clues to the nature of the magmatic system that supplies a volcano and can be used to help assess the potential for renewed volcanic activity from dormant volcanoes.
 

We will attempt to locate active gas vents reported by boaters around Isla San Luis.  Gas from vents will be collected in evacuated glass flasks.  The flasks will be returned to a laboratory where chemical analyses will be done using a gas chromatograph.  Gas vents are less likely to be found at the older volcano, La Reforma, but there could be diffuse emissions of gas through porous soils or fractured zones.  Diffuse emissions of CO2 will be measured at a number of sites on Isla Luis and at La Reforma.  The measurements will be made using a system consisting of a small chamber with an open bottom set on the ground; the air and any emitted soil gas that collects in the chamber is pumped through an infrared CO2 analyzer and then returned to the chamber.  By recording the rate of increase in CO2 concentration over a period of several minutes, the flux or rate of CO2 emission can be determined.  Many active and dormant volcanoes produce large CO2 fluxes and therefore play an important part in the Earth's carbon cycle.