ERUPTION DYNAMICS AT THE ACTIVE SANTIAGUITO DOME INFERRED FROM A MULTIDISCIPLINARY GEOPHYSICAL EXPERIMENT

Santiaguito Dome, which lies in the shadow of its parent volcano, Santa Maria (Guatemala), has been effusing and exploding for more than eight decades. Pyroclastic emissions from the currently active Caliente Vent are characterized by ash and ballistic-rich emissions at least every hour, with vapor plumes that reach a few kilometers above the crater. Such activity is often accompanied by episodic effusion of a dacitic block lava flow, which overtops the shallow 200-m-diameter crater and flows down the flanks of the cone. We are studying the mechanics of this explosive activity with an arsenal of geophysical sensors because of the unparalleled view into the crater from the Santa Maria summit vantage 1200 m above.

Data collected in January 2007 will enable us to provide a thorough assessment of the energy budget for small-magnitude pyroclastic eruptions involving a silica-rich (dacitic) magma. We will use seismic, infrasonic, thermal imaging, gas flux (SO₂) imaging, high speed video, and Doppler radar observations to assess the temporal chronology of an eruption beginning with pre-eruption seismicity (a few seconds to tens of seconds before the eruption onset), followed by subsequent infrasound radiation, and multi-phase material flux out through the vent. We will integrate our data streams with the goal to better understand the location of various elastic energy sources and to provide more insight into the complex geometry of the crater and conduit system. Diverse measurements will be used to assess the kinetic energy and thermal flux with the end goal of using elastic wavefield studies to remotely quantify eruption intensity at this type of potentially hazardous volcano.