Intellectual Merit: This project concerns geodetic and geophysical monitoring of two distinct active volcanoes in the Galapagos Islands to understand magma transport and storage, and the balance between shallow intrusion and eruption, all of which have important implications for volcanic hazards assessment.
GPS observations at Sierra Negra volcano since 2000 showed a dramatic increase in the rate of inflation over the past two years, culminating on April 16, 2005 with inelastic failure of the magma chamber roof along a trapdoor fault, and subsequent eruptions in the Fall. Faulting of the caldera floor may have a profound effect on magma storage and the degassing history of the subcaldera magma reservoir. One hypothesis is that trapdoor faulting relaxes elastic stress related to intrusion and inflation, allowing larger volumes of magma to be stored inside the volcano instead of erupting. Serial measurements of volcanic gas emissions and gravity changes, along with updates to existing GPS networks will provide means to test this hypothesis. The first phase of the project will continue monitoring of deformation at Sierra Negra by maintaining the continuous L1 and L1/L2 GPS network installed in 2002 and conducting a follow-up GPS campaign. The GPS results will be integrated with InSAR measurements in order to take advantage of the spatial coverage of that technique. Simultaneous measurement of volcanic gases emitted from fumaroles will monitor degassing processes in response to volume changes in the shallow magma reservoir. Gravity measurements will provide complementary constraints on volume and mass changes in the reservoir at depth. Results of this study will provide constraints on the material properties of the magma and edifice, geochemical and mechanical changes related to variable rates of chamber filling, and the causes and consequences of edifice failure leading to intrusion or eruption.
Fernandina volcano began erupting on May 13, 2005 from a fissure system located on the southwestern caldera rim. This form of eruptive vent, termed a circumferential fissure, is common to Galapagos shield volcanoes and is thought to be governed by stresses acting within the volcano from both gravitational forces on the slopes and magma chamber inflation. One hypothesis is that circumferential fissures and radial intrusions, which occur on the lower flanks of Galapagos shield volcanoes, coexist as the result of strain field interaction. Interestingly, the previous eruption of Fernandina in 1995 was from a radial eruptive fissure on the southwest flank, immediately below the site of the 2005 eruption. The GPS campaign network installed at Fernandina with prior NSF funding was designed to capture a circumferential event like the one that has just occurred, with a dense array of sites in the vicinity of the eruption. At Fernandina, a post-eruption GPS campaign will be implemented to better understand the strain field and mechanisms of fissure formation.
Broader Impacts: The proposed project will provide collaborative research experience for students and faculty from Ph.D.-granting institutions, undergraduate colleges, and Ecuadorian universities, and in coordination with the Charles Darwin Research Station to continue outreach efforts in educational programs for visitors and local residents.
