ABSTRACT

This is a project that is jointly funded by the National Science Foundation?s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (UKRI/NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own investigators and component of the work.

Volcanic calderas are some of the most awe-inspiring geologic features on earth. Calderas most often form through the withdrawal of magma through eruption and/or intrusion along rift zones, and collapse of the overlying crust. The 2018 eruption of Kilauea volcano, Hawaii was an excellent example of this. In some cases, however, calderas grow through resurgence. Sierra Negra volcano in the Galapagos Islands, is a large basaltic caldera that has grown through resurgence during its last two eruptions. This study will integrate new and existing Global Positioning System (GPS) precise positioning data with seismic data to investigate pre-, co- and post-eruptive processes. This will improve our understanding of the magmatic and volcanic processes that lead to caldera deformation and the processes that potentially trigger volcanic eruptions. Understanding these processes is important for volcanic hazard assessments not only in the Galapagos, but at caldera systems globally, for example, Kilauea volcano, Hawaii. This project will train the next generation of volcano geophysicists, and continue long-standing collaborations between US, UK, and Ecuadorian scientists. This project would not be possible without the partnership with NERC, who has funded the development of the seismic network and data analyses at Sierra Negra volcano.

Sierra Negra volcano, in the Galápagos Islands of Ecuador, is one of the largest basaltic calderas on Earth, measuring 9 km by 7 km. Through investments from the NSF RAPID and NERC Urgency programs, the June 26-August 30, 2018 eruption of Sierra Negra was the first eruption at a Galápagos Islands volcano to be recorded by a local geophysical monitoring network. The resulting data are spectacular. The eruption involved >6.5 m of pre-eruptive inflation, formation of a ~12 km long fissure system on the north flank, ~8.5 m of co-eruptive deflation (one of the largest co-eruptive displacements ever observed without collapse on caldera-bounding ring faults), and ~1.5 m of net uplift (resurgence) on the intra-caldera trapdoor fault system. Hundreds of thousands of earthquakes accompanied the pre- and co-eruptive phases, including inflationary and deflationary intra-caldera ?trapdoor? faulting events up to Mw5.4. The NSFGEO-NERC collaborative scheme is ideally suited to bring together unique, complementary geodetic and seismic observations and sophisticated numerical modeling techniques to address specific questions relating to the behavior of Sierra Negra, the nature of Galápagos volcanism, and important outstanding questions about fundamental volcano deformation and the interaction between a volcanic edifice and magma plumbing system. The exceptional new geodetic and seismic observations from Sierra Negra offer a unique opportunity to investigate the external and internal deformation of a magmatic system at different stages of unrest. It is rare that a volcanic system is monitored well- and long-enough to observe a complete eruptive sequence from pre-eruptive inflation, magma migration and eruption onset, to co-eruptive deflation, and a return to inflation. By linking observations, through modeling, to changes in pressure and stress within the volcanic system, we will be able to probe the magmatic and structural processes that control magma accumulation and withdrawal, and the initiation of eruptive activity.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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