Incremental Caldera Collapse at Kīlauea Volcano Observed in Ground Tilt and High-Rate GPS Data: Implications for the Magmatic System
Abstract
Kīlauea Volcano's 2018 caldera grew by more than 0.8 cubic kilometers in a series of 62 quasi-periodic seconds-long collapse events. Each collapse consisted of meters-scale fault-bounded subsidence of reservoir roof rock, coincident with inflationary (upwards-and-outwards) ground deformation outside of the growing caldera. Observations were recorded in unprecedented detail on a network of 7 tiltmeters and more than 20 high-rate GPS stations and share similarities with collapses at other basaltic volcanoes, suggesting a common physical mechanism. These data are important for understanding the mechanics and geometry of the processes driving collapse and the relation between collapses, magma transport, and eruption.
Collapse events produced caldera-outwards ground displacements exceeding 20 cm at some stations outside of the growing caldera, and were followed by caldera-inwards deformations at quasi-exponentially decaying rates. Average inter-collapse deformation rates remained nearly constant for the last ~2 months of the eruption, suggesting steady average magma evacuation rates from the summit. We jointly invert stacked co-collapse GPS offsets, tilt offsets, and surface volume change (derived from digital elevation models) to estimate source geometry and co-collapse pressure changes. Observations are consistent to first order with step-like pressurization of Kīlauea's shallow magma system due to the intrusion of roof rock into the reservoir during collapses, although the best-fitting geometry differs somewhat from that estimated for the pre-collapse magma reservoir. Collapses were followed by surges in eruption rate, which we relate with estimated summit pressure changes in order to place bounds on the dimensions of the rift zone conduit feeding the eruptive vent. We find that the eruption was sustained by a low excess magma pressure, demonstrating the importance of collapse events in sustaining the eruption and possibly explaining its abrupt cessation in August 2018.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMV006...03A
- Keywords:
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- 7280 Volcano seismology;
- SEISMOLOGY;
- 8414 Eruption mechanisms and flow emplacement;
- VOLCANOLOGY;
- 8419 Volcano monitoring;
- VOLCANOLOGY;
- 8488 Volcanic hazards and risks;
- VOLCANOLOGY