Abstract
Imaging growing lava domes has remained a great challenge in volcanology due to their inaccessibility and the severe hazard of collapse or explosion. Changes in surface movement, temperature, or lava viscosity are considered crucial data for hazard assessments at active lava domes and thus valuable study targets. Here, we present results from a series of repeated survey flights with both optical and thermal cameras at the Caliente lava dome, part of the Santiaguito complex at Santa Maria volcano, Guatemala, using an Unoccupied Aircraft System (UAS) to create topography data and orthophotos of the lava dome. This enabled us to track pixel-offsets and delineate the 2D displacement field, strain components, extrusion rate, and apparent lava viscosity. We find that the lava dome displays motions on two separate timescales, (i) slow radial expansion and growth of the dome and (ii) a narrow and fast-moving lava extrusion. Both processes also produced distinctive fracture sets detectable with surface motion, and high strain zones associated with thermal anomalies. Our results highlight that motion patterns at lava domes control the structural and thermal architecture, and different timescales should be considered to better characterize surface motions during dome growth to improve the assessment of volcanic hazards.
Highlights
Lava domes are among the most hazardous and unpredictable volcanic features, making safe observations and studies challenging for researchers
Volcanic areas of varying sizes can be surveyed with relative ease, and Structure-from-Motion (SfM) photogrammetry allows for the creation of detailed 3D models and high resolution digital elevation models (DEMs), which may facilitate the identification of cm-scale features of lava flows and other volcanic surfaces[31], as well as precise eruptive volumes[32]
The dome has a near-circular shape with a diameter of ~200 m and occupies an area of approximately 35,000 m2. It is situated within a larger explosion crater created in 201637 and overtops this crater to the southeast, where a ~35 m wide lava flow is advancing down the flank (Figs. 1b, 2)
Summary
Lava domes are among the most hazardous and unpredictable volcanic features, making safe observations and studies challenging for researchers. Surface strain measurements during lava dome growth are rarely considered, but have been previously derived from fixed camera images[28] and can assist in identifying structural features Despite these advances, detailed insights on the growth styles of lava domes, such as internal growth (endogenous) and growth by extrusion of lava (exogenous), are limited and our understanding on the timescales involved are incomplete. On a few lava domes, the high resolution capabilities of UASs have allowed for highly detailed insights into the structure of the fracture network[34] Another UAS study conducted repeated surveys with thermal sensors on board that facilitated the assessment of the thermal inertia of a lava flow[35]. We construct DEMs and orthophotos, trace the motions of pixels and use this data to delineate the 2D deformation field and gain insight on flow velocities, extrusion rates, surface strain, lava viscosity, and temperature anomalies over different time periods
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