Search

Recent developments in low-cost structure-from-motion (SfM) technologies offer new opportunities for geoscientists to acquire high-resolution soil microtopography data at a fraction of the cost of conventional techniques. However, these new methodologies often lack easily accessible error metrics and hence are difficult to evaluate. In this research, a framework was developed to evaluate a SfM approach for soil microtopography measurement through assessment of uncertainty sources and quantification of their potential impact on overall 3D reconstruction. Standard deviations of camera interior orientation parameters estimated from SfM self-calibration within five different soil surface models were several orders of magnitude larger than precisions expected from pattern-based camera calibration. Sensitivity analysis identified the principal point position as the dominant source of calibration-induced uncertainty. Overall, surface elevation values estimated from both technologies were similar in magnitude with a root mean square ( RMS) of elevation difference of 0·2 mm. Nevertheless, the presence of deformation in either SfM or traditional photogrammetric point clouds highlights the importance of quality assurance safeguards (such as a judicious choice of control points) in SfM workflows for soil microtopography applications. [ABSTRACT FROM AUTHOR]

The deformation style of active volcanoes can provide insight into the structural evolution of their edifices, volcanic activity and associated hazards. The Somma‐Vesuvius volcano is considered one of the most dangerous on the planet due to its proximity to the megacity of Naples (Southern Italy). Thus, understanding its deformation style and corresponding long‐term structural evolution are critical aspects for risk reduction. Although a large amount of data has already been collected about Somma‐Vesuvius, the deformation style affecting its volcanic edifice is still debated. Therefore, we devised an integrated approach to clarify the current state of deformation of this volcano. In particular, we combined analog experiments and finite element (FE) modeling to constrain the current deformation style affecting Somma‐Vesuvius and determine the physical parameters controlling its structural evolution. The analog models were built at a scale of 1:100,000 using sand mixtures (brittle analog) and polydimethylsiloxane (ductile analog). The FE models were implemented by considering a three‐dimensional time‐dependent fluid‐dynamic approach performed at both the analog model scale (1:100,000) and actual volcano scale (1:1). We obtained an FE model and a corresponding analog one that faithfully reproduced the observed deformation velocity patterns revealed by differential interferometric synthetic aperture radar (DInSAR) and GPS measurements at Somma‐Vesuvius. Overall, our results support the hypothesis that a combined gravitational spreading‐sagging process governs the deformation style of Somma‐Vesuvius. Plain Language Summary: Volcanic edifices of sufficient mass are capable of deforming substrata under their own weight; this deformation in turn can deform the volcanic edifices themselves. Identifying the deformation style characterizing a volcanic edifice is useful when considering the evolution of its volcanic activity. Vesuvius is considered one of the most dangerous volcanoes on the planet due to its proximity to the megacity of Naples (Southern Italy). Thus, understanding its deformation style and corresponding structural evolution are critical aspects for risk reduction. In order to analyze the deformation process of Vesuvius we used two different modeling techniques: analog modeling and Finite Element numerical modeling. The analog modeling approach allows us to reproduce real processes by using scaled models and media considered analog to natural materials under a physical point of view. The combination of analog and numerical modeling allowed us to constrain the current deformation style affecting Somma‐Vesuvius and to determine the physical parameters controlling its structural evolution. Finally, we compared our results with the observed deformation velocity patterns revealed by Differential Interferometric Synthetic Aperture Radar and GPS measurements at Vesuvius. Overall, the results support the hypothesis that a combined gravitational spreading‐sagging process governs the deformation style of Somma‐Vesuvius. Key Points: Analog and numerical modeling highlighted an active spreading‐sagging process at the Somma‐Vesuvius volcanoA comparison of models with differential interferometric synthetic aperture radar (DInSAR) deformation data validated the modeling proceduresThe spreading process affecting the Vesuvius volcano allowed inferring about the near‐future eruption style [ABSTRACT FROM AUTHOR]

We present the evolution over 3 months of a 2016–2017 pāhoehoe flow at Kīlauea as it changed from a narrow sheet flow into a compound lava field fed by a stable system of tubes. The portion of the flow located on Kīlauea's coastal plain was characterized using helicopter‐based visible and thermal structure‐from‐motion photogrammetry to construct a series of georeferenced digital surface models and thermal maps on eight different days. Results reveal key influences on the emplacement and evolution of such long‐lived pāhoehoe flows. This region of the flow grew by ~12 × 106 m3 with a near‐constant time‐average discharge rate of 1.2–2.7 m3/s. The development of two tube systems is captured and shows an initial nascent tube enhanced by a narrow topographic confinement, which later inflated and created a topographic inversion that modulated the emplacement of a second flow lobe with its own tube system. The analysis of breakouts at various stages of the field's life suggests that the evolution of the thermal and morphological properties of the flow surface reflect its maturity. Thermal properties of breakouts were used to expand the empirical relationship of breakout cooling to longer timescales. This study contributes to the long‐term development and validation of more accurate predictive models for pāhoehoe, required during the management of long‐lasting lava flow crises in Hawai'i and elsewhere. Key Points: We document the first 3 months of a pāhoehoe flow, from its initial crust‐free channel into a compound field fed by a tube systemVisible and thermal aerial images describe the evolution of the morphology and surface temperature of the flow at various datesResults capture the relationship with topography and the partitioning of lava between the flow front, lateral breakouts, and flow inflation [ABSTRACT FROM AUTHOR]