Volcanica

Magmatic trees: a method to compare processes between igneous systems

2024-07-17T03:09:50+00:00

This paper presents the motivation, instructions, and applications for a new graphical method to construct ‘magmatic trees’, which summarize the petrologic and geochemical processes that formed a particular igneous rock unit or eruption. The method is motivated by the need to develop new ways to compare and contrast igneous systems to address frontier research questions in volcano science. It is designed to be easily executed with common datasets, compel the integration of different data types, and facilitate cross-disciplinary conversations about the processes that underly these data (e.g. between the volcano remote sensing and petrology communities). There are numerous potential applications of the method, which include, a) motivating process-driven hypotheses, b) examining the frequency of particular magmatic processes within and among volcanic systems, c) building mantle and crustal magmatic processes into event trees for hazard assessment, and d) teaching petrologic methods. For example, constructing magmatic trees for successive eruptions at a volcano or for multiple volcanoes within the same tectonic setting not only helps quantify the probability of individual magmatic processes but leads to addressing higher-level questions, such as what crustal and magma characteristics cause the same set of processes to be repeated in successive eruptions at Mounts Hood, Unzen, Pinatubo, and Soufrière Hills, while different sets characterize magmas erupted at neighboring volcanoes like Mount St. Helens? In addition, one can imagine a future where machine learning removes much of the human error from magmatic process identification, as well as magmatic tree construction, thereby enhancing our ability to identify patterns of magmatic processes.

The radial spreading of volcanic umbrella clouds deduced from satellite measurements

2024-09-13T08:57:13+00:00

Analysis of thermal infrared satellite measurements of umbrella clouds generated by volcanic eruptions suggests that asymptotic gravity current models of the temporal (t) radial (r) spreading (r ~t_f, f < 1) of the umbrella-shaped intrusion do not adequately explain the observations. Umbrella clouds from 13 volcanic eruptions are studied using satellite data that have spatial resolutions of ~4–25 km² and temporal resolutions of 1–60 minutes. The umbrella cloud morphology is evaluated using digital image processing tools in a Lagrangian frame of reference. At the onset of neutral buoyancy, the radial spreading is better explained by a stronger dependence on time of r ~ t, rather than t^2/3, t^3/4, or t^2/9. This flow regime exists on the order of minutes and has not been observed previously in satellite data. This may be of significance as it provides a means to rapidly (within the first 2–3 observations) determine the volumetric eruption rate. A hyperbolic tangent model, r ~ tanh(t) is presented that matches the entire radial spreading time history and has a conserved torus-shaped volume in which the intrusion depth is proportional to sech(t). This model also predicts the observed radial velocities. The data and the model estimates of the volumetric flow rate for the 15 January 2022 Hunga eruption are found to be 3.6–5 × 10¹¹ m³s⁻¹, the largest ever measured.

Offshore evidence for volcanic landslide post Last Glacial Maximum at sub-Antarctic Heard Island, southern Indian Ocean

2024-09-13T08:21:08+00:00

Heard Island, an active sub-Antarctic intraplate volcanic island on the Kerguelen Plateau, is mostly covered by glaciers. The amphitheatre shaped summit of the active volcanic centre, Big Ben (2813 m), has been interpreted to be the product of a significant volcanic landslide. Here we present the first offshore geomorphological and geological evidence supporting a volcanic landslide on Big Ben, including: (1) the seafloor to the southwest of Heard resembling a landslide deposit, covering at least 467 km², (2) the spatial correlation between the onshore landslide scar and the offshore deposit and (3) the consistency in lithologies and compositions of rocks sampled from the deposit with the onshore in situ lithologies. ⁴⁰Ar/³⁹Ar geochronology constrains the maximum age of the volcanic landslide to 18.0 ± 1.4 ka, post the Last Glacial Maximum. Finally, we assess the risk of volcanic landslide at Heard Island in the future.

Eldgjá and Laki: Two large Icelandic fissure eruptions and a historical-critical approach for interdisciplinary researchers working on past nature-induced disasters

2024-10-15T08:57:32+00:00

The integration of archives of societies with archives of nature has led to collaborations between the natural sciences and the humanities. Not all those involved consider these archives equal, which led to some studies featuring explanations promoting nature as the prime agent in history. The field of the history of climate and society is currently experiencing a shift away from monocausal explanations. Cultural factors must be considered and their contribution to disasters must be examined. This paper introduces an easy-to-use step-by-step approach composed of crucial questions that need to be considered to analyze the entanglement of nature and society in relation to nature-induced disasters. The approach was developed by examining two large Icelandic fissure eruptions, Eldgjá (939–940 CE) and Laki (1783–1784 CE). The approach presented in this paper offers increased understanding across disciplinary cultures from the perspective of historians and is intended as a thought-provoking impulse for future studies.

Catastrophic lava flow levee failure: precursors, processes, and implications

2024-05-09T07:05:57+00:00

During an effusive eruption crisis the initial advance of a lava flow is typically the primary focus of model forecasts and hazard management efforts. Flow branching and lateral expansion of lava flows can pose significant dangers within evolving flow fields throughout the duration of an eruption and are an underappreciated hazard. We use field monitoring, infrasound, time lapse imagery, and lidar data collected during the 2018 lower East Rift Zone eruption of Kīlauea (Hawai‘i) to track the origins, progression, and implications of a flow branching event caused by catastrophic levee failure. Our analyses show that surges in effusion rate, rheologic transitions between pāhoehoe and ‘a‘ā flow regimes, slope-breaks, pre-existing topographic highs, and the structure of perched levee walls all played a role in the failure of the levee and subsequent re-routing of the lava flow. Failure of perched lava structures leads to an acutely hazardous situation because lava impounded by the structure can rapidly inundate the landscape. This is the first time a levee failure event has been observed in such detail with numerous monitoring techniques; this unprecedented level of observation provides quantifiable insights into levee failure processes that have important implications for hazard mitigation and an improved understanding of lava flow emplacement dynamics

Plant traits, growth stage, and ash mass load control the vulnerability of potato, corn, and wheat crops to volcanic ashfall

2024-03-06T02:06:38+00:00

Current predictive models of ash impact on crops use ash thickness (or mass load) as the explanatory variable but fail to account for other factors, such as plant traits and growth stage, which also influence impact. We conducted a plot experiment with three common crops (potatoes, corn, and wheat), exposing them to representative ash mass loads (0.5 to 9 kg m⁻² ). We recorded visual impacts on the plants at different intervals and estimated yield loss. Distinct impact mechanisms were identified for each crop, including premature flower abscission, irreversible leaf yellowing, desiccation and senescence, and stalk lodging. Exposure of potato, corn, and wheat plants to ash mass loads >1 kg m⁻² significantly reduced yield, but production quality was largely unaffected. These results were used to develop new vulnerability functions for estimating yield loss in potatoes, corn, and wheat following exposure to an ashfall event.

Graph Neural Network based elastic deformation emulators for magmatic reservoirs of complex geometries

2024-05-23T11:47:43+00:00

Measurements of volcano deformation are increasingly routine, but constraining complex magma reservoir geometries via inversions of surface deformation measurements remains challenging. This is partly due to deformation modeling being limited to one of two approaches: computationally efficient semi-analytical elastic solutions for simple magma reservoir geometries (point sources, spheroids, and cracks) and computationally expensive numerical solutions for complex 3D geometries. Here, we introduce a pair of Graph Neural Network (GNN) based elasto-static emulators capable of making fast and reasonably accurate predictions (error upper bound: 15 %) of surface deformation associated with 3D reservoir geometries: a spheroid emulator and a general shape emulator, the latter parameterized with spherical harmonics. The emulators are trained on, and benchmarked against, boundary element (BEM) simulations, providing up to three orders of magnitude speed up compared to BEM methods. Once trained, the emulators can generalize to new reservoir geometries statistically similar to those in the training data set, thus avoiding the need for re-training, a common limitation for existing neural network emulators. We demonstrate the utility of the emulators via Bayesian Markov Chain Monte Carlo inversions of synthetic surface deformation data, showcasing scenarios in which the emulators can, and can not, resolve complex magma reservoir geometries from surface deformation. Our work demonstrates that GNN based emulators have the potential to significantly reduce the computational cost of inverse analyses related to volcano deformation, thereby bringing new insights into the complex geometries of magmatic systems.

Textural complexity and geochemistry of the last millennium pyroclastic deposits from Puyehue-Cordón Caulle Volcanic Complex

2024-09-24T15:10:26+00:00

The component variability in Puyehue-Cordón Caulle Volcanic Complex (PCCVC) products reflects the inherent complexity of volcanic processes. We examine pyroclastic deposits from Cordón Caulle (2011 and 1960 eruptions) and Puyehue (MH tephra) in a profile ∼20 km windward of the PCCVC. All levels have comparable components (pumice, scoria, glass shards, crystals), but their proportions vary according to the dominant eruptive style in both vent sources. The particle microtextures combined with mineralogy and geochemistry differentiate juvenile from non-juvenile particles in macroscopically undifferentiated components, questioning prior assumptions. Highly vesicular pumice is the dominant juvenile component indicating decompression-driven gas exsolution processes. Juvenile blocky glass shards/obsidians, frequently associated with lithics, now provide insights into the potential higher involvement of magma in the phreatomagmatic phases of the MH deposit. Nevertheless, the variability of tephra components is a characteristic of the PCCVC, regardless of the juvenile or lithic character. This research refines tephrochronological tools and deepens our understanding of volcanic processes and deposits in the PCCVC.