Workflows for Construction of Spatio-Temporal Probabilistic Maps for Volcanic Hazard Assessment

Probabilistic hazard assessments for studying overland pyroclastic flows or atmospheric ash clouds under short timelines of an evolving crisis, require using the best science available unhampered by complicated and slow manual workflows. Although deterministic mathematical models are available, in most cases, parameters and initial conditions for the equations are usually only known within a prescribed range of uncertainty. For the construction of probabilistic hazard assessments, accurate outputs and propagation of the inherent input uncertainty to quantities of interest are needed to estimate necessary probabilities based on numerous runs of the underlying deterministic model. Characterizing the uncertainty in system states due to parametric and input uncertainty, simultaneously, requires using ensemble based methods to explore the full parameter and input spaces. Complex tasks, such as running thousands of instances of a deterministic model with parameter and input uncertainty require a High Performance Computing infrastructure and skilled personnel that may not be readily available to the policy makers responsible for making informed risk mitigation decisions. For efficiency, programming tasks required for executing ensemble simulations need to run in parallel, leading to twin computational challenges of managing large amounts of data and performing CPU intensive processing. The resulting flow of work requires complex sequences of tasks, interactions, and exchanges of data, hence the automatic management of these workflows are essential. Here we discuss a computer infrastructure, methodology and tools which enable scientists and other members of the volcanology research community to develop workflows for construction of probabilistic hazard maps using remotely accessed computing through a web portal.

Geochronology and geochemistry of the Huntington Formation, Olds Ferry terrane, Blue Mountains province, northern U.S. Cordillera: Implications for accreted terrane correlation and assembly

The Olds Ferry terrane is the more inboard of two accreted volcanic arc terranes in the late Paleozoic−early Mesozoic Blue Mountains province of the northern U.S. Cordillera. We present geologic, geochronologic, and geochemical data from the volcano-sedimentary Huntington Formation of the Olds Ferry arc that place the terrane within a firm temporal and tectonomagmatic context, and establish its identity as a fringing arc terrane along the Triassic to Early Jurassic Cordilleran margin. The Huntington Formation is divided into two unconformity-bounded informal members: a Norian (ca. 220 Ma) lower member comprising a sequence of mafic-intermediate volcanics, massive volcaniclastic breccias, and minor carbonates deposited unconformably onto the 237.7 Ma Brownlee pluton and intruded by the 210.0 Ma Iron Mountain pluton; and a Rhaetian through Pleinsbachian (<210−187.0 Ma) upper member composed of massive conglomerates, abundant rhyodacite to rhyolite effusive and pyroclastic flows, and interlayered sandstone turbidites, deposited with angular unconformity onto the lower member. An erosional hiatus and regional tilting produced an angular unconformity separating the Huntington Formation from the overlying basal conglomerates of the late Early to Middle Jurassic Weatherby Formation of the Izee forearc basin transgressive onlap sequence. Huntington Formation volcanic rocks are isotopically enriched relative to depleted mantle and coeval igneous rocks in the outboard Wallowa terrane. A temporal evolution to more radiogenic 87Sr/86Sr ratios (0.7036−0.7057) and εNd values (+5.4 to +3.1) in the upper member volcanics suggests increasing involvement of continental-derived material in their petrogenesis. Precambrian xenocrystic zircons in both lower and upper member volcaniclastic rocks strongly support a proximal location of the Olds Ferry terrane to cratonal North America during much of its history. The chronology and tectonostratigraphic architecture of the Olds Ferry terrane allows its robust correlation to other fringing-arc terranes along the U.S. and Canadian Cordillera.

Seismic velocity structure of Unzen Volcano, Japan, and relationship to the magma ascent route during eruptions in 1990–1995

Subsurface structures may control the migration of magma beneath a volcano. We used high-resolution seismic tomography to image a low- P-wave velocity (Vp) zone beneath Unzen Volcano, Japan, at depths of 3–16 km beneath sea level. The top of this low-Vp zone is located beneath Mt. Fugendake of Unzen volcano, which emitted 0.21 km3 of dacitic magma as lava domes and pyroclastic flows during eruptions in 1990–1995. Based on hypocenter migrations prior to the 1990–1995 eruptions and modeled pressure source locations for recorded crustal deformation, we conclude that the magma for the 1990–1995 eruptions migrated obliquely upward along the top of the low-Vp zone. As tectonic earthquakes occurred above the deeper part of the low-Vp zone, the deep low-Vp zone is interpreted to be a high-temperature region (> 400 °C) overlying the brittle–ductile transition. By further considering Vs and Vp/Vs structures, we suggest that the deeper part of the low-Vp zone constitutes a highly crystalized magma-mush reservoir, and the shallower part a volatile-rich zone.

Tectono-Paleogeographic Impact on the Permian Depositional Environment and Provenance around the Chaiwopu Depression in the Southern Junggar Basin, NW China

The Chaiwopu Depression in the southern Junggar Basin is located between the West Bogda Mountains and the northeastern Tian Shan Mountains in northwest China. The intracontinental basin–mountain system was formed in the Central Asian Orogenic Belt during the Late Paleozoic. The Permian strata around the depression exhibits distinct variations, which provide significant information to understand its tectonic and depositional evolution. This study investigated six outcrop sites using lithological, sedimentological, and geochemical analyses. The representative lithology of the Lower Permian is submarine lava and pyroclastic flows on the northern margins and alluvial deposits near the southern margins. In the Middle Permian sequence, the extensive distribution of alternating shale and silt/sandstone with oil shale and carbonate indicates a lacustrine setting. The sediments are composed of felsic rock-forming minerals derived mainly from island arc settings. The source rock properties correspond to the Carboniferous volcanic terrain of northeastern Tian Shan. The Lower to Middle Permian source-to-sink system occurred in an incipient level of weathering and maturation, a simple recycling process, and arid to semi-arid climatic conditions. The characteristics and changes of the depositional environment and provenance can be understood in terms of implications of tectono-paleogeographic evolution associated with the West Bogda rifting and uplift.

Mt. Etna Paroxysms of February–April 2021 Monitored and Quantified through a Multi-Platform Satellite Observing System

On 16 February 2021, an eruptive paroxysm took place at Mt. Etna (Sicily, Italy), after continuous Strombolian activity recorded at summit craters, which intensified in December 2020. This was the first of 17 short, but violent, eruptive events occurring during February–April 2021, mostly at a time interval of about 2–3 days between each other. The paroxysms produced lava fountains (up to 1000 m high), huge tephra columns (up to 10–11 km above sea level), lava and pyroclastic flows, expanding 2–4 km towards East and South. The last event, which was characterised by about 3 days of almost continuous eruptive activity (30 March–1 April), generated the most lasting lava fountain (8–9 h). During some paroxysms, volcanic ash led to the temporary closure of the Vincenzo Bellini Catania International Airport. Heavy ash falls then affected the areas surrounding the volcano, in some cases reaching zones located hundreds of kilometres away from the eruptive vent. In this study, we investigate the Mt. Etna paroxysms mentioned above through a multi-platform satellite system. Results retrieved from Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS), and Spinning Enhanced Visible and Infrared Imager (SEVIRI), starting from outputs of the Robust Satellite Techniques for Volcanoes (RSTVOLC), indicate that the 17th paroxysm (31 March–1 April) was the most powerful, with values of radiative power estimated around 14 GW. Moreover, by the analysis of SEVIRI data, we found that the 5th and 17th paroxysms were the most energetic. The Multispectral Instrument (MSI) and the Operational Land Imager (OLI), providing shortwave infrared (SWIR) data at 20/30 m spatial resolution, enabled an accurate localisation of active vents and the mapping of the areas inundated by lava flows. In addition, according to the Normalized Hotspot Indices (NHI) tool, the 1st and 3rd paroxysm (18 and 28 February) generated the largest thermal anomaly at Mt. Etna after June 2013, when Landsat-8 OLI data became available. Despite the impact of clouds/plumes, pixel saturation, and other factors (e.g., satellite viewing geometry) on thermal anomaly identification, the used multi-sensor approach allowed us to retrieve quantitative information about the 17 paroxysms occurring at Mt. Etna. This approach could support scientists in better interpreting changes in thermal activity, which could lead to future and more dangerous eruptions.

HazMapper: a global open-source natural hazard mapping application in Google Earth Engine

Modern satellite networks with rapid image acquisition cycles allow for near-real-time imaging of areas impacted by natural hazards such as mass wasting, flooding, and volcanic eruptions. Publicly accessible multi-spectral datasets (e.g., Landsat, Sentinel-2) are particularly helpful in analyzing the spatial extent of disturbances, however, the datasets are large and require intensive processing on high-powered computers by trained analysts. HazMapper is an open-access hazard mapping application developed in Google Earth Engine that allows users to derive map and GIS-based products from Sentinel or Landsat datasets without the time- and cost-intensive resources required for traditional analysis. The first iteration of HazMapper relies on a vegetation-based metric, the relative difference in the normalized difference vegetation index (rdNDVI), to identify areas on the landscape where vegetation was removed following a natural disaster. Because of the vegetation-based metric, the tool is typically not suitable for use in desert or polar regions. HazMapper is not a semi-automated routine but makes rapid and repeatable analysis and visualization feasible for both recent and historical natural disasters. Case studies are included for the identification of landslides and debris flows, wildfires, pyroclastic flows, and lava flow inundation. HazMapper is intended for use by both scientists and non-scientists, such as emergency managers and public safety decision-makers.

Phytoliths as an indicator of change in vegetation related to the huge volcanic eruption at 7.3 ka in the southernmost part of Kyushu, southern Japan

Volcanic eruptions can have a significant influence on adjacent ecosystems; however, little is known about the long-term vegetation change related to eruptions. In this study, we examined phytolith records in paleosols at multiple sites in the southern Kyushu District, Japan, to assess the influence of the Kikai caldera eruption 7300 years ago on vegetation. Our results show the vegetational difference before and after the eruption in the study region. Specifically, in the area where the pyroclastic flows distributed more thickly, the original evergreen forest was replaced by Andropogoneae grasslands after the eruption, which has been dominating the landscape in this area for at least 900 years. By contrast, in areas only mildly affected by pyroclastic flows, despite the temporary replacement of forest by grassland, the forest developed and flourished within several hundreds of years of the eruption. This is because a large amount of pyroclastic flow would have devastated all of the vegetation, whereas smaller amounts would have left some untouched forest sites within refugia. Our findings suggest that the vegetation varied significantly depending on the amount of pyroclastic flow reaching the area, even within the pyroclastic flow distributed region.