Volcanic Phenomena Research Articles

Quantitative Assessment of Volcanic Thermal Activity from Space Using an Isolation Forest Machine Learning Algorithm

Understanding the dynamics of volcanic activity is crucial for volcano observatories in their efforts to forecast volcanic hazards. Satellite imager data hold promise in offering crucial insights into the thermal behavior of active volcanoes worldwide, facilitating the assessment of volcanic activity levels and identifying significant changes during periods of volcano unrest. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, aboard NASA’s Terra and Aqua satellites, provides invaluable data with high temporal and spectral resolution, enabling comprehensive thermal monitoring of eruptive activity. The accuracy of volcanic activity characterization depends on the quality of models used to relate the relationship between volcanic phenomena and target variables such as temperature. Under these circumstances, machine learning (ML) techniques such as decision trees can be employed to develop reliable models without necessarily offering any particular or explicit insights. Here, we present a ML approach for quantifying volcanic thermal activity levels in near real time using thermal infrared satellite data. We develop an unsupervised Isolation Forest machine learning algorithm, fully implemented in Google Colab using Google Earth Engine (GEE) which utilizes MODIS Land Surface Temperature (LST) data to automatically retrieve information on the thermal state of volcanoes. We evaluate the algorithm on various volcanoes worldwide characterized by different levels of volcanic activity.

AN OVERVIEW OF THE DEVELOPMENT OF STRATIGRAPHY IN ITALY DURING THE 17TH AND 18TH CENTURIES: FROM STENO TO ARDUINO

ABSTRACT The great variety of lithological, stratigraphical and structural features (particularly in mountain areas), as well as volcanoes and sub–volcanic phenomena, attracted many travelling scientists to the Italian peninsula since the 17th century. The description of the Earth's strata became an important issue of the naturalistic research after the works by Niels Steensen (Steno). From the end of the 17th century until the end of the 18th century lithostratigraphical research developed in Italy within the studies and fieldwork of remarkable scientists, such as Antonio Vallisneri, Luigi Ferdinando Marsili, Giovanni Arduino and others. The emergence of stratigraphy, as a significant part of the new science of geology, was later supported by the work of several Italian scientists and geological institutions from the 19th to the 20th century.

THEORIES OF THE EARTH AND ‘PLUTONISM’ IN THE INTRODUZIONE ALLA GEOLOGIA BY THE ITALIAN GEOLOGIST SCIPIONE BREISLAK (1811)

ABSTRACT Scipione Breislak may be considered as one of the most renowned Italian ‘Plutonists’ at the end of the eighteenth and beginning of the nineteenth centuries. In the 1790s, he was a professor of Physics at the Military Academy of Nunziatella in Naples, where he also devoted himself to the study of Vesuvius and the Phlegraean Fields. Thus, he acquainted himself with volcanic phenomena. Breislak's works about the volcanic fields of Campania (Southern Italy) disclosed how Torbern Olof Bergman's theories and Antoine-Laurent de Lavoisier's chemistry had affected his belief in the idea that volcanic eruptions were triggered by ignition of petroleum deposits. After a voluntary exile in France, owing to the downfall of the Roman Republic, Breislak returned to Italy and settled in Milan, where he was appointed as an Inspector of Gunpowder in 1802. Due to his new administrative duties, he had the opportunity to continue studying mineralogy and geology, focusing primarily on the stratigraphy of Lombardy and of the Alps. During the ‘Milanese period’, he published the Introduzione alla geologia (Introduction to geology, 1811), which may be regarded as the first Italian handbook about the ‘new’ science of Geology. In the monograph, he also drew on Huttonian ideas in order to describe the lithostratigraphic features of crystalline rocks. Without neglecting Breislak's volcanological hypotheses, this paper aims to analyze the influence that nineteenth-century Plutonist (Huttonian) geological theories had on the Earth's history that he depicted in the Introduzione alla geologia. The influence of Plutonism—a term that Richard Kirwan introduced to define James Hutton's geological system—may also be recognized in Breislak's rejection of transition rocks. Indeed, according to him: “nature does not make passages or transitions, and each of its products has a specific and particular way to exist” (Breislak 1811, volume 1, pp. 308–309).

Effects of the volcano eruptions on human health

Millions of people are exposed to harmful emissions of gases, vapors, and other inorganic particles during and after volcanic eruptions. These gases have potential short- and long-term effects on human health, particularly on respiratory, ophtalmic, mental systems, as well as on the skin, among others. It has also been described that volcanic eruptions can increase the mortality risk. In 2023, the Popocatepetl volcano has registered recent intense activity, putting the area on high alert. Understanding local volcanic phenomena is essential to assist health personnel in providing informed and timely care. It is clear that health surveillance systems are required to monitor and help control the possible adverse health effects of volcanic eruptions. This review summarizes the most relevant evidence assessing the human health effects of emissions generated after volcanic eruptions and options for their control.

VolCID: A MATLAB-based GUI for the detection of volcanic vent clusters

In this work, a MATLAB Graphic User Interphase (GUI) is presented to support the identification of a clustered structure of eruptive centers for which only their spatial coordinates are known. The GUI, called VolCID (Volcano Cluster IDentification), combines an unsupervised classification scheme with user approval at various stages of the analysis. It is not necessary to make any assumption about the total number of clusters expected or about other characteristics of the clusters (as, for example, minimum cluster size) at the beginning of any analysis. Due to its flexibility, VolCID allows exploration of the effect of different distances of reference and to assess the possibility of chaining effects in a systematic and reproducible form. The combination of objective calculations and subjective choices therefore helps the operator to bring forward underlying assumptions (e.g., the expected number of clusters, general shape of each cluster, number of volcanoes per area of specific clusters) that often remain unstated in these types of studies. VolCID also incorporates the possibility of completing the analysis superimposed to an image of geologic significance, as well as to complete analysis of volcanic features on other planets. By facilitating the exploration of distribution schemes, VolCID might be a helpful tool that can be used to further our understanding of volcanic phenomena (or any other geologic feature that can be represented by point-like features) on Earth and other planets as well.

Changing magma recharge/discharge dynamics during the 2020–22 lava fountaining activity at Mt. Etna revealed by tilt deformation and volcanic tremor

Mt. Etna exhibited 62 lava fountaining events between December 13, 2020 and February 21, 2022. We analyzed tilt deformations and volcanic tremor amplitude time series, to characterize both eruptions and the preceding preparatory phases in terms of magnitude and speed of development of the volcanic phenomena, as well as to reconstruct the processes that took place inside the plumbing system and drove this intense period of activity. Based on deflation amplitudes associated with lava fountains and according with other retrieved parameters (i.e., magnitude of inflations, inflation and deflation velocities and volcanic tremor amplitudes), three periods have been distinguished. Period I displays higher values of all the aforementioned parameters, interpreted as conspicuous volumes of volatile-rich magma transferred towards the surface. Period II shows lower values evidencing lack of important new injections of magma from depth, whereas period III reveals a general increasing trend possibly related to gas flushing from magma residing in deeper portions of the plumbing system. Detailed elaborations of tilt signals allowed the identification of short-lived inflations accompanying the early stages of lava fountains during period II. Our results reveal significant correlations between amplitude and velocity of tilt and volcanic tremor signals associated with lava fountains and evidence the crucial role of gas in the inflation-deflation cycles.

Old and modern volcanic depictions as evidence of communities-volcanoes mutualism in Colombia

Studying the different ways in which the concept of volcanism is represented is crucial in the understanding of communities’ perception of the volcanic phenomena. In this contribution, 129 modern (2021-2023) depictions of volcanoes in Colombia between latitudes 0.82 and 5.96° N are described and classified into different contexts of use. Prehispanic depictions of volcanism are investigated in rock art sites (3 pictographs and 33 petroglyphs), and 15 distinct mythical narratives compiled and confirmed through interviews in the State of Nariño. We suggest that many of the rock art sites contain motifs that are reminiscent of the idea of volcanism, and that many of the folk tales include allusions to the volcanic concept. By collating the information contained in modern and older depictions, a link is established with the reality of the volcanic phenomena that shows how mutualism takes root between communities and volcanoes. The beneficial aspects derived from this relationship influence the perception of volcanic hazards in the region.

Geological significance of the spatial clustering and alignment of vents in zones of distributed volcanism: A critical review

The spatial distribution of volcanic activity has been the subject of scientific enquiry for more than 350 years. Nevertheless, it has been only until recently that modern techniques of analysis started to be used to characterize such distribution. As a result, in the past 40 years many methods were devised, or adopted from other fields of study, aiming to achieve that purpose. Ironically, the plethora of now available methodologies has made problematic the selection of one method of study to characterize the spatial distribution of volcanic vents. In addition, given the diversity of methods, and their underlying assumptions, there are issues concerning the form in which the results of any specific method should be interpreted in a volcanic context. In this work I make emphasis on the relationship between the embedded assumptions of several common methods of study with the concept of a “natural partition”. Throughout this work it is remarked that 1) it is extremely important to gain conscience about the several assumptions implicit on each method of analysis, 2) never loose sight that not all volcanic systems are equal, and 3) that it is a myth that any quantitative method can provide reliable information about any system. The convenience of assessing more than one conceptual model to explain the formation of a cluster-subcluster structure is also mentioned. Overall, it is shown that the complexity of volcanic phenomena cannot be encapsulated by using a single method of study, or an automatized selection of parameters. Thus, given the complexity and diversity of volcanic phenomena, there is no particular method, nor set of methods, that can be recommended to be used on every situation of interest. Yet, as a golden rule, it is suggested that more than one method of analysis is used at every location of study, looking for congruency of results within a range of spatial scales.

Array analysis of seismo-volcanic activity with distributed acoustic sensing

SUMMARY Continuous seismic monitoring of volcanoes is challenging due to harsh environments and associated hazards. However, the investigation of volcanic phenomena is essential for eruption forecasting. In seismo-volcanic applications, distributed acoustic sensing (DAS) offers new possibilities for long-duration surveys. We analyse DAS strain rate signals generated by volcanic explosions and tremor at Stromboli volcano (Italy) recorded along 1 km of dedicated fibre-optic cable. We validate DAS recordings with colocated nodal seismometers. Converting node measurements to strain rate, we observe a perfect match in phase between DAS and node waveforms. However, DAS amplitudes appear to be around 2.7 times smaller than those of node records, which we explain as due to the inefficient ground-to-fibre strain transfer in the loose cable. We invert time delays between strain rate waveforms and confirm that the DAS enables us to retrieve a dominant and persistent seismic source in the proximity of active craters. This stable source location is confirmed by node array analyses. Despite an observed high noise level of strain rate signals outside a range of 2–15 Hz, our results demonstrate the potential of this new technology in monitoring volcanic areas.

The April 2015 Calbuco eruption pyroclastic density currents: deposition, impacts on woody vegetation, and cooling on the northern flank of the cone

The 22-23 April 2015 eruption of the Calbuco volcano (Southern Andes, Chile) led to extensive pyroclastic density currents (PDCs) interactions with vegetation. We seek to describe the PDCs which affected both Tepu and Frío rivers, northern Calbuco, from their timing and deposition to cooling and erosion, as well as their impacts on forests. Our investigation is based on field stratigraphy, forest disturbance assessment, and geothermometry from degassing pipes and charcoal. These PDCs reached at least ~540-603 °C, as estimated from fumaroles, and consisted of both concentrated and dilute PDCs during the first pulse (22 April) at Tepu and mainly during the second pulse (23 April) at Frío. Effects of PDCs on forest vegetation recorded in Tepu consisted of heating, abrasion, burial, and impact force. On the valley floor, trees were buried with up to 4 m of deposits from the concentrated PDCs, and all trees in this deposition zone died with no subsequent sprouting. Conversely, in the margins of the valley, defoliated fallen trees and standing shrubs indicate scorching due to the passage of dilute PDCs, and some of them were later sprouting. Estimated impact forces required to produce toppling range from 1.5 to 3.7 kPa, and PDC velocities reached up to 36 m s-1. Charring of the buried wood involved an emplacement temperature of 400-550 °C within PDC deposits. The rapid watershed formation may have facilitated infiltration, decreasing the temperature in the basal part within the deposits at the Tepu river. Runoff during the subsequent months triggered lahars and caused the rivers to incise the deposits and transport sediment downstream. This set of observations provides valuable insights into how the interaction between volcanic phenomena and margine forest on the valley floors informs eruptive processes, dynamics, and impacts. Our study is also relevant to interpret the thermal history and potential hazards of PDCs.

Multiparametric Monitoring System of Mt. Melbourne Volcano (Victoria Land, Antarctica).

Volcano monitoring is the key approach in mitigating the risks associated with volcanic phenomena. Although Antarctic volcanoes are characterized by remoteness, the 2010 Eyjafjallajökull eruption and the 2022 Hunga eruption have reminded us that even the farthest and/or least-known volcanoes can pose significant hazards to large and distant communities. Hence, it is important to also develop monitoring systems in the Antarctic volcanoes, which involves installing and maintaining multiparametric instrument networks. These tasks are particularly challenging in polar regions as the instruments have to face the most extreme climate on the Earth, characterized by very low temperatures and strong winds. In this work, we describe the multiparametric monitoring system recently deployed on the Melbourne volcano (Victoria Land, Antarctica), consisting of seismic, geochemical and thermal sensors together with powering, transmission and acquisition systems. Particular strategies have been applied to make the monitoring stations efficient despite the extreme weather conditions. Fumarolic ice caves, located on the summit area of the Melbourne volcano, were chosen as installation sites as they are protected places where no storm can damage the instruments and temperatures are close to 0 °C all year round. In addition, the choice of instruments and their operating mode has also been driven by the necessity to reduce energy consumption. Indeed, one of the most complicated tasks in Antarctica is powering a remote instrument year-round. The technological solutions found to implement the monitoring system of the Melbourne volcano and described in this work can help create volcano monitoring infrastructures in other polar environments.

Fuzzy analytical network techniques for selecting suitable temporary refuge sites in Paez, Colombia

Colombia exhibits a considerable incidence rate of natural disasters because of its location within the intertropical zone, which exposes it to various meteorological and geological phenomena, including the Nevado del Huila volcano. The identification of suitable areas for the installation of temporary shelters is critical for managing these disasters. However, the task of identifying such locations is a complex problem that involves multiple criteria. This study uses a fuzzy systems approach to identify suitable sites for establishing temporary shelters in the Paez municipality during natural disasters, considering the essential criteria determined by experts through pairwise comparisons. The study results indicate that responsiveness is the most significant criterion, followed by area profile. Using these criteria, it identified a specific locality in the Paez municipality as suitable for establishing temporary shelters during natural disasters caused by volcanic phenomena. The findings were compared with those obtained from existing scientific literature and validated by experts in natural disasters. The methodological process described in this study provides a valuable tool for public entities to make informed decisions concerning natural disasters in indigenous territories caused by volcanic phenomena.

A review of the tectonic, volcanological and hazard history of Vulcano (Aeolian Islands, Italy)

AbstractVulcano is one of the seven volcanic islands composing the Aeolian Islands archipelago (Southern Italy), which also includes three other active volcanoes. The island was originally a stratovolcano like Stromboli; afterwards, its shape turned towards a complex structure composed of several volcanic landforms of different sizes. This is due to the great variability of the tectonic and volcanic phenomena, presently showing a volcano made by two calderas, a lava dome complex and two small active cones. The largest of them is the tuff cone of La Fossa, hosted in the middle of a 3‐km‐wide caldera structure (La Fossa caldera), whose borders are visible on the southern and western sides of the island. Its last eruption occurred in 1888–1890. At present, Vulcano is characterized by weak shallow seismicity and intense fumarolic activity mainly concentrated within the crater of the La Fossa cone and along its rims during a recent unrest phase started in 2021, and measured with a multiparametric monitoring network.

A summary of peer-reviewed resources for teaching volcanology in higher education

Here, we summarise and categorise the volcanology learning activities identified and described in a systematic literature review of volcanology higher education (a companion article; Dohaney et al. [2023]). We share the 47 peer-reviewed articles organised by useful categories, such as educational level, mode and setting of learning, volcanic phenomena, and skills learned in the curricula for easier use and navigation by volcanology instructors. Based on the claims made in the peer-reviewed resources, considerations and suggestions for improved volcanology teaching are included, e.g. exploring authentic field-based experiences, local sites, or simulated demonstrations of volcanic phenomena. To support use of these curricula, we provide suggestions for adapting the resources and highlight additional online catalogues that house useful and engaging volcanology teaching materials.

Assessing long-term tephra fallout hazard in southern Italy from Neapolitan volcanoes

Abstract. Nowadays, modeling of tephra fallout hazard is coupled with probabilistic analysis that takes into account the natural variability of the volcanic phenomena in terms of eruption probability, eruption sizes, vent position, and meteorological conditions. In this framework, we present a prototypal methodology to carry out the long-term tephra fallout hazard assessment in southern Italy from the active Neapolitan volcanoes: Somma–Vesuvius, Campi Flegrei, and Ischia. The FALL3D model (v.8.0) has been used to run thousands of numerical simulations (1500 per eruption size class), considering the ECMWF ERA5 meteorological dataset over the last 30 years. The output in terms of tephra ground load has been processed within a new workflow for large-scale, high-resolution volcanic hazard assessment, relying on a Bayesian procedure, in order to provide the mean annual frequency with which the tephra load at the ground exceeds given critical thresholds at a target site within a 50-year exposure time. Our results are expressed in terms of absolute mean hazard maps considering different levels of aggregation, from the impact of each volcanic source and eruption size class to the quantification of the total hazard. This work provides, for the first time, a multi-volcano probabilistic hazard assessment posed by tephra fallout, comparable with those used for seismic phenomena and other natural disasters. This methodology can be applied to any other volcanic areas or over different exposure times, allowing researchers to account for the eruptive history of the target volcanoes that, when available, could include the occurrence of less frequent large eruptions, representing critical elements for risk evaluations.

Impact assessment caused by bradyseism phenomena in the Campi Flegrei area

Campi Flegrei (Italy) is among the areas with the greatest volcanic explosive risk in the world due to the dangerousness of the expected hazards, the high exposed value (about 500,000 people will be evacuated during the “alarm phase”), and the vulnerability of the urban settlements under the effect of the volcanic phenomena. The last two dramatic bradyseism phases occurred in 1969–1972 and 1982–1984 when Pozzuoli town was affected by rapid ground inflation, which brought an overall higher level of about 3.5 m and caused numerous earthquakes (M ≤ 4.2), with severe damage to buildings. During 1984, the seismicity was intense, with 33 events with 0.5 < M ≤ 3 and six with 3 < M ≤ 3.8. Subsequently, the Campi Flegrei caldera was characterized by general subsidence for about 20 years until 2005, when a new inflation period started and is still ongoing (∼1 m). The areal distribution of the recent uplift is characterized by the maximum vertical displacement in the town of Pozzuoli, with a radial decrease from the caldera center outwards. The need to better understand Campi Flegrei volcanic activity is fundamental to protecting the population from hazards linked to explosive volcanic eruptions and understanding the role of seismicity as a possible precursor of a potential eruption. In this perspective, as part of the activities of the PLINIVS Study Centre (Centre of Competence of Italian Civil Protection Department for Volcanic Risk), the authors developed a procedure, implemented in a web application, that relates the monitoring of the ground deformation with the behavior of buildings to evaluate the level of progressive damage to the ordinary Phlegraean buildings due to bradyseism in near real time. This study describes the models adopted for the three impact/risk factors (hazard, exposure, and vulnerability) used to estimate building damage.

Experimental Measurement of Enhanced and Hindered Particle Settling in Turbulent Gas‐Particle Suspensions, and Geophysical Implications

AbstractThe dynamics of geophysical dilute turbulent gas‐particles mixtures depends to a large extent on particle concentration, which in turn depends predominantly on the particle settling velocity. We experimentally investigate air‐particle mixtures contained in a vertical pipe in which the velocity of an ascending air flux matches the settling velocity of glass particles. To obtain local particle concentrations in these mixtures, we use acoustic probing and air pressure measurements and show that these independent techniques yield similar results for a range of particle sizes and particle concentrations. Moreover, we find that in suspensions of small particles (78 μm) the settling velocity increases with the local particle concentration due to the formation of particle clusters. These clusters settle with a velocity that is four times faster than the terminal settling velocity of single particles, and they double settling speeds of the suspensions. In contrast, in suspensions of larger particles (467 μm) the settling velocity decreases with increasing particle concentration. Although particle clusters are still present in this case, the settling velocity is decreased by 30%, which is captured by a hindered settling model. These results suggest an interplay between hindered settling and cluster‐induced enhanced settling, which in our experiments occur respectively at Stokes number O(100) and O(1). We discuss implications for volcanic plumes and pyroclastic currents. Our study suggests that clustering and related enhanced or hindered particle settling velocities should be considered in models of volcanic phenomena and that drag law corrections are needed for reliable predictions and hazard assessment.

Evolving shallow conduit revealed by tremor and vent activity observations during episodic lava fountaining of the 2021 Geldingadalir eruption, Iceland

Cyclic behaviour is observed in volcanic phenomena ranging from caldera collapses to explosions, spattering or lava fountaining. The repeating processes can define irregular, regular or systematically changing patterns. These patterns yield information about the subsurface structure, which often is not considered in detail. We analyse the pattern of 7058 lava fountaining episodes that occur between 2 May and 14 June 2021 during the Geldingadalir eruption, Iceland. Our seismometer records the lava fountaining episodes as tremor episodes. We analyse the seismic tremor amplitude, the episode duration, the repose time and the sum of episode duration and repose time (cycle duration). We define six periods characterised by different patterns: Three periods feature long episodes that exponentially shorten with time. One period features coexisting long and short episodes in a haphazard sequence. One period shows a stable pulsing duration but increasing repose time, and one period has stable, short episodes and repose times. We conclude that the episodic fountaining starts because a shallow-conduit container forms on 2 May shifting the magma degassing from sustained continuous to an episodic state. This situation evolves until 11 May when a semi-stable state is reached. The length of the repose times is most likely influenced by the amount of outgassed magma present in the uppermost part of the shallow conduit. Finally, we suggest that the vent is mechanically eroded and widens with time causing increasing seismic tremor amplitudes. However, the trends are frequently punctuated by partial crater wall collapses that temporarily disrupt the system.

Automatic Detection of the Explosive Activity of the Mt. Etna Volcano through Doppler Radar Monitoring

Improving the capability to detect volcanic explosive activity could be strategic for the task of a volcano observatory to inform civil protection authorities and air traffic controllers. The detection of explosive volcanic activity can be done in real time and also under bad visibility conditions by using the radar remote sensing technique. Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (INGV-OE) installed an S-band pulse Doppler radar in a shelter located at about 3 km south of the active volcanic vents in order to enhance the Etna volcano’s surveillance. Here, we describe the realisation of a system that exploits such device, aimed at continuously monitoring the explosive eruptive activity at the Mt. Etna summit craters through an automatic processing flow of the radar data. We analysed the signals recorded during 23 eruptive episodes that occurred at the Etna South-East Crater during the second half of 2021; these episodes were characterised by an opening Strombolian activity and the subsequent evolution into a lava fountain. To identify the onset of both volcanic phenomena, empirical thresholds of radar time series were extracted with the help of thermal and visible images acquired by the INGV-OE cameras’ network. The resulting monitoring tool automatically operates 24/7 for volcanic surveillance, providing real-time data to the INGV-OE control room.

Semantic segmentation of explosive volcanic plumes through deep learning

Tracking explosive volcanic phenomena can provide important information for hazard monitoring and volcano research. Perhaps the simplest forms of monitoring instruments are visible-wavelength cameras, which are routinely deployed on volcanoes around the globe. Here, we present the development of deep learning models, based on convolutional neural networks (CNNs), to perform semantic segmentation of explosive volcanic plumes on visible imagery, therefore classifying each pixel of an image as either explosive plume or not explosive plume. We have developed 3 models, each with average validation accuracies of >97% under 10-fold cross-validation; although we do highlight that, due to the limited training and validation dataset, this value is likely an overestimate of real-world performance. We then present model deployment for automated retrieval of plume height, rise speed and propagation direction, all parameters which can have great utility particularly in ash dispersion modelling and associated aviation hazard identification. The 3 trained models are freely available for download at https://doi.org/10.15131/shef.data.17061509.