Editorial on the Research Topic: Review in Volcanology 2023

Nick Varley^1*Marisa Giuffrida^2*

• ¹University of Colima, Colima, Mexico
• ²Universita degli Studi di Catania, Catania, Italy

Over the last few decades, Volcanology has rapidly evolved from a natural science, based on primarily eyewitness observations and description of natural phenomena, to a quantitative multidisciplinary science (Heiken, 2013;Acocella, 2014). Field observations are now complemented by increasingly precise measurements, both in situ and remote, laboratory experiments and sophisticated physical and numerical models, aimed at reproducing a variety of processes considering both crustal and subaerial systems (Cashman and Sparks, 2013). Satellite-based imaging in particular has revolutionised the science, with the possibility of rapid information retrieval for any point on the Earth's surface (Thompson et al. 2023). This progress has greatly improved our understanding of volcanic phenomena, ultimately helping to reduce the large uncertainties that characterize volcanic eruption forecasts. Fink et al. (2023) highlight three factors that generate advances in science: improvements in technology, conceptual breakthroughs and the changing needs of society, adding for volcanology, the effect of specific "signature" eruptions that have precipitated a significant focus on critical aspects. This is clear with eruptions such as Mt. St. Helens, USA in 1980, Pinatubo, Philippines in 1991, Soufrière Hills, Montserrat in 1995-2010, and most recently the Hunga Tonga-Hunga Ha'apai, Tonga 2022 eruption, each generating an extraordinary amount of interest for specific reasons in each case.In this Research Topic, we gathered review articles that integrate and advance existing knowledge and highlight new perspectives in the study of volcanoes. The collection of articles presented here covers a range of key topics in the field of Volcanology, spanning from the analysis of tools and systems applied to volcanic monitoring to the implementation of modelling strategies for hazard and risk assessment in active volcanic areas. Each contribution to this Research Topic demonstrates the importance of examining past issues to address the current challenges and draw future potential directions for volcanological investigations. A brief summary of each article is given below.Hayes et al. focus on how to best deal with volcanic risk assessments through the use of reliable vulnerability models. In their contribution, the authors review the current state of volcanic vulnerability model development, discuss the challenges surrounding data collection, modelling strategies and uncertainty characterization, and highlight future directions to improve the model accuracy for use in different contexts. From the number and diversity of models available globally, it is clear that major progress has been made in the volcano vulnerability model development over the last few decades, due both to an improved collection of empirical high-quality data and the intensification of interdisciplinary collaborations. What emerges in the perspective of robust volcanic impact and risk assessment, is the need for enhanced testing/validation procedures, and treatment of the uncertainty to improve the model accuracy, in order to ensure that reliable risk information is provided to decision-makers.The complex, unpredictable behaviour of many volcanic phenomena makes eruption forecasting and risk mitigation particularly challenging (Tillings, 1989). Jones et al. address the issue, highlighting the many difficulties faced in developing risk management strategies in the presence of pyroclastic density current (PDC) hazards. The study emphasizes how precise measurements and characterization of both the physical properties of PDC deposits as well as the individual solid particles are critical to infer transport dynamics, emplacement mechanisms and the impact of PDCs. Currently, PDC behaviour is investigated by field reconstructions, detailed experimental studies and numerical models simulating flow dynamics and propagation, which require the input of predetermined physical property data. The incorporation of key physical property data in analogue and numerical models is, therefore, described and discussed in light of the scientific progress that has been made in PDC modelling over time. An emphasis is given to topics that are emerging thanks to the development of new methods and advances in computation capabilities. Emerging studies, including measurements of the particle electrical charge, granular flow rheology, characterization of ultra-fine ash and thermal properties of PDCs, are opening new opportunities for assessing the impact of these complex phenomena.The study of Williams & Ramsey looks into the analytical potential of infrared reflectance and emission spectroscopy and related applications in volcanology. The applications vary from the analysis of rock samples in a laboratory setting to ground-based, airborne, and satellite imaging of large areas. The article discusses the basic principles of spectroscopy and details the methods for acquiring high-fidelity laboratory measurements, considering both low-and high-temperature emission and reflectance spectroscopy. It then moves to ground-based, airborne, and satellite data collection, highlighting the types of instruments and their applications in volcano monitoring, hazard assessment, and planetary science. The focus is, therefore, on the current state of spectroscopic studies in volcano science and where measurements may improve for the type of analysis desired. A discussion about how laboratory measurements compare to those taken from remote sensing instrumentation is also provided.Satellite technology now offers the ability to detect and monitor volcanic activity in even the most remote corners of the globe, where ground instruments are absent or may be inaccessible (Poland et al., 2020). In this context, Coppola et al. synthetize and discuss the advances in satellite thermal monitoring of active volcanoes following the development of automated hotspot detection systems, such as MODVOLC (Wright et al., 2002;Wright et al., 2004) and MIROVA (Coppola et al., 2020), capable of quantifying the energy radiated by volcanic features. In their contribution, the authors present the first MIROVA database, a database of infrared satellite data which includes 20 years of thermal observations at the most active volcanoes in the world. From the analysis of thermal emissions at the targeted volcanoes, some relationships emerge between the radiated energies and erupted lava volumes for compositional-distinct groups volcanoes. By allowing a direct comparison between the current thermal emission of a volcano with its long-term ordinary emission, this multiyear database also provides a valuable record for assessing volcanic hazards.Scoria cones represent the most common type of volcano on our planet. There are various reasons to study their dimensions, for example, to determine their age, appreciate their potential hazards, or understand the evolution of the local magmatic system. Bailey et al. review the different techniques that have been applied to this end, dividing them into two broad types: earlier methods were based on physical measurements with volumes derived from their geometry, later studies have utilized digital elevation models to more precisely match the actual terrain. Surprisingly large errors are possible, which are frequently not considered. The paper emphasizes the advantages and limitations of the different approaches, with the aim of assisting the selection of appropriate methodology, making it a useful resource for future research.In conclusion, the articles in this Research Topic highlight the diversity of volcanological studies and their evolution in the frame of the technological improvements of the last decades. Although the level of knowledge to date may still not completely answer the many questions about the nature and evolution of volcanic systems, it does provide a solid basis for planning more in-depth investigations.