No abstract

We used a large set of satellite- (visible, infrared, and radar images from Planetscope, MODIS, VIIRS, Sentinel2, Landsat 8, and Sentinel 1) and ground-based data (optical images, SO2 flux, shallow seismicity) to describe and characterize the activity of the Sabancaya volcano during the unrest and eruption phases that occurred between 2012 and 2020. The unrest phase (2012–2016) was characterized by increasing gas and thermal flux, sourced by a convective magma column rising along with the remnants of a buried plug still permeable to fluid flow. Conversely, a new conduit, adjacent to the previous one, fed the eruptive phase (2016–2020) which was instead characterized by a discontinuous extrusive activity, with phases of dome growth (at rates from 0.04 to 0.75 m3 s−1) and collapse. The extrusive activity was accompanied by fluctuating thermal anomalies (0.5–25 MW), by irregular SO2 degassing (700–7000 tons day−1), and by variable explosive activity (4–100 events d−1) producing repeated vulcanian ash plumes (500–5000 m above the crater). Magma budget calculation during the eruptive phase indicates a large excess of degassing, with the volume of degassed magma (0.25–1.28 km3) much higher than the volume of erupted magma (< 0.01 km3). Similarly, the thermal energy radiated by the eruption was much higher than that sourced by the dome itself, an unbalance that, by analogy with the degassing, we define as “excess thermal radiation”. Both of these unbalances are consistent with the presence of shallow magma convection that fed the extrusive and explosive activity of the Sabancaya dome.

During explosive volcanic eruptions, large quantities of tephra can be dispersed and deposited over wide areas. Following deposition, subsequent aeolian remobilisation of ash can potentially exacerbate primary impacts on timescales of months to millennia. Recent ash remobilisation events (e.g., following eruptions of Cordón Caulle 2011; Chile, and Eyjafjallajökull 2010, Iceland) have highlighted this to be a recurring phenomenon with consequences for human health, economic sectors, and critical infrastructure. Consequently, scientists from observatories and Volcanic Ash Advisory Centers (VAACs), as well as researchers from fields including volcanology, aeolian processes and soil sciences, convened at the San Carlos de Bariloche headquarters of the Argentinian National Institute of Agricultural Technology to discuss the “state of the art” for field studies of remobilised deposits as well as monitoring, modeling and understanding ash remobilisation. In this article, we identify practices for field characterisation of deposits and active processes, including mapping, particle characterisation and sediment traps. Furthermore, since forecast models currently rely on poorly-constrained dust emission schemes, we call for laboratory and field measurements to better parameterise the flux of volcanic ash as a function of friction velocity. While source area location and extent are currently the primary inputs for dispersion models, once emission schemes become more sophisticated and better constrained, other parameters will also become important (e.g., source material volume and properties, effective precipitation, type and distribution of vegetation cover, friction velocity). Thus, aeolian ash remobilisation hazard and associated impact assessment require systematic monitoring, including the development of a regularly-updated spatial database of resuspension source areas.

&lt;p&gt;&lt;span&gt;&lt;span&gt;Arequipa, the second most populated city located in the South of Peru, is full of history, culture and is a UNESCO World Heritage site. Its natural attractions and geological diversity stand out, like the Colca and Andagua UNESCO Global Geopark, as well as geosites within the city. This provides a basis for improving the population's environmental awareness and resilience, a process that partly starts with geosite inventorying, used in socio-economic exchange with the population. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;For the geosite work several methods were used from the early Cendrero (1996) to most recent Brilha (2016). As a first stage, potential geosites were field identified, and we established their representativeness, integrity, rarity, scientific knowledge level and geological value. Six major potential geosites were identified: 1) Sillar quarries, 2) Rio Chili valley, 3) Misti and Chachani volcanoes viewpoint, 4) Nicholson volcano, 5) Ccapua monogenetic volcanoes, Yura Viejo, Uyupampa and 6) Domo el Volcancillo. Once identified and judged suitable for potential use and protection, the six sites were qualitatively evaluated for intrinsic value, potential for use and need for protection, thus completing more detailed information on each one. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;In this second stage, the process of quantifying the value and relevance establishing a ranking. The Brilha (2005) methodology was used to classify geosites as local - regional and national - international interest, The Sillar being of national - international scope, while the other geosites are of local to regional scope. To rank geosites according to their scientific value, educational potential use, tourism potential use and the risk of degradation, the Brilha (2016) methodology was used. Each site was evaluated independently, since the value of the geosite is not directly related to its potential for use or vulnerability. The ranking for scientific value and educational and tourist use is different and the Sillar and Ccapua have high risk of degradation, while the others moderate risk. We also classified each site for its natural risk to inhabitants, users and visitors, making a preliminary safety plan for each site. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;The process ends with a classification seeking to provide a legal basis for geoheritage management and protection. Conservation plans take into account the degradation risk to propose strategies with include safety. Community involvement was a first step, with the Sillar site users partly initiating and directing our work. We all see the geoheritage as a tool to publicize both geology and associated activities in an innovative way through geotourism and economic sustainability. Risk is managed with geosites and the benefits and dangers related to the Misti and Chachani volcanoes communicated. The process continues with constant monitoring of geosites. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;This aims to empower local scientists and residents, because it highlights the geological heritage, and generates &quot;tools&quot; for education and promote resilient communities in the face of geological hazards; in addition, diversify the alternatives for geotourism. It is part of the UNESCO IGCP Geoheritage for Resilience, project 692.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;

Arequipa (Peru) is an area where volcanic activity has been persistent during the Quaternary. Studies carried out in this area have highlighted the emplacement of ignimbrite deposits, large volcanic clusters and stratovolcanoes. Monogenetic volcanism is also present, although poorly explored and studied. Due to its location over an ignimbrite plain and poor state of preservation, the only identified monogenetic cone in the Arequipa basin was the Nicholson volcano, while other monogenetic centers remained unknown. This lack of information about the recent volcanism can lead to inadequate definition of scenarios in a hazard assessment in the region. The present study has investigated monogenetic volcanism in the northwestern edge of the Arequipa basin based on geological survey, geochronology and geochemical data. Here, we report for the first time five small volcanic centers such as Yura Viejo, Ccapua, Uyupampa, El Chiral and Patacocha, which together with the Nicholson volcano form the Yura Monogenetic Field. Stratigraphic considerations and new 40Ar/39Ar ages allow us to place the eruptive activity in the Middle–Upper Pleistocene (c. 195–54 ka). Phreatomagmatic, Strombolian and effusive eruptions characterize the monogenetic activity of the field. As a result of these eruptions, small scoria cones, maars, and lava flows/coulées were generated. The eruptive products show ubiquitous olivine phenocryst-rich (&lt;10 vol%) set in a fine pilotaxitic groundmass, suggesting rapid ascent of basaltic magmas to the surface controlled by the tectonic setting. The analyzed rocks lie in a narrow range of basaltic-andesite composition (50.9–55.6 wt% SiO2) being the most mafic Pleistocene - Recent volcanic products identified in the Arequipa basin, along with the least differentiated magmas from the nearby Chachani volcanic cluster. This work shows how monogenetic volcanism can occur contemporaneous and closely spaced to larger volcanic clusters and active stratovolcanoes. We hope the information provided here will contribute to improve the risk management by highlighting the scenario of monogenetic eruptions that should be considered in the hazard assessment.