In recent decades, the city of Arequipa, Peru, has experienced rapid and largely unplanned urban growth, increasing its exposure to lahars (debris and hyperconcentrated flows) triggered by intense rainfall during the rainy season (December - March). These flows descend through ravine channels from the Misti volcano, causing significant damage and loss of life in suburban areas and the historic center of Arequipa. This context underscores the urgent need for an efficient, real-time, and continuous lahar monitoring system. Here we present the development and implementation of an Automatic Lahars Monitoring System (ALMS) deployed across six ravines that extend from the SW flank of Misti volcano and cross the city of Arequipa. The ALMS is an improved version of the Huaicos Monitoring System (SMH), which has operated since 1990 in the Quebrada Rioseco near Lima, Perú. The ALMS comprises ten autonomous, solar-powered remote stations equipped with radar motion sensors, LiDAR level sensors, surveillance cameras, and machine-learning-based image analysis for continuous monitoring and detection of lahar activity. During the 2024–2025 rainy season, the ALMS successfully detected two lahar events in the Quebrada El Pato and Quebrada Venezuela channels, demonstrating its operational reliability and effectiveness as an early-warning tool. Owing to its low cost, modular design, and robust performance, the ALMS represents a scalable solution that can be replicated in other volcanic and non-volcanic regions to reduce the impacts of debris flows and enhance disaster risk management.

Sabancaya volcano is one of the most active volcanoes in the Central Andes. Its ongoing eruptive process is accompanied by large-scale deformation, with activation of the Huambo-Cabanaconde fault system, marked by intense seismicity over an area of about 50 & times; 30km(2) . We present a pilot magnetotelluric survey performed in 2022, covering the Ampato-Sabancaya complex, Hualca-Hualca volcano, as well as the related system of normal faults. Our three-dimensional electrical resistivity model reveals pronounced vertical gradients and lateral contrasts at elevations above sea level, along with generally low resistivity values at depth. Seismicity at depths >4 km below sea level predominantly occurs in a low resistivity environment: 90% of seismic events occur at resistivity values below 10 Omega m. Two prominent electrical conductors (<0.5 and 2-4 Omega m) are imaged at depths 11-18 km and 3-8 km, respectively. Using petrological constraints, we interpret them as the signature of the magmatic plumbing system, connecting the Hualca-Hualca and Ampato-Sabancaya volcanoes. The deeper conductor is inferred to represent a magma reservoir situated beneath the older Hualca-Hualca volcano, consistent with long-term deformation and seismicity. It is connected to the laterally offset shallow magma chamber below Sabancaya. At depth 2-10 km, a strong conductor (<0.1 Omega m) is imaged in the Huambo-Cabanaconde fault zone. The extremely high conductivity of this body is attributed to the abundance of ultra-saline brines, originating from the deep magma reservoir below. We speculate that the strong seismicity cluster detected in 2013 facilitated the passage of magmatic fluids exsolved from the magma reservoir, and replenished this ultra-conductive body.

Volcan Misti, situated in the Central Volcanic Zone (CVZ) is considered one of the most hazardous volcanoes in South America. Petrophysical and mineralogical studies of the erupted materials inferred the presence of an interactive and stratified magmatic system, composed of two to three magma reservoirs. However, its geometry and the relationships with tectonic and seismic activity remain largely unresolved due to the lack of high-resolution geophysical imaging. To address this question, 42 broadband magnetotelluric (MT) stations were deployed around the volcanic edifice to construct the first three-dimensional electrical resistivity model of the magmatic and hydrothermal system. The data were inverted and the resulting model was characterized by three low-resistivity features. The first is a conductive layer, similar to 1 km thick (5 to 40 Omega m), that extends laterally beneath the volcanic edifice and is interpreted as a clay cap. The second feature corresponds to an inferred low-resistivity body (10-30 Omega m), located at sea level. The third is a low-resistivity body (< 10 Omega m) imaged at similar to 10 km below sea level, located slightly east of the volcano (similar to 2.5 km). The resistivity of this feature is interpreted as indicative of the presence of andesitic melts, suggesting a melt fraction in the range 4-24% for the temperature range 900-950 degrees C. The seismicity associated with the volcano is minimal and concentrated just beneath the crater at a depth of similar to 2.5 km. The shallow depth of the seismicity, together with the MT model, suggests that the recharge and supply of magma occur in a cryptic manner.

Most of the nitrogen (N) accessible for life is trapped in dinitrogen (N2), the most stable atmospheric molecule. In order to be metabolized by living organisms, N2 has to be converted into biologically assimilable forms, so-called fixed N. Nowadays, nearly all the N-fixation is achieved through biological and anthropogenic processes. However, in early prebiotic environments of the Earth, N-fixation must have occurred via natural abiotic processes. One of the most invoked processes is electrical discharges, including from thunderstorms and lightning associated with volcanic eruptions. Despite the frequent occurrence of volcanic lightning during explosive eruptions and convincing laboratory experimentation, no evidence of substantial N-fixation has been found in any geological archive. Here, we report on the discovery of a significant amount of nitrate in volcanic deposits from Neogene caldera-forming eruptions, which are well correlated with the concentrations of species directly emitted by volcanoes (sulfur, chlorine). The multi-isotopic composition (δ18O, Δ17O) of the nitrates reveals that they originate from the atmospheric oxidation of nitrogen oxides formed by volcanic lightning. According to these first geological volcanic nitrate archive, we estimate that, on average, about 60 Tg of N can be fixed during a large explosive event. Our findings hint at a unique role potentially played by subaerial explosive eruptions in supplying essential ingredients for the emergence of life on Earth.

We investigate ten of the most recent tephra-fall deposits emplaced between <= 21 and 2 ka from the Pacheco stage of Misti volcano, Peru, to elucidate magma dynamics and explosive eruption triggers related to magma storage, recharge, and remobilization. Whole-rock, glass, and mineral textures and compositions indicate the presence of broadly felsic, intermediate, and mafic magmas in a chemically and thermally stratified magma storage system (Zones 1-3) that interact to differing extents prior to eruption. Intermediate magmas are defined by plagioclase + amphibole + two-pyroxenes + Fe-Ti oxides and phase equilibria indicate they formed at similar to 300 to 600 MPa and similar to 950 degrees C to 1000 degrees C. Intermediate magmas dominate the Pacheco stage and either erupted alone as hybridized magmas or mingled with minor volumes of cool felsic magmas (similar to 800 degrees C) in which only plagioclase + Fe-Ti oxides are stable. Felsic magmas do not exclusively comprise any tephra-fall deposit emplaced during the Pacheco stage but were remobilized by recharge and mixing with intermediate magmas in order to erupt. Furthermore, felsic-hosted amphibole cognate to the intermediate magmas are reacted despite the felsic magmas being water saturated, which suggests they are staged above the amphibole stability limit (<= 200 MPa). The cryptic presence of mafic magmas is indicated by high-An plagioclase cores (An(74-88)), rare anhedral olivine (Fo(77-80)), and possibly high Mg# augite and amphibole (up to Mg# 84 and 77, respectively). The dearth of basalt to basaltic andesite melts recorded in erupted glasses and exclusivity of high-An plagioclase to crystal cores signals mafic magmas are staged deeper in the crust than the intermediate magmas. Periodic interactions between these magmas tracked via glass compositions and crystal exchange reveal an alternation between the production of mingled magmas and their eruption shortly after a recharge event, followed by a period of homogenization and eruption of hybridized magmas. As such, we identify magma recharge as a key mechanism by which half of the explosive eruptions were triggered in the Pacheco stage. A >100 degrees C increase in Misti's fumarole temperatures from 1967 to 2018 coincident with changes in fumarolic gas compositions is consistent with degassing of a mafic recharge magma, signaling that Misti could produce similar explosive eruptions in the future.

On Earth, most of the nitrogen (N) accessible for life is trapped in dinitrogen (N2), which is the most stable atmospheric molecule. In order to be metabolised by living organisms, N2 has to be converted into assimilable forms, also called fixed N. Nowadays, nearly all the N-fixation is achieved through biological and anthropogenic processes. However, in early environments of the Earth, before the emergence of life, N-fixation must have occurred via natural abiotic processes. Electrical discharges, including from thunderstorms and also lightning associated with volcanic eruptions is one of the most invoked processes. The occurence of volcanic lightning during explosive eruptions is frequent, and convincing laboratory experimentations support the role of this phenomenon, however no evidence of substantial N-fixation has been found in volcanic records. Here we report on the discovery of large amounts of nitrates in volcanic deposits from Neogene caldera-forming eruptions, which are well correlated with the concentrations of species directly emitted by volcanoes such as sulphur and chlorine. The multi-isotopic composition (δ18O, Δ17O) of the nitrates reveals that they originate from the atmospheric oxidation of nitrogen oxides formed by volcanic lightning that occur during the eruption. According to these volcanic nitrate records, our first estimates suggest that about 60 Tg of N can be fixed during a large explosive event. Our findings hint at a unique role potentially played by subaerial explosive eruptions in supplying essential ingredients for the emergence of life on Earth.

Between 38.5 ka cal BP and 32.4 ka cal BP, a dacitic Volcanic Explosivity Index 5 eruption at Misti volcano emplaced the Sacarosa tephra-fall deposit. Its biotite phenocrysts, fine grain size, scarce lithics, and abundant loose crystals characterize the deposit at locations sampled. The eruption’s ~ 800 °C magma rose rapidly from ~ 10 km depth, culminating in a Plinian eruption which reached a mass eruption rate of 7.7 × 10 6 –4.1 × 10 7 kg/s and emplaced about 3 km 3 of tephra within tens of hours. The unit comprises two layers of subequal thickness separated by a diffuse contact with the upper distinguished by being slightly coarser and less well sorted than the lower. The deposit’s coarser upper layer indicates either climactic conditions or a lesser degree of fragmentation during the latter half of the eruption. Strong winds distributed the deposit southwest of Misti, where it crops out over at least 800 km 2 and drapes the present site of Arequipa with up to 100 cm of tephra. The Sacarosa deposit is the first among the Cayma stage deposits, a distinctive group of felsic, biotite-bearing units, to be carefully described and its eruption characterized. Several Cayma stage deposits were emplaced by voluminous explosive eruptions similar to the Sacarosa eruption, representing a ~ 8.9–15.5 ky interval of powerful eruptions. Such an explosive eruption today would threaten Arequipa’s over 1,100,000 residents, many of whom live within the Sacarosa deposit’s distribution.

In order to gain insights into continental arc magmatic processes, we have conducted a petrological and geochemical study of major and trace elements and Sr, Nd, and Pb isotopes of the Ampato-Sabancaya compound volcano, which belongs to the Andean Central Volcanic Zone (CVZ). Whole-rock compositions for Ampato and Sabancaya range from andesites to dacites (56.7-69.3 wt% SiO2) and both belong to a medium- to high-K calkalkaline magmatic series. Ampato-Sabancaya samples are characterized by high contents of large-ion lithophile elements (LILE; e.g., K, Rb, Ba, Th), low concentrations of high field strength elements (HFSE; e.g., Nb, Zr) and heavy rare earth elements (HREE; e.g., Yb), with consequently high La/Yb and Sr/Y ratios. An increase in these ratios is usually interpreted as a result of magmatic differentiation in the presence of garnet in the deep crust. A detailed analysis reveals that the rocks of Ampato-Sabancaya display three different compositional groups. (1) The first, composed mainly of andesites (56.7-59.8 wt% SiO2), corresponds to lavas from the early stage of the Ampato Basal edifice, as well as pyroclastic deposits from the Ampato Upper edifice. (2) The second group corresponds to andesitic and dacitic compositions (60.0-67.3 wt% SiO2) from the Ampato Basal edifice (Moldepampa stage), the Ampato Upper edifice, and the Sabancaya edifice. (3) The third group corresponds to dacitic compositions (65.0-69.3 wt% SiO2) associated with the Corinta Plinian fallout and pyroclastic flow deposits from the Ampato Upper edifice. This last group of dacites, erupted during the Ampato Upper edifice stage, have drastically different compositions from the other groups with Sr/Y (<27) and Sm/Yb (<4.7) ratios lower than other lavas and lacking evidence of amphibole and/or garnet fractionation during their genesis. As a whole, Sr, Nd, Pd isotopic ratios suggest that mantle-derived magmas are significantly affected by assimilation processes during their evolution, due to the thick (65-70 km) continental crust beneath the CVZ in southern Peru. In summary, the magmatic evolution of group 1 and 2 can be explained by a two-step model in which primitive magmas evolved in the deep crust in the so-called melting-assimilation-storage-homogenization (MASH)-type reservoirs by assimilation-fractional crystallization (AFC) processes involving garnet and/or amphibole. Then, amphibole-dominated upper crustal AFC processes and magma mixing are responsible for the geochemical diversity of the main ASCV trend. In contrats, the group 3 dacites followed an upper crustal AFC process (without amphibole) from a different primitive magma, which did not suffer the high pressure, garnet-dominated AFC processes. This evolution highlights the complexities associated to magma genesis and differentiation at continental arcs contructed on a thick crust.

Sabancaya volcano is the youngest and second most active volcano in Peru. It is part of the Ampato-Sabancaya volcanic complex which sits to the south of the ancient Hualca Hualca volcano and several frequently active faults, thus resulting in complex volcano-tectonic interactions. After 15 years of repose, in 2013, a series of 4 earthquakes with magnitude >4.5 occurred within 24 h, marking the beginning of a new episode of unrest. Several additional swarms of earthquakes occurred in the following years until magmatic eruptive activity started on 6 November 2016. This activity is ongoing as of this writing, with an average of 50 explosions per day. In this study, we present results of multiparametric monitoring of Sabancaya's activity observed during 2013-2020. Seismic data are used to create a one-dimensional seismic velocity model, to catalog, locate, and characterize earthquakes, to detect repeating earthquake families, and to monitor seismic velocity variations by ambient noise cross-correlation. These analyses are complemented by visual and remote sensing observations and ground deformation measurements. All monitored parameters showed significant changes on 6 November 2016, the day of eruption onset, thus dividing the eruptive activity into pre-eruptive and eruptive stages.The unrest is characterized by high levels of seismic activity with hundreds of events detected per day. Volcano-tectonic (VT) earthquakes were dominant during the pre-eruptive period while long-period (LP) events and explosions have been most numerous since the eruption onset. Earthquake locations highlight long-lasting seismogenic zones along multiple previously active regional faults, as well as along newly identified faults. This VT seismicity is mainly distributed in a sector from the northwest to the east of the volcanic complex at distances of up to 30 km from the crater. We focus our analysis on two eruptive episodes: the eruption onset and subsequent crater migration from south to north, and the increase of lava dome extrusion rate in 2019. Both episodes are accompanied by seismic velocity decreases of up to 0.2% and are preceded by a few weeks by bursts of distal VT activity, including numerous repeating earthquakes. These repeated events were located on several remote tectonic faults (5-25 km from the vent). We suggest that these phenomena could be due to the injection of a batch of magma in the deep reservoir and/or conduit, which would generate 1) a pressure wave propagating in the hydrothermal system, triggering the bursts of seismic activity and 2) slow rising of magma by melting old material filling the conduit that eventually produced the eruptive and dome growth acceleration events.

This work proposes a new method to probe the hidden magmatic evolution of quiescent Andean volcanoes from the Pb isotope composition of gases. The method is based on an assimilation-fractional crystallisation-degassing model linking the Pb isotope composition of gases with the SiO2 content of their magmatic source. The model is applied to El Misti volcano that threatens Arequipa, the second most densely populated city of Peru. Gas condensates and Pb-rich solid deposits (PbS, PbCl2, PbSO4) collected in 2018 in the bottom of El Misti crater at 260–150°C fumarole vents were used to reconstruct the mean composition of degassing magmas (60.8–61.8 wt% SiO2). These compositions are slightly more evolved than the lavas from the last AD 1440–1470 eruption, suggesting either the secular differentiation of the main magma reservoir, or the contribution of more evolved magmas to volcanic gases. On the other hand, the slight but significant difference between the instantaneous composition recorded in gas condensates and the time-integrated composition recorded in solid deposits points to the degassing of less evolved magmas over the last decades. This trend is ascribed to a recent recharge of El Misti reservoir with hot mafic magmas, in agreement with the evolution of fumarolic deposit mineralogy in the last half a century. The Pb isotope composition of gas appears to be a promising tool for probing the hidden magmatic evolution of quiescent volcanoes where assimilation-fractional crystallisation operates.

To better understand the recent internal structure of Misti volcano, we determined a 3D S-wave velocity model applying Ambient Noise Tomography (ANT). We used data from 23 broadband and short-period seismic stations temporarily installed at Misti volcano between March and December 2011. This dataset allowed us to obtain empirical Green's functions by cross-correlating seismic ambient noise signals. Then, we retrieved 104 dispersion curves using the frequency-time analysis (FTAN) and, through a non-linear multiscale inversion, we obtained nine 2-D Rayleigh waves group velocity maps for periods in the range 0.7 s - 2 s. Finally, we carried out the depth inversion through a Bayesian transdimensional inversion to obtain a 3-D S-wave velocity model down to 3 km depth. Our study highlights five relevant seismic velocity anomalies. We observed the presence of three high-velocity zones located in the west-northwest, southwest and southeast parts of the crater, that could be related to intrusive bodies possibly associated with the formation of Misti volcano. We also observed two low-velocity anomalies in the volcano's western and central parts, which coincide with previous studies' findings and are related to fractured and weakened materials associated with the external caldera collapse and recent eruption episodes.

The Central Volcanic Zone of the Andes (CVZA) has been the focus of volcanological research for decades, becoming a very important site to understand a number of volcanic processes. Despite most of the research in the CVZA being carried out by foreign scientists, the last two decades have seen a significant increase in contributions by regional researchers. This surge has been facilitated by the creation of new volcanic observatories, improvement of the monitoring networks, creation of postgraduate programs where new local volcanologists are trained, creation of specialized research nuclei or groups, and increasing investment in research. This article presents a review of the evolution of the contributions of the regional volcanological community to the knowledge of the CVZA in the last 20 years (2000–2019), both from research and monitoring institutions in Peru, Bolivia, Argentina, and Chile. Based on updates made by the regional groups, a new list of active/potentially active volcanoes of the CVZA is presented, as is a complete database for article published on the CVZA. We find that a significant motivator has been regional volcanic unrest that has triggered new investment. Perú is the country with the highest investment in monitoring and research and is the best instrumented, Argentina is the country with the highest number of local participation in published papers in the domain of volcanology and magmatic systems, and Chilean volcanoes are the focus of the highest number of articles published. The current situation and general projections for the next decade (2020–2030) are also presented for each country, where we believe that the over the next 10 years, will be increased the monitoring and research capabilities, improved the scientific knowledge with more participation of regional institutions, and strengthen the collaboration and integrated work between CVZA countries, especially in border volcanoes.

We reconstruct the eruptive chronology of the Yucamane-Calientes compound volcano in southern Peru based on extensive fieldwork and a large dataset of geochronological (K-Ar, 40Ar/39Ar, U-Pb, and C-14) and geochemical (major and trace element) analyses. This compound volcano is composed of two edifices that have experienced discontinuous volcanic activity from the middle Pleistocene to the Holocene. The Calientes volcano has been constructed in four successive stages: Calientes I is composed of andesitic lava flows dated at similar to 500 ka. Subsequently, the Callazas ignimbrite (Calientesll stage) was emplaced similar to 160-190 ka, followed by the main cone-building stage (Calientes Ill) at similar to 130-100 ka. Finally, the Holocene Calientes domes were emplaced and represent the last eruptive products of this edifice. The Yucamane volcano has been constructed in three stages: Yucamane I consists of a succession of andesitic lava flows exposed at the base of the volcano that are older than 40 ka Yucamane II (similar to 36-30 ka) comprises a thick sequence of block-and-ash-flow deposits that represents an episode of dome growth predating the younger Yucamane cone (Yucamane built alter 20-25 ka During the Holocene, Yucamane vulcanian to sub-Plinian activity has emplaced tephra-fall and pyroclastic-density-current deposits. The most recent explosive eruptions occurred ca. 3000 BP and emplaced a tephra-fall and pumice-flow deposits. Most samples from Calientes volcano are andesites and dacites (60.1-67.7 wt% SiO2), while rocks from Yucamane volcano are basaltic-andesites to dacites (53.4-66.9 wt% SiO2). The rocks have a mineral assemblage of plagioclase, amphibole, biotite, orthopyroxene, clinopyroxene, olivine, and Fe-Ti oxides. The analyzed samples are categorized within a high-K, talc-alkaline series. Calientes volcano erupted mostly andesitic magmas, but its history is punctuated by rare eruptions of silica-rich magmas. In contrast, Yucamane volcano follows a different trend characterized by a gradual decrease in silica content through post-glacial time, from the large (VEI 3) sub-Plinian andesitic eruption of similar to 3 ka to moderate (VEI <= 2) vulcanian eruptions of basaltic-andesitic. On the basis of such recurrent and recent (Holocene), low-to-moderate explosive activity, Yucamane must be considered an active and potentially threatening volcano, which may affect the province of Candarave with similar to 8000 inhabitants. (C) 2020 Elsevier B.V. All rights reserved.

Understanding the links between the magma differentiation processes, the magma plumbing system and the magma composition at arc volcanoes is of paramount importance for volcanic hazard assessment. In this work we focus on the post-glacial, Holocene, historical, and recent eruption products of Ubinas volcano (Peru), which display an overall decrease in silica content from the older, plinian (VEI 3-5), rhyolitic eruptions (69-71 wt% SiO2) to the historical and recent (2006-2009, 2013-2017), vulcanian (VEI 1-2) basaltic andesitic eruptions (55-57 wt% SiO2). Based on a comprehensive study of the major and trace elements and the Sr-NdPb isotopes, we conclude that this temporal pattern reflects the evolution of the Ubinas magmas in the middle-to-upper crust by a coupled Assimilation-Fractional Crystallization (AFC) process involving a cumulate composed of plagioclase, amphibole, clinopyroxene, orthopyroxene and Fe-Ti oxides, with minor amounts of olivine and biotite at the mafic and felsic end-members, respectively. Upper crustal assimilation is limited to 5-8 vol%, but the overall radiogenic Sr-Nd-Pb signature of the Ubinas magmas requires a larger crustal component, which must therefore occur at middle to lower crustal depths. The petrology of the Ubinas magmas also points to an overall increase in P-T conditions: the large Holocene dacitic and rhyolitic eruptions record temperatures ranging from 800 to 850 degrees C and pressures in the range of 200-400 MPa, whereas the historical and recent (2006-2009, 2013-2017) basaltic andesitic eruptions provide higher temperatures and pressures (1000 degrees C, >300-400 MPa). Overall, the thermo-barometry, phase equilibrium and geochemical constraints allow us to pro pose the existence of a middle-to-upper crust magma column composed of a highly crystalline magma mush containing batches of liquid magma, which seems to be continually recharged from deeper levels. On the basis of the petrological nature of the historical basaltic andesitic eruptions (1667 CE, 2006-2009, 2013-2017), we postulate that during the last centuries, Ubinas experienced a recharge-dominated process, with no evidence for a rejuvenation of the silica-rich reservoir that fed the large Holocene dacitic to rhyolitic eruptions. This study highlights the importance of detailed petrological studies of Holocene sequences at explosive arc volcanoes in order to constrain the magmatic processes and conditions that control large explosive eruptions. (C) 2020 Elsevier B.V. All rights reserved.

Ubinas volcano has produced moderate explosive eruptions during the last ~500 years. With 26 eruptive periods, this composite cone is the most active volcano in Peru. The 2006–2009 and 2013–2017 eruptions impacted people, agriculture, and livestock within 15 km of the vent. On 24 June 2019 a new eruptive cycle started with minor emissions of tephra and aerosols. Activity increased on July 19 with an explosion beginning at 2:30 AM (local time). At that time, seismicity also increased with a predominance of LP-type signals. Two clearly differentiated and wind-controlled volcanic plumes were observed. Initially, the plume reached 6500 m above the summit and the main dispersion axis was ESE, dispersing ash as far as 300 km away to the villages of Jesús de Machaca and Catacora, Bolivia, where ash fall disrupted people’s daily activities. While the first plume was still active, a 1200-m-high secondary plume developed and was dispersed to the SE, reaching more than 200 km away into the Tacna region (Peru). After July 19, the SO2 emission rate increased reaching 9600 TN/day on July 23. The tephra fall on July 19 and gas emissions forced Civil Defense authorities to subsequently evacuate residents living in the valleys around Ubinas within 15 km of the volcano. Just after the tephra fall on July 19, deposit thickness was measured along the secondary dispersion axis, where the nearest populated and most impacted areas are located. The accumulation of lapilli and ash during the July 19 eruption reached 7 mm in the village of Ubinas, 5 mm in Tonohaya, 4 mm in San Miguel, 3 mm in Escacha and Huatagua, 2 mm in Huarina and 1 mm in Matalaque, ~20 km away. Fine ash accumulation was also reported at the Quellaveco mine, 90 km to the SE. Samples collected at 3.2 and 6 km from the vent allowed three types of juvenile clasts to be differentiated; dark- and light-gray scoria and dense, dark-gray lithics. Some juvenile clasts have bands of dark and light material, suggesting a partial mixing (mingling) of compositionally different magmas, which might have triggered the eruption. Based on the variety of juvenile clasts and unprecedented SO2 emission rates compared to the two past eruptive periods, we expect stronger eruptive activity or at least a long-lasting eruptive cycle.

El Misti is one of active volcanos in Peru, and known because it is located close to an important city of Arequipa, at about 17 km. There has been in the past several eruptions and the volcano is covered with lava, ash, etc. from such eruptions. The edifice is composed of a stratotocone called Misti 1, two stratocones designated Misti 2 and Misti 3 and a summit cone Misti 4. In this work samples from Misti 3 have been collected for TL dating. In the past charcol has been used for radiocarbon measurements and found age varying from 25000 to 35000 years. The TL dating produces ages between 28700 and 32300 years.