Sabancaya Volcano Research Articles

Near-real-time multiparametric seismic and visual monitoring of explosive activity at Sabancaya volcano, Peru

This study presents the development of a multiparametric system that utilizes artificial intelligence techniques to identify and analyze volcanic explosions in near real-time. The study analyzed 1343 explosions recorded between 2019 and 2021, along with seismic, meteorological, and visible image data from the Sabancaya volcano. Deep learning algorithms like the U-Net convolutional neural network were used to segment and measure volcanic plumes in images, while boosting-based machine learning ensembles were used to classify seismic events related to ash plumes. The findings demonstrate that these approaches effectively handle large amounts of data generated during seismic and eruptive crises. The U-Net network achieved precise segmentation of volcanic plumes with over 98% accuracy and the ability to generalize to new data. The CatBoost classifier achieved an average accuracy of 94.5% in classifying seismic events. These approaches enable the real-time estimation of eruptive parameters without human intervention, contributing to the development of early warning systems for volcanic hazards. In conclusion, this study highlights the feasibility of using seismic signals and images to detect and characterize volcanic explosions in near real-time, making a significant contribution to the field of volcanic monitoring.

Unraveling the Complex Interplay: Exploring the Relationships between Seismic and Volcanic Activities in the Colca River Area Using the Coulomb Stress Transfer

Abstract The Colca River area is affected by shallow small-to-moderate earthquakes due to the activity of normal and strike-slip crustal faults on the overriding South American plate. In addition, volcanic activity from the Sabancaya volcano has been recorded. However, the complex relationship between seismic and volcanic activities and the factors that trigger them are poorly understood. To better understand the factors that influence seismic and volcanic activity and their potential connection, it is crucial to characterize the interactions between subsequent earthquakes and assess the impact of magmatic inflation on seismic events. In this study, we analyzed the static Coulomb stress transfer caused by the selected largest earthquakes from 1991 to 2022. We focused on both the assumed source faults and the receiver faults. Furthermore, we examined the Coulomb stress change due to magmatic inflation in 2013–2022 on nodal planes of the selected earthquakes. The results confirm the tectonic source for most earthquakes in the Colca region. Commonly, the magmatic source enhanced the stress change induced by the tectonic source. Although the Coulomb stress change caused by the significant earthquakes had a greater impact than the one resulting from the magmatic inflation, the Coulomb stress transfer seems not to be a dominant factor determining the occurrence and location of earthquakes in this area. The results indicate that most source faults of the analyzed earthquakes were not brought closer to failure due to a positive Coulomb stress transfer caused by seismic activity or magmatic inflation.

Image analysis of volcanic plumes: A simple calibration tool to correct for the effect of wind

Video cameras provide vital information on volcanic plumes from explosive eruptions, such as plume height, for monitoring and research. These images must be calibrated to get accurate quantitative data. However, the presence of wind complicates any calibration as the plume may no longer lie in the image plane, i.e. a plane perpendicular to the camera’s line-of-sight. Here, we present a simple new tool to correct for the effect of wind on the position and height of a volcanic plume as determined from imagery by rotating the image plane to be in the direction of the wind. We show the importance of accounting for the effect of wind on the maximum plume height determined from videos for two case-studies; a Vulcanian explosion from Sabancaya volcano, Peru, and a sustained plume from Mount Etna, Italy. This tool can improve the accuracy of quantitative information extracted from images of volcanic plumes, and should prove useful for both research and monitoring purposes.

Tracking Eruption Column Thermal Evolution and Source Unsteadiness in Ground‐Based Thermal Imagery Using Spectral‐Clustering

AbstractVolcanic eruption columns typically have unsteady source conditions, where mass and heat fluxes from the vent evolve or fluctuate on time scales from seconds to hours. However, integral plume models routinely assume source conditions that are statistically stationary, and the degree to which source unsteadiness influences the mechanics of column rise and air entrainment has not been established with quantitative predictions. We address this knowledge gap by examining eruptions with varying unsteady character at Sabancaya Volcano, Peru. Using a novel tracking algorithm based on spectral clustering, we track the spatiotemporal evolution of coherent turbulent structures in columns using ground‐based, thermal infrared imagery. For turbulent structures tracked in time and space, we calculate the power law decay exponent of excess temperature with height. In general, the starting pulses of transient events are characterized by power law exponents matching theoretical predictions for an instantaneous point release of buoyancy (i.e., a thermal), which evolve with sustained emissions to values consistent with steady plumes. Our results support previous findings from field evidence and laboratory experiments that entrainment and gravitational stability in unsteady volcanic columns are inadequately captured by time‐averaging or constant entrainment coefficients. We propose a quantitative definition for column source unsteadiness which captures the timing and magnitude of source fluctuations on time scales that influence entrainment mechanics, and which provisionally predicts our observed differences in power law behavior. We argue for systematic experimental and numerical studies of the relationship between source unsteadiness and entrainment to implement unsteady entrainment parameterizations for integral plume models.

The post-2016 long-lasting Vulcanian activity of Sabancaya volcano (Peru) and associated aeolian remobilisation of volcanic ash

The characterisation of tephra deposits resulting from almost simultaneous sedimentation and wind remobilisation is complex, and multidisciplinary strategies are required in order to accurately constrain associated processes and eruptive parameters. We present a multifaceted study that aims to characterise the recent eruptive activity and the subsequent aeolian remobilisation of tephra deposits at Sabancaya volcano (Peru), which started erupting in November 2016 with frequent and relatively small explosions (plume heights <6 km above the vent). First, we estimated the bulk volume of tephra deposit produced between November 2016 and August 2018 at 0.04 ± 0.02 km3, and the dense rock equivalent (DRE) volume at 0.02 ± 0.01 km3. This corresponds to a tephra production rate of 1.1 ± 0.5 × 10−3 km3 DRE per month. Second, continuous sampling in a dedicated tephra collector network between April 2018 and November 2019 allowed estimation of the tephra volume at 2.3 ± 1.1 × 10−5 km3 DRE per month, indicating a significant decrease in the mass eruption rate since 2018. Third, by characterising the pulsatory activity through the repose interval between explosions and magma characteristics, Sabancaya's activity was classified as Vulcanian. Finally, aeolian remobilisation phenomena were studied using high-resolution videos, measurements of the airborne concentration of particulate matter with a diameter of ≤10 μm (PM10) and particle physical characterisation. Subtle morphological differences are identified between remobilised particles and those in primary deposits, and we found that particles moving at ground level and above 1.5 m have grainsizes transportable by saltation and suspension, respectively.

The role of ancestral practices as social capital to enhance community disaster resilience. The case of the Colca Valley, Peru

Mitigating the gap between disaster risk management planning by government agencies and the perception and adaptation to risk of local communities is currently challenging. Numerous studies have generated knowledge based on the value of community actions and increased resilience. This research aims to analyze the role of ancestral Andean practices in building community resilience in settlements exposed to volcanic risk. The methodology is based on the combination of quantitative methods, survey and qualitative methods, focus groups, and interviews. The case study is the Colca Valley in Arequipa, specifically the villages which were affected by the eruption of the Sabancaya volcano and by collateral seismic effects. The results support knowledge regarding risk management in Andean communities, in addition to reflecting on 4 findings related to the validity of ancestral networks and practices, the lack of community trust regarding the government's response capacity, the differences between the perception of risk according to the activities that are carried out within the same community, and the existence of different perceptions of risk according to the location of the communities.

The 2013–2020 seismic activity at Sabancaya Volcano (Peru): Long lasting unrest and eruption

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.

PlumeTraP: A New MATLAB-Based Algorithm to Detect and Parametrize Volcanic Plumes from Visible-Wavelength Images

Tephra plumes from explosive volcanic eruptions can be hazardous for the lives and livelihoods of people living in the proximity of volcanoes. Monitoring and forecasting tephra plumes play essential roles in the detection, characterization and hazard assessment of explosive volcanic events. However, advanced monitoring instruments, e.g., thermal cameras, can be expensive and are not always available in monitoring networks. Conversely, visible-wavelength cameras are significantly cheaper and much more widely available. This paper proposes an innovative approach to the detection and parametrization of tephra plumes, utilizing videos recorded in the visible wavelengths. Specifically, we have developed an algorithm with the objectives of: (i) identifying and isolating plume-containing pixels through image processing techniques; (ii) extracting the main geometrical parameters of the eruptive column, such as the height and width, as functions of time; and (iii) determining quantitative information related to the plume motion (e.g., the rise velocity and acceleration) using the physical quantities obtained through the first-order analysis. The resulting MATLAB-based software, named Plume Tracking and Parametrization (PlumeTraP), semi-automatically tracks the plume and is also capable of automatically calculating the associated geometric parameters. Through application of the algorithm to the case study of Vulcanian explosions from Sabancaya volcano (Peru), we verify that the eruptive column boundaries are well recognized, and that the calculated parameters are reliable. The developed software can be of significant use to the wider volcanological community, enabling research into the dynamics of explosive volcanic eruptions, as well as potentially improving the use of visible-wavelength cameras as part of the monitoring networks of active volcanoes. Furthermore, PlumeTraP could potentially find a broader application for the analysis of any other plume-shaped natural or anthropogenic phenomena in visible wavelengths.

Shallow magma convection evidenced by excess degassing and thermal radiation during the dome-forming Sabancaya eruption (2012\u20132020)

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.

Identifying source regions of air masses sampled at the tropical high-altitude site of Chacaltaya using WRF-FLEXPART and cluster analysis

Abstract. Observations of aerosol and trace gases in the remote troposphere are vital to quantify background concentrations and identify long-term trends in atmospheric composition on large spatial scales. Measurements made at high altitude are often used to study free-tropospheric air; however such high-altitude sites can be influenced by boundary layer air masses. Thus, accurate information on air mass origin and transport pathways to high-altitude sites is required. Here we present a new method, based on the source–receptor relationship (SRR) obtained from backwards WRF-FLEXPART simulations and a k-means clustering approach, to identify source regions of air masses arriving at measurement sites. Our method is tailored to areas of complex terrain and to stations influenced by both local and long-range sources. We have applied this method to the Chacaltaya (CHC) GAW station (5240 m a.s.l.; 16.35∘ S, 68.13∘ W) for the 6-month duration of the “Southern Hemisphere high-altitude experiment on particle nucleation and growth” (SALTENA) to identify where sampled air masses originate and to quantify the influence of the surface and the free troposphere. A key aspect of our method is that it is probabilistic, and for each observation time, more than one air mass (cluster) can influence the station, and the percentage influence of each air mass can be quantified. This is in contrast to binary methods, which label each observation time as influenced by either boundary layer or free-troposphere air masses. Air sampled at CHC is a mix of different provenance. We find that on average 9 % of the air, at any given observation time, has been in contact with the surface within 4 d prior to arriving at CHC. Furthermore, 24 % of the air has been located within the first 1.5 km above ground level (surface included). Consequently, 76 % of the air sampled at CHC originates from the free troposphere. However, pure free-tropospheric influences are rare, and often samples are concurrently influenced by both boundary layer and free-tropospheric air masses. A clear diurnal cycle is present, with very few air masses that have been in contact with the surface being detected at night. The 6-month analysis also shows that the most dominant air mass (cluster) originates in the Amazon and is responsible for 29 % of the sampled air. Furthermore, short-range clusters (origins within 100 km of CHC) have high temporal frequency modulated by local meteorology driven by the diurnal cycle, whereas the mid- and long-range clusters' (&gt;200 km) variability occurs on timescales governed by synoptic-scale dynamics. To verify the reliability of our method, in situ sulfate observations from CHC are combined with the SRR clusters to correctly identify the (pre-known) source of the sulfate: the Sabancaya volcano located 400 km north-west from the station.

Monitoring of active volcanoes in Peru by the Instituto Geofísico del Perú

Volcano monitoring in Peru is carried out by the Instituto Geofísico del Perú (IGP), through its Centro Vulcanológico Nacional (CENVUL). CENVUL monitors 12 out of 16 volcanoes considered as historically active and potentially active in southern Peru and issues periodic bulletins about the volcanic activity and, depending on the alert-level of each volcano, also issues alerts and warnings of volcanic unrest, ash dispersion, and the occurrence of lahars. The information generated by CENVUL is disseminated to the civil authorities and the public through different information media (newsletters, e-mail, website, social media, mobile app, etc.). The IGP volcanology team was formed after the eruption of Sabancaya volcano in 1988. Since then, geophysical and geological studies, volcanic hazards assessments, and multidisciplinary monitoring realized by the IGP, have provided a comprehensive understanding of volcanic activity in Peru and forecast future eruptive scenarios. Currently, 80% of the historically active and potentially active volcanoes in Peru are equipped with networks of multiparameter instruments, with the seismic monitoring being the most widely implemented. In this report, we present the situation of volcanic monitoring in Peru, the monitoring networks, the techniques employed, as well as efforts to educate and inform the public and officials responsible for disaster risk management.

Source Model for Sabancaya Volcano Constrained by DInSAR and GNSS Surface Deformation Observation

Sabancaya is the most active volcano of the Ampato-Sabancaya Volcanic Complex (ASVC) in southern Perú and has been erupting since 2016. The analysis of ascending and descending Sentinel-1 orbits (DInSAR) and Global Navigation Satellite System (GNSS) datasets from 2014 to 2019 imaged a radially symmetric inflating area, uplifting at a rate of 35 to 50 mm/yr and centered 5 km north of Sabancaya. The DInSAR and GNSS data were modeled independently. We inverted the DInSAR data to infer the location, depth, and volume change of the deformation source. Then, we verified the DInSAR deformation model against the results from the inversion of the GNSS data. Our modelling results suggest that the imaged inflation pattern can be explained by a source 12 to 15 km deep, with a volume change rate between 26 × 106 m3/yr and 46 × 106 m3/yr, located between the Sabancaya and Hualca Hualca volcano. The observed regional inflation pattern, concentration of earthquake epicenters north of the ASVC, and inferred location of the deformation source indicate that the current eruptive activity at Sabancaya is fed by a deep regional reservoir through a lateral magmatic plumbing system.

Volcano‐Tectonic Interactions at Sabancaya Volcano, Peru: Eruptions, Magmatic Inflation, Moderate Earthquakes, and Fault Creep

AbstractWe present evidence of volcano‐tectonic interactions at Sabancaya volcano that we relate to episodic magma injection and high regional fluid pore pressures. We present a surface deformation time series at Sabancaya including observations from ERS‐1/2, Envisat, Sentinel‐1, COSMO‐SkyMed, and TerraSAR‐X that spans June 1992 to February 2019. These data show deep‐seated inflation northwest of Sabancaya from 1992–1997 and 2013–2019, as well as creep and rupture on multiple faults. Afterslip on the Mojopampa fault following a 2013 MW 5.9 earthquake is anomalously long lived, continuing for at least 6 years. The best fit fault plane for the afterslip is right‐lateral motion on an EW striking fault at 1 km depth. We also model surface deformation from two 2017 earthquakes (MW 4.4 and MW 5.2) on unnamed faults, for which the best fit models are NW striking normal faults at 1–2 km depth. Our best fit model for a magmatic inflation source (13 km depth, volume change of 0.04 to 0.05 km3 yr−1) induces positive Coulomb static stress changes on these modeled fault planes. Comparing these deformation results with evidence from satellite thermal and degassing data, field observations, and seismic records, we interpret strong pre‐eruptive seismicity at Sabancaya as a consequence of magmatic intrusions destabilizing tectonic faults critically stressed by regionally high fluid pressures. High fluid pressure likely also promotes fault creep driven by static stress transfer from the inflation source. We speculate that combining high pore fluid pressures with sufficiently large, offset magmatic inflation can promote strong earthquakes during volcanic unrest.

Degassing at Sabancaya volcano measured by UV cameras and the NOVAC network

We used low-cost Raspberry Pi ultraviolet (UV) cameras to measure sulphur dioxide (SO2) fluxes from Sabancaya volcano, Peru, during eruptive activity on 27 April 2018. Light dilution corrections were made by operating instruments at two distances simultaneously. Estimated SO2 fluxes of 27.1 kgs-1 are higher than previously reported, likely due to the current eruptive episode (ongoing since November 2016). Each eruptive event included frequent (2–3 per minute), ash-rich emissions, forming gas pulses with masses of 3.0–8.2 tonnes SO2. Sustained degassing and lack of overpressure suggest open-vent activity. Mean fluxes are consistent with those measured by a permanent NOVAC station (25.9 kgs-1) located under the plume, with remaining differences likely due to windspeed estimates and sampling rate. Our work highlights the importance of accurate light dilution and windspeed modelling in SO2 retrievals and suggests that co-location of UV cameras with permanent scanning spectrometers may be valuable in providing accurate windspeeds.

Can Water Vapor Help Forecast When a Volcano Will Blow?

A widely used technique to monitor sulfur dioxide was tweaked to focus on water vapor at Peru’s Sabancaya Volcano. Results show that the volcano steamed up prior to its 2016 eruption.

Remote measurement of high preeruptive water vapor emissions at Sabancaya volcano by passive differential optical absorption spectroscopy

AbstractWater (H2O) is by far the most abundant volcanic volatile species and plays a predominant role in driving volcanic eruptions. However, numerous difficulties associated with making accurate measurements of water vapor in volcanic plumes have limited their use as a diagnostic tool. Here we present the first detection of water vapor in a volcanic plume using passive visible‐light differential optical absorption spectroscopy (DOAS). Ultraviolet and visible‐light DOAS measurements were made on 21 May 2016 at Sabancaya Volcano, Peru. We find that Sabancaya's plume contained an exceptionally high relative water vapor abundance 6 months prior to its November 2016 eruption. Our measurements yielded average sulfur dioxide (SO2) emission rates of 800–900 t/d, H2O emission rates of around 250,000 t/d, and an H2O/SO2 molecular ratio of 1000 which is about an order of magnitude larger than typically found in high‐temperature volcanic gases. We attribute the high water vapor emissions to a boiling‐off of Sabancaya's hydrothermal system caused by intrusion of magma to shallow depths. This hypothesis is supported by a significant increase in the thermal output of the volcanic edifice detected in infrared satellite imagery leading up to and after our measurements. Though the measurement conditions encountered at Sabancaya were very favorable for our experiment, we show that visible‐light DOAS systems could be used to measure water vapor emissions at numerous other high‐elevation volcanoes. Such measurements would provide observatories with additional information particularly useful for forecasting eruptions at volcanoes harboring significant hydrothermal systems.

Deformation and seismicity near Sabancaya volcano, southern Peru, from 2002 to 2015

AbstractWe use interferometric synthetic aperture radar (InSAR) and local seismic data to investigate the cause of earthquake sequences near Sabancaya volcano in southern Peru from 2002 to 2014, with a particular focus on events leading up to the August 2014 phreatic eruption. InSAR‐observed deformation associated with earthquake swarms in late 2002, February 2013, and July 2013 is modeled by fault slip, with no need for magmatic sources to explain the deformation. The majority of the seismicity is an expression of the regional tectonic system, which is characterized by E‐W trending normal faults, but a link to the magmatic system is possible. The Mw 5.9 earthquake on 17 July 2013 occurred on a previously unmapped normal fault that continued to deform in the months following the earthquake. An increase in long period and hybrid seismicity and changes in fumarolic emissions in 2013–2014 culminating in the August 2014 eruption indicates the involvement of both tectonic and magmatic systems.

Environmental records from temperate glacier ice on Nevado Coropuna saddle, southern Peru

Abstract. We investigated past climate variability and the zonal short and long-range transport of air masses in tropical South America using chemical, isotopic and palynological signals from a 42 m-long ice core recovered in 2003 from the saddle of the Nevado Coropuna, southern Peru (72°39´ W; 15°32´ S; 6080 m a.s.l.). We found that precipitation at this site depends mainly on the easterly circulation of air masses originated from the tropical Atlantic Ocean. Nevertheless, sporadic Pacific air masses arrivals, and strong cold waves coming from southern South America reach this altitude site. In spite of post-depositional effects, we were able to identify two strong ENSO (El Niño-Southern Oscillation) event signatures (1982–1983 and 1992) and the eruptive activity of the nearby Sabancaya volcano (1994).

An InSAR‐based survey of volcanic deformation in the central Andes

We extend an earlier interferometric synthetic aperture radar (InSAR) survey covering about 900 remote volcanos of the central Andes (14°–27°S) between the years 1992 and 2002. Our survey reveals broad (10s of km), roughly axisymmetric deformation at 4 volcanic centers: two stratovolcanoes are inflating (Uturuncu, Bolivia, and Hualca Hualca, Peru); another source of inflation on the border between Chile and Argentina is not obviously associated with a volcanic edifice (here called Lazufre); and a caldera (Cerro Blanco, also called Robledo) in northwest Argentina is subsiding. We explore the range of source depths and volumes allowed by our observations, using spherical, ellipsoidal and crack‐like source geometries. We further examine the effects of local topography upon the deformation field and invert for a spherical point‐source in both elastic half‐space and layered‐space crustal models. We use a global search algorithm, with gradient search methods used to further constrain best‐fitting models. Inferred source depths are model‐dependent, with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure. Source depths relative to sea level are: 8–18 km at Hualca Hualca; 12–25 km for Uturuncu; 5–13 km for Lazufre, and 5–10 km at Cerro Blanco. Deformation at all four volcanoes seems to be time‐dependent, and only Uturuncu and Cerro Blanco were deforming during the entire time period of observation. Inflation at Hualca Hualca stopped in 1997, perhaps related to a large eruption of nearby Sabancaya volcano in May 1997, although there is no obvious relation between the rate of deformation and the eruptions of Sabancaya. We do not observe any deformation associated with eruptions of Lascar, Chile, at 16 other volcanoes that had recent small eruptions or fumarolic activity, or associated with a short‐lived thermal anomaly at Chiliques volcano. We posit a hydrothermal system at Cerro Blanco to explain the rate of subsidence there. For the last decade, we calculate the ratio of the volume of magma intruded to extruded is between 1–10, and that the combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate.

Evolved lavas on Mars? Observations from southwest Arsia Mons and Sabancaya volcano, Peru

An extensive (106 km2) lava flow field SW of Arsia Mons contains individual lobes that are 102–103 km long, are ∼65 m thick, and display a surface ridging similar to the textures found on terrestrial andesite, dacite, and rhyolite flows, raising the question of whether large‐volume evolved lava flows exist on Mars. The regularly spaced ridges on these Martian flows have wavelengths of ∼100 ± 34 and amplitudes of ∼27 ± 11 m. An andesitic lava flow field at Sabancaya volcano, Peru, is a morphologic analog, with flow thicknesses of ∼60–170 m and surface ridges. One intensely studied flow lobe at Sabancaya has a ridge wavelength of ∼67 ± 24 m and amplitude of ∼5 ± 2 m. Despite morphologic similarities, comparing the calculated rheologic and emplacement parameters of the two lava flow fields reveals large differences. Calculated yield strengths for the Martian lavas are 103 Pa; those for lavas of Sabancaya, Peru, are 105 Pa. Effusion rates of 103–104 m3 s−1 calculated for the Martian flows are larger than those calculated for the Sabancaya lavas (1 m3 s−1). Calculations of emplacement times for the Martian and Sabancaya flows are 1–102 days and 1–103 days, respectively. Estimates of viscosity are 104–106 Pa s for southwestern Arsia Mons and 1010–1012 Pa s for Sabancaya. We therefore conclude that the flows southwest of Arsia Mons are most likely not the same composition as those at Sabancaya volcano, but rather are basaltic or basaltic andesite in composition.