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Deception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica, with more than 20 explosive eruptive events registered over the past few centuries. Recent eruptions (1967, 1969, and 1970) and volcanic unrest episodes (1992, 1999, and 2014–2015) demonstrate that volcanic activity will likely occur in the future. Despite this, there has been a considerable increase in the number of scientific bases, tourist activities and air and vessel traffic in the region during the last several decades. The escalation in interest has increased the amount of infrastructure and population numbers exposed to a future eruption. Thus, there is an urgent need to develop an accurate long-term assessment of the volcanic hazard of the island. However, past attempts have always been limited by the incompleteness of the eruptive record. Volcanic ash layers found in marine and lacustrine sediment cores and glaciers outside Deception Island are a fundamental source of information for reconstructing the explosive eruptive record of the volcano. The spatial distribution of the tephra layers, as well as their physicochemical analysis are invaluable for determining the size and explosiveness of past eruptive events, as well as for assessing the extent and impact of their related hazards (e.g., ash fall out). In order to overcome the dispersion of existing data among numerous publications and to facilitate the analysis of available information on tephra layers sourced in Deception Island, we present the DecTephra (Deception Island Tephra Record) database. The current database version contains 362 tephra layers (including cryptotephras) located at sites up to 3115 km distant from the island. For each tephra layer, the database includes: (i) the location and simple description of the sampling site; and (ii) the key petrologic and geochemical features of each tephra layer. A preliminary analysis of the information contained in the DecTephra database (e.g., magma composition, explosiveness, eruptive recurrence, etc.), validates it as a key tool for evaluating past explosive activity of the volcano. In addition, it can function as a valuable resource for paleoenvironmental and paleoclimatic studies requiring tephrostratigraphical and tephrochronological control at local and regional scales. DecTephra also has the potential to help to assess the contribution of volcanic forcing to Holocene climate variability in the Southern Hemisphere., This research was supported by MINECO projects VOLCLIMA (CGL2015-72629-EXP), VOLGASDEC (PGC2018-095693-B-I00) (AEI/FEDER, EU) and the MCIN/AEI/10.13039/501100011033 grant HYDROCAL (PID2020-114876GB-I00). A.G. is grateful for her Ramón y Cajal contract (RYC-2012-11024), A.M.A-V for the grant under the “JSPS invitation fellowship” program (S18113) and A.P·S is grateful for his PhD grant “Programa Propio III Universidad de Salamanca co-funded by Banco de Santander” and his JAE_Intro scholarship (JAEINT_20_00670). This research is part of POLARCSIC and PTI VOLCAN activities. We are grateful to Grant George Buffett (TERRANOVA SCIENTIFIC; www.terranova.barcelona) for English editing of an early draft of this paper.

Deception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica, with more than 20 explosive eruptive events registered over the past centuries. Recent eruptions (1967, 1969, and 1970) and volcanic unrest episodes (1992, 1999, and 2014–2015) demonstrate that volcanic activity is likely occurring in the future. This is of special concern for scientists, logistic personnel, and tourists, since the South Shetland Islands are an important tourist destination and host numerous year-round and seasonal scientific stations and base camps. Significant efforts have been made to understand the complex magmatic and volcanic evolution of Deception Island with special interest on its subaerial part. However, studies on submerged volcanic cones within Port Foster, the sea-flooded part of Deception Island's caldera depression, are comparatively scarce. Here, we provide a full characterization of Stanley Patch volcano, the largest of these volcanic edifices. Estimated morphometric parameters based on new multibeam bathymetric data, supported by petrographic and chemical observations from rock samples collected on the crater rim, reveal that Stanley Patch volcano grew in a subaerial environment. This result, combined with previous findings and new sedimentological evidence from our ultra-high resolution seismic profiles, allow to further detail the island's geologic evolution since the caldera collapse. We conclude that the complete flooding of Port Foster could have only occurred after the formation of Stanley Patch volcano, i.e. during the last ~2000 years, and in a time period of a few days or less., This research was supported by the Spanish Government RECALDEC (CTM2009-05919-E/ANT), PEVOLDEC (CTM2011-13578-E/ANT), POSVOLDEC (CTM2016-79617-P)(AEI/FEDER, UE), VOLGASDEC (PGC2018-095693-B-I00), USAL-2019 project (Programa Propio - mod. 1B) and the GALIEO-IHM Program. A.G. is grateful for her Ramón y Cajal contract (RYC-2012-11024), and A.M.A-V for the grant under the “JSPS invitation fellowship” program (S18113). D.P. is grateful for his Beatriu de Pinós (2016 BP 00086) and Juan de la Cierva (IJCI-2016-30482) contracts. We thank all the military staff of the Spanish Antarctic Base “Gabriel de Castilla”, BIO Hespérides oceanographic cruise and the Marine Hydrographic Institute, for their constant help and logistic support. This research is part of POLARCSIC and PTI VOLCAN activities. English editing by Grant George Buffett (www.terranova.barcelona). We thank the Editor, J.L. Macías, and both reviewers A. Di Roberto and P. Nomikou for their constructive comments that have allowed improving a previous version of this manuscript., This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S) to ICM-CSIC

Parent–offspring conflict theory predicts that offspring seek to prolong the parental care period, while parents strive to shorten it as much as possible. Transition to the crèche phase in penguins involves changes in the dynamic of parental investment in chicks, and thus may be modulated by interests that benefit parent or offspring. We explored parent–offspring interactions in the Chinstrap Penguin (Pygoscelis antarctica) to understand the influence such interactions would have on transition to crèche phase. We studied the effect of hatching date, nestling age, brood size, and nest location on parent–offspring interactions and the length of the guard phase. All behavioral variables related to nestling demands for parental investment increased as well as parental aggression towards their chicks, with increased nestling age. Brood size showed significant effects on both nestling and parental behavior. Hatching date was negatively correlated with the age at crèche. Consequently, the decision to leave the chicks unguarded seemed to be more based on the condition of adults rather than of the chicks. Given the short time available for breeding in Antarctica and that penguins are long-lived birds with several opportunities to breed, there may be conflicting selective factors between investment in feeding chicks versus extending the period of resource acquisition and storage prior to moult., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.

Increased thermal activity was detected to coincide with the onset of volcano inflation in the seawater-filled caldera at Deception Island. This thermal activity was manifested in pulses of high water temperature that coincided with ocean tide cycles. The seawater temperature anomalies were detected by a thermometric sensor attached to the tide gauge (bottom pressure sensor). This was installed where the seawater circulation and the locations of known thermal anomalies, fumaroles and thermal springs, together favor the detection of water warmed within the caldera. Detection of the increased thermal activity was also possible because sea ice, which covers the entire caldera during the austral winter months, insulates the water and thus reduces temperature exchange between seawater and atmosphere. In these conditions, the water temperature data has been shown to provide significant information about Deception volcano activity. The detected seawater temperature increase, also observed in soil temperature readings, suggests rapid and near-simultaneous increase in geothermal activity with onset of caldera inflation and an increased number of seismic events observed in the following austral summer.

Tephra layers preserved in lake sedimentary sequences provide valuable isochrons with which to synchronise palaeoclimatic records. However, in regions where tephra inputs are dominated by a single volcanic source, overlapping chemical compositions can preclude unambiguous correlation of tephra layers. In this study, we characterise multiple visible (macrotephra) layers within sedimentary sequences from three lakes in Byers Peninsula, Antarctica. By combining compositional analyses with additional constraints from textural componentry, we identify three distinct tephra isochrons—T1, T2, and T3—each with distinct textural properties. The relative proportion of glassy compared to crystal-rich grains varies from ~ 50% (T3) to ~ 3% (T1) of the total sample. Although the proportion of dense to vesicular grains differs only slightly between all sampled tephra layers, the dominant vesicle shape varies from spherical (T3) to irregular and polylobate (T1/T2). These textural differences can be related to variations in the eruptive processes occurring at the Deception Island source volcano. This study highlights the efficacy of a correlative approach based on both chemical and physical tephra properties for deconvolving the tephra stratigraphy in regions where chemical compositions are non-unique., Field work in Limnopolar Lake was supported by grant POL2006-06635/CGL from the Education and Culture Ministry (Spain) in the framework of the International Polar Year 2007-09 activities. AG is grateful for her Juan de la Cierva Grant (JCI-2010-06092) and Ramón y Cajal contract (RYC-2012-11024). Part of this research was supported by the MICINN grant CTM2011-13578-E.

This study aims at understanding the spatial distribution and characteristics of the frozen and unfrozen terrain in an alluvial fan on Deception Island, which is an active strato-volcano located in the Bransfield Strait (South Shetland Islands) with recent eruptions in 1967, 1969 and 1970. The alluvial fan is dominated by debris-flow, run-off and rock fall processes and permafrost occurs in several parts in the vicinity of anomalous geothermal heat flux. The aim is to assess the ways volcanic activity controls permafrost development and associated geomorphic dynamics using shallow subsurface, surface and air temperature measurements as well as thaw depth and electrical resistivity tomography (ERT) surveys.Results show a temperature increase with depth in the lower part of the fan reaching 13. °C at 0.80. m depth, without the presence of permafrost. The shallow borehole located at this site showed a stable thermal stratification all year-round, with only the upper 0.20. m reacting to meteorological forcing. In the upper part of the alluvial fan and debris cones, c. 100. m from the coast, frozen ground is present at c. 0.70. m depth. There, the shallow borehole shows a good coupling with air temperatures and the thermal regime favours the presence of permafrost. ERT shows the lowest resistivity values in the lower part of the alluvial fan and a highly resistivity zone in the upper sector of the fan and in the debris cones. These large variations in resistivity mark the presence of a saline water wedge from the sea into the fan, reaching frozen ground conditions about 100. m inland. It can be shown that the volcano-hydrothermal activity only inhibits frost development very locally, with frozen ground conditions occurring about 100. m away. Fil: Goyanes, Gabriel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Vieira, G.. Universidade de Lisboa; Portugal Fil: Caselli, Alberto Tomás. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cardoso, M.. Universidade de Lisboa; Portugal Fil: Marmy, A.. University of Fribourg; Suiza Fil: Santos, F.. Universidade de Lisboa; Portugal Fil: Bernardo, I.. Universidade de Lisboa; Portugal Fil: Hauck, C.. University Of Fribourg; Suiza

Deception Island is the most active volcano in the South Shetland Islands and has been the scene of more than twenty identified eruptions over the past two centuries. In this contribution we present the first comprehensive long-term volcanic hazard assessment for this volcanic island. The research is based on the use of probabilistic methods and statistical techniques to estimate volcanic susceptibility, eruption recurrence and the most likely future eruptive scenarios. We perform a statistical analysis of the time series of past eruptions and the spatial extent of their products, including lava flows, fallout, pyroclastic density currents and lahars. The Bayesian event tree statistical method HASSET is applied to calculate eruption recurrence, while the QVAST tool is used in an analysis of past activity to calculate the possibility that new vents will open (volcanic susceptibility). On the basis of these calculations, we identify a number of significant scenarios using the GIS-based VORIS 2.0.1 and LAHARZ software and evaluate the potential extent of the main volcanic hazards to be expected on the island. This study represents a step forward in the evaluation of volcanic hazard on Deception Island and the results obtained are potentially useful for long-term emergency planning., This work was supported by the European Commission (FP7 Theme: ENV.2011.1.3.3-1; Grant 282759: VUELCO) and the MICINN grant CTM2011-13578-E. AG is grateful for her Juan de la Cierva Grant (JCI-2010-06092) and Ramón y Cajal contract (RYC-2012-11024).

The hummocky terrains of Deception Island (Antarctic Peninsula) are continuous surfaces with decimetre to metre wide and decimetre depth bumps located mainly in the lower section of sloping lapilli and scoria terrains. A detailed study site between Cerro Caliente and Crater Lake was selected for the detailed mapping of hummocky terrains and for modelling their spatial distribution according to controlling geographical factors. A model of the susceptibility of occurrence of the hummocky terrains was created using the information value method, together with five independent variables: elevation, slope, global summer radiation, total curvature and lithology. Success and prediction rate curves were used for model validation and the Area Under the Curve index was used to quantify the levels of performance and prediction. The results were of high quality with a success rate of 88% and a prediction rate of 78%. The classes of the independent variables with more relevance in the occurrence of hummocky terrains were: elevation between 20–30 m and 60–70 m; concave or rectilinear/flat areas; slopes between 8 and 12o; tuff cones and maar deposits and global summer radiation between 1.8 and 2.0 TJm− 2. The good quality of the modelling results supports its use for assessing the future potential for formation of new hummocky terrain areas, or even to estimate the spatial distribution of buried ice within the permafrost environment of Deception Island.

13 pages, 8 figures, 1 table., [EN] Palaeostress results derived from brittle mesoscopic structures on Deception Island (Bransfield Trough, Western Antarctica) show a recent stress field characterized by an extensional regime, with local compressional stress states. The maximum horizontal stress (σy) shows NW–SE and NNE–SSW to NE–SW orientations and horizontal extension (σ3) in NE–SW and WNW–ESE to NW–SE directions. Alignments of mesofractures show a maximum of NNE–SSW orientation and several relative maxima striking N030-050E, N060-080E, N110-120E, and N160-170E. Subaerial and submarine macrofaults of Deception Island show six main systems controlling the morphology of the island: N–S, NNE–SSW, NE–SW, ENE–WSW to E–W, WNW–ESE, and NNW–SSE. Geochemical patterns related to submarine hydrothermally influenced fault and fissure pathways also share the same trends. The orientation of these fault systems is compared to Riedel shear fractures. Following this model, we propose two evolutionary stages from geometrical relationships between the location and orientation of joints and faults. These stages imply a counter-clockwise rotation of Deception Island, which may be linked to a regional left-lateral strike-slip. In addition, the simple shear zone could be a response to oblique convergence between the Antarctic and Pacific plates. This stress direction is consistent with the present-day movements between the Antarctic, Scotia, and Pacific plates. Nevertheless, present basalt-andesitic volcanism and deep earthquake focal mechanisms may indicate rollback of the former Phoenix subducted slab, which is presently amalgamated with the Pacific plate. We postulate that both mechanisms could occur simultaneously., [ES] El campo de esfuerzos actual obtenido a partir del análisis de mesoestructuras frágiles en la Isla Decepción (Cuenca de Bransfield, Antártida Occidental) esta caracterizado por un régimen distensivo con estados compresivos locales. La orientación del esfuerzo máximo en la horizontal (σy) es NO-SE y NNE–SSW a NE-SO y la dirección de extensión (σy) en la horizontal es ONO-ESE a NO-SE. El análisis en la orientación de las mesofracturas presenta un máximo absoluto en NNE-SSO y varios máximos relativos de dirección N030-050E, N060-080E, N110-120E y N160-170E. Por otro lado, las direcciones de fracturación a escala macroestructural, tanto en la zona emergida como sumergida, presenta seis direcciones principales de fracturación que controlan los rasgos morfológicos de la isla: N–S, NNE-SSO, NE-SO, ENE-OSO a E-O, ONO-ESE y NNO-SSE. Además, estas orientaciones coinciden con la distribución de las tierras raras relacionadas con los fenómenos de hidrotermalismo en Port Foster, así como con la localización de los fenómenos hidrotermales, magmáticos y sísmicos recientes. La orientación y distribución de los sistemas de fracturas es equivalente a las estructuras secundarias de las zonas de cizalla semifrágil o fracturas de cizalla de Riedel. Tomando como base este modelo, es posible distinguir dos estados evolutivos que implican una rotación sinistrórsum de la Isla Decepción asociada a una zona de cizalla simple generada por la convergencia oblicua entre las placas Antártica y Pacifica. La dirección de esfuerzos determinada a partir del análisis poblacional de fallas, así como la distribución y orientación de la fracturación observada en la Isla Decepción son coherentes con los movimientos de desagarre que caracterizan la dinámica actual de las placas Antártica, de Scotia y Pacífica. Sin embargo, los rasgos geoquímicos del vulcanismo (basáltico-andesítico) y profundidad de los hipocentros sugieren que ambos están asociados a un procesos de hundimiento pasivo de la Placa Phoenix (actualmente soldada a la Placa Pacifica). En este trabajo se propone que ambos procesos (movimientos de desgarre y hundimiento pasivo de la Placa Pacifica bajo la Placa Antártica) actuarían conjuntamente., Financial support for this research was provided by the projects ANT98-1557-E/HESP and REN2001-0643 of the Spanish Antarctic Program.