Major Collapse Research Articles

Automatic Monitoring of Rock‐Slope Failures Using Distributed Acoustic Sensing and Semi‐Supervised Learning

AbstractEffective use of the wealth of information provided by Distributed Acoustic Sensing (DAS) for mass movement monitoring remains a challenge. We propose a semi‐supervised neural network tailored to screen DAS data related to a series of rock collapses leading to a major failure of approximately 1.2 million on 15 June 2023 in Brienz, Eastern Switzerland. Besides DAS, the dataset from 16 May to 30 June 2023 includes Doppler radar data for partially ground‐truth labeling. The proposed algorithm is capable of distinguishing between rock‐slope failures and background noise, including road and train traffic, with a detection precision of over . It identifies hundreds of precursory failures and shows sustained detection hours before and during the major collapse. Event size and signal‐to‐noise ratio (SNR) are the key performance dependencies. As a critical part of our algorithm operates unsupervised, we suggest that it is suitable for general monitoring of natural hazards.

Adapting to climate change: snow load assessment of snow galleries on the Iron Ore Line in Northern Sweden

The snow galleries along the Iron Ore railway line in northern Sweden have faced problems in recent years due to increasingly large snow loads, and several galleries have been damaged. These incidents motivated an evaluation of the maximum load supported by the galleries before collapse, which is presented in this study. In 2021, a monitoring system was installed in one of the main frames of two snow galleries built in the 1950s to follow up with temperature and displacements, including a trigger that sends out a warning message when a critical load is reached. A literature review on snow loads was performed, followed by calculations on snow distribution on the galleries based on the Eurocodes and National Swedish Standards. Finite element 2D and 3D models were created using AxisVM to accurately assess the efforts in the structural elements. Analysis and discussion are complemented by observations from site visits. It was concluded that the critical loads supported by the galleries are lower than the requirements of today’s standards, but since secondary construction elements were damaged before the main frames reached their full capacity, no major collapse has yet taken place. The cobweb effect (load re-distribution between the neighboring elements in a 3D structure) influenced the behavior of the galleries in the 3D analysis and the capacity of the main frames proved to be significantly increased compared to the 2D assessment.

Geological structure of karst stratigraphical windows at Škocjan Caves, Slovenia

Within the UNESCO Škocjan Caves, detailed geological structural mapping of the cave passages and of the surface above the cave revealed interesting structural-lithological characteristics of two major collapse dolines, Velika Dolina and Mala Dolina. As a result of the karst processes effects and the formation of collapse dolines, older—stratigraphically lower—carbonates of the Sežana Formation (K22−4) crop out at the surface, underlying rocks of the younger Lipica Formation (K24−5). Here we do not recognize karst windows only in a geomorphological sense but, acknowledging the characteristic lithostratigraphical relationships involved, we suggest use of the new expression “karst stratigraphical window”. Recognizing that karstic areas contain numerous collapse dolines and other doline types, we presume that many more examples of karst stratigraphical windows exist, and that these are distinct from tectonic windows. Our study showed the importance that during the making of detailed geological surface maps of karst areas, it is essential to examine features such as collapse dolines, which may be identified as karst stratigraphical windows. Therefore, providing additional geological data, information about the stratigraphic boundaries and geological structure, in areas without abundance of outcropping rocks is resulting in a more inclusive and comprehensive geological maps.

Human-induced reactivation of a dormant earthflow? A geomorphological interpretation of historical mining maps of the Ischl salt mine (Austria)

This case study from the Northern Calcareous Alps demonstrates the utilization of historical mining documents for geomorphological purposes, especially for landslide event documentation. A combination of geomorphological mapping and interpretation of up to 200 year old mining maps for the Ischl salt mine (Austria) revealed the existence of a 500 m-long earthflow in an area where the engineering geology has been well investigated. The CAD-based creation of a polythematic map (surface and subsurface features) led to the conclusion that a prehistoric earthflow has been partly reactivated between 1850 and 1934 due to mining subsidence. The depletion zone of the historical earthflow is situated directly above the major collapse zone of the mine. Reactivation was most likely to have been caused by the lowering of the slope base due to the slow development of a subsidence trough within the ductile Haselgebirge Formation. Particularly for engineering geomorphological tasks in post-mining-areas, where subsurface facilities are no longer accessible, a combined approach of historical mining map analysis and geomorphological mapping can be regarded as a promising and cost-effective working concept. Supplementary material : Historical ground plans and cross-sections listed in Table 1 are available at https://doi.org/10.6084/m9.figshare.21740459 Thematic collection: This article is part of the Engineering Geology and Hydrogeology of the Anthropocene collection available at: https://www.lyellcollection.org/topic/collections/engineering-geology-and-hydrogeology-of-the-anthropocene

Cryptocurrency Risks, Fraud Cases, and Financial Performance

In this study, we examine major cryptocurrencies, present notable fraud cases, describe fraud risks, and analyze cryptocurrency financial performance. People debate whether cryptocurrency is an investment opportunity, the new Dutch Tulip Bubble, or a giant Ponzi scheme. There have been a number of high-profile fraud cases associated with cryptocurrencies, such as the FTX scandal in late 2022, thereby making fraud a real concern to current and potential future investors. Regarding financial performance, cryptocurrencies experienced a major collapse in value in the most recent period of the study, about three times worse than the major stock market indices. While in prior periods, cryptocurrencies have significantly outperformed stock market indices, recent fraud cases and the extreme volatility of cryptocurrencies indicate that investing in cryptocurrencies comes with much higher risk than traditional stock market investments. The debate over the investment potential of cryptocurrencies continues, whether they have long term value or are simply the new Dutch Tulip Bubble. The study’s findings will be useful to investors, regulators, and academic researchers regarding the cryptocurrency industry.

Coral reef resilience persisted for a millennium but has declined rapidly in recent decades

The lack of long-term records of coral community composition restricts our understanding of the contemporary ecological states of tropical reefs. Here we integrated paleo-ecological reconstruction, historical mortality evidence, and ecological survey data to determine the temporal variability in reef resilience of the Nansha atolls in the tropical western Pacific. Subfossil coral assemblages extracted from the reef cores exhibited no evidence of community shifts attributable to centennial-scale changes in El Niño variability during the last millennium, suggesting long-term stability in community structure and persistence of reef resilience. By contrast, ecological surveys revealed a major collapse in the reef ecosystem, and high-precision U-series dating of deadAcroporafragments indicated that this collapse occurred in recent decades and was especially relevant to several strong/extreme El Niño episodes. Frequent and intensive El Niño−Southern Oscillation and marine heatwaves have overwhelmed the reefs’ resistive and recovery capacity, thereby impairing reef resilience.

Seismic Analysis of Historical Urban Walls: Application to the Volterra Case Study

Several Italian cities are characterized by the presence of centuries-old historic walls, which have a cultural heritage value and, due to their structural role as a retaining wall, often influence the safety of adjacent buildings and infrastructure. Ancient urban walls are increasingly subject to instability and collapse phenomena, because the greater frequency of extreme meteoric events aggravates the static condition of the walls and of the wall–soil system. Since the seismic risk in the contexts in which the historical urban walls are located is often medium-high, it is advisable to evaluate the influence of soil moisture on the seismic response of the soil–structure system. In this paper, the seismic vulnerability of historical urban walls was examined through considering scenarios of both dry and wet soil, in order to evaluate the seismic response of the structure as a function of soil imbibition. Seismic vulnerability analyses were carried out on the case study of the historical urban masonry walls of Volterra (Italy), which have been affected by two major collapses in the last ten years. Seismic vulnerability was assessed by means of the limit equilibrium method and the finite element method, and through adopting proper soil imbibition models. The results highlight which sections of the walls are at greater seismic risk due to the presence of soil moisture, as well as the influence of soil imbibition on the structural safety and failure mechanism.

Analysis on the Development Status of China’s Overseas Purchasing Market during the Epidemic

Since the beginning of the COVID-19, many areas have been locked down. It means that you cannot go abroad to play or buy, but as time gradually increases, the stop of tourism means that everyone can only stay in their own country. Buying has also become a big problem. How to buy these products through the Internet? Overseas purchasing is the way that the purchasing agent help the customers buy the items that customers need and transport and collect the most suitable courier company for the customers. There will be international mailing in different regions, but not everyone will accept the cost of international mailing. To have the interests of both parties, it is necessary to find a more suitable shipping price. Transportation is also divided into different types, there are many different modes of transportation by air or sea. However, due to the epidemic, to allow everyone to get their packages more safely, all transportation will take about half a month to a month. Purchasing is not a job that can be done by one person, because he is not just buying. When the number of customers gradually increases, it is impossible for one person to complete everything. This paper mainly discusses the development status of China’s overseas purchasing market during the epidemic. The study shows that due to the epidemic, many purchasing agent cannot fly freely to buy items, which leads to a major collapse of the purchasing agent market.

Sensitivity of phytoplankton, zooplankton and macroinvertebrates to hydrogen peroxide treatments of cyanobacterial blooms

Addition of hydrogen peroxide (H2O2) is a promising method to acutely suppress cyanobacterial blooms in lakes. However, a reliable H2O2 risk assessment to identify potential effects on non-target species is currently hampered by a lack of appropriate ecotoxicity data. The aim of the present study was therefore to quantify the responses of a wide diversity of freshwater phytoplankton, zooplankton and macroinvertebrates to H2O2 treatments of cyanobacterial blooms. To this end, we applied a multifaceted approach. First, we investigated the 24-h toxicity of H2O2 to three cyanobacteria (Planktothrix agardhii, Microcystis aeruginosa, Anabaena sp.) and 23 non-target species (six green algae, eight zooplankton and nine macroinvertebrate taxa), using EC50 values based on photosynthetic yield for phytoplankton and LC50 values based on mortality for the other organisms. The most sensitive species included all three cyanobacterial taxa, but also the rotifer Brachionus calyciflores and the cladocerans Ceriodaphnia dubia and Daphnia pulex. Next, the EC50 and LC50 values obtained from the laboratory toxicity tests were used to construct a species sensitivity distribution (SSD) for H2O2. Finally, the species predicted to be at risk by the SSD were compared with the responses of phytoplankton, zooplankton and macroinvertebrates to two whole-lake treatments with H2O2. The predictions of the laboratory-based SSD matched well with the responses of the different taxa to H2O2 in the lake. The first lake treatment, with a relatively low H2O2 concentration and short residence time, successfully suppressed cyanobacteria without major effects on non-target species. The second lake treatment had a higher H2O2 concentration with a longer residence time, which resulted in partial suppression of cyanobacteria, but also in a major collapse of rotifers and decreased abundance of small cladocerans. Our results thus revealed a trade-off between the successful suppression of cyanobacteria at the expense of adverse effects on part of the zooplankton community. This delicate balance strongly depends on the applied H2O2 dosage and may affect the decision whether to treat a lake or not.

Refocusing SIDS research: Is butylcholinesterase a predictive biomarker?

Unexpected infant and childhood deaths are defined as those where the child was not thought by the family or healthcare professionals to be at risk of death 24 hours before the death or the major collapse leading to the death.1 Unexpected deaths include those subsequently shown to be explained by rapidly progressive natural causes e.g., previously unrecognised cardiac abnormalities, or infections, accidental and non-accidental trauma, drowning and suicide. They also include sudden infant death syndrome a term allocated to an infant death (< 1 year) when no sufficient explanation can be identified following a thorough investigation of the scene and circumstances of death, a post-mortem examination including microbiology and histopathology performed by a pathologist or medical examiner with paediatric training, and a multi-professional review of all available information.

Genesis Analysis of Ground Collapse in Wuhan Based on 3D Geological Model

Ground collapse has been one of the main types of geological disasters in Wuhan City. It can be characterized by complex disaster-inducing environment, diverse disaster-causing factors, fragile disaster-bearing bodies, and serious consequences. In this study, a 3D geological structure model of the area was established by collecting data from major ground collapse incidents in Wuhan that have occurred over the years and by combining them with geological data obtained from boreholes. The model was used to analyze the distribution of ground subsidence in the city and reveal the geological causes of ground subsidence accidents in this area. The results showed that ground collapse is mainly distributed in the karst development area along the Yangtze River in Baishazhou. The karst was most developed at the intersection between the Yangtze River fault and the Hanyang fold belt. The ground collapse incidents showed two main characteristics in terms of their spatial distribution. Most of the collapse areas developed in the central third limestone belt. Most of the collapses are located on the first terrace of the Yangtze River. Most collapse points were controlled by geomorphic units (first terrace), stratigraphic age (Holocene) and stratigraphic combination (a binary structure composed of clay as the upper part and fine sand as the lower part, and the bottom is a gravel layer, containing pore confined water). The karst collapse in Fenghuo Village was selected as a case study to analyze the evolution process and disaster-causing mechanism of the karst collapse. Groundwater extraction was found to be the main reason for the karst collapse. The research results provide a geological basis for the planning layout and urban construction in Wuhan City.

Revealing the Morphological Evolution of Krakatau Volcano by Integrating SAR and Optical Remote Sensing Images

On 22 December 2018, volcano Anak Krakatau, located in Indonesia, erupted and experienced a major lateral collapse. The triggered tsunami killed at least 437 people by the 13-m-high tide. Traditional optical imagery plays a great role in monitoring volcanic activities, but it is susceptible to cloud and fog interference and has low temporal resolution. Synthetic aperture radar (SAR) imagery can monitor volcanic activities at a high temporal resolution, and it is immune to the influence of clouds. In this paper, we propose an automatic method to accurately extract the volcano boundary from SAR images by combining multi-polarized water enhancement and the Nobuyuki Otsu (OTSU) method. We extract the area change of the volcano in 2018–2019 from Sentinel-1 images and ALOS-2 imagesThe area change and evolution are verified and analyzed by combing the results from SAR and optical data. The results show that the southeastern part of the volcano expanded significantly after the eruption, and the western part experienced collapse and recovery. The volcano morphology change experienced a slow-fast-slow process in the two years.

Influence of low-Z impurity on the stabilization of m/n = 2/1 tearing/locked modes in EAST

The impact of the low-Z impurity concentration on mode stabilization has been investigated in the EAST tokamak. A series of tearing modes (TMs) with multiple helicities are excited by the low-Z (carbon) impurity concentration, and the dominant mode structure features m/n = 2/1 magnetic islands that propagate in the electron diamagnetic drift direction (m and n are poloidal and toroidal mode numbers, respectively). The m/n = 2/1 locked modes (LMs) can be formed by the redistribution of low-Z impurity concentration, and are unlocked spontaneously due to the decrease in the impurity concentration, where the width of the magnetic islands can reach w ≈ 5 cm (w/a ≈ 0.1, a is the minor radius). The increase in the electromagnetic brake torque is the primary reason for the mode locking, and the ‘O’-point of the m/n = 2/1 magnetic islands is locked by the tungsten protector limiter (toroidal position: −0.4π ⩽ ϕ ⩽ −0.3π) with separation of Δϕ ≈ 0. The 3D asymmetric structure of the m/n = 2/1 magnetic islands is formed for the interaction with the tungsten protector limiter, and the electromagnetic interaction decreases dramatically for the separation of Δϕ ⩾ 0.2π. The mode excitation and locking mechanisms can be illustrated by the ‘hysteresis effect’ between the low-Z impurity concentration and the width of the m/n = 2/1 magnetic islands; namely, the growth of magnetic islands is modulated by the low-Z impurity concentration, and the rotation velocity is decelerated accordingly. However, the intrinsic mechanism for the unlocking of m/n = 2/1 LMs is complicated by considering the concentration of the low-Z impurity, and the possible unlocking mechanism is discussed. Therefore, understanding the relationship between the impurities and magnetic islands is more important for optimization of the control techniques (resonant magnetic perturbations → LMs, electron cyclotron resonant heating (ECRH) → neoclassical tearing mode (NTM), impurity seeding → major collapse, etc).

Characteristics and Evolution of Tunnel Collapse in Fully-Weathered Coastal Red Sandstone Strata

Xu, H.; Shao, Z.; Chen, C.; Wang, Z.; Cai, L.; Li, Z., and Huang, C., 2022. Characteristics and evolution of tunnel collapse in fully-weathered coastal red sandstone strata. Journal of Coastal Research, 38(2), 289–301. Coconut Creek (Florida), ISSN 0749-0208. Understanding characteristics of tunnel collapse and its evolution is the premise of effective prevention and control. Fully-weathered coastal red sandstone is widely distributed in coastal areas, and the characteristics of tunnel collapse under this stratum are not clear. This paper studies characteristics of tunnel collapse and its evolution by conducting a model test of tunnel excavation in fully-weathered coastal red sandstone with digital image processing, where the whole process of rock mass failure, displacement, and strain variations are studied. The results show that: (1) the instability failure of the fully-weathered coastal red sandstone rock mass is a progressive process under the load. Three major collapses occur consecutively, where the first and the second start at the arch foot and arch waist, respectively; both manifested as cracks developing upward to the middle until the cracks penetrate. The third is mainly manifested as the collapse of rock mass block above the tunnel crown. (2) The displacement and shear strain around the tunnel increase first with the load and then stabilize. The vertical displacement is more significant than the horizontal displacement. Tunnel crown is where the vertical displacement increases the fastest and accumulates the most, which directly threatens the rock mass stability and thus deserves special attention. The arch waist has the most intense change of shear strain. (3) All three collapses end up forming a stable balanced arch. The three collapses show the evolution that the foot of the balanced arch gradually moves horizontally outward, and the height of the balanced arch gradually expands upward. The shape of the balanced arch can be well fitted by a parabolic function. Practical suggestions on tunnel collapse prevention and control of fully-weathered coastal red sandstone are also put forward.

Intracaldera explosions and lava emissions during the 2007 caldera collapse of Piton de la Fournaise, La R\xe9union Island

The March–April 2007 Piton de la Fournaise basaltic eruption was the most significant eruption on La Réunion Island in historical times. On 2 April, a fissure opened on the southeastern flank of the volcano. Vigorous fountains fed lavas that rapidly reached the coast. Three days later, on the 5–6 April, major caldera collapse occurred at the summit, affecting the floor and walls of Dolomieu caldera. Monitoring records, primarily webcam images, have been analysed and integrated with geophysical data to reconstruct the chronology of events at the summit during caldera collapse. Those events included progressive subsidence of the former caldera floor, landslides, explosions, lava emissions and steam fumaroles, and lasted until 19 April though diminished greatly in frequency after 7 April. For two days after the main caldera collapse on 5 April, subsidence increments, intracaldera lava emission and explosions were closely associated in time and in location. Abundant steam and wet talus on the caldera walls imply that the shallow hydrothermal system and/or groundwater were exposed by subsidence. The presence of juvenile components in ash deposited at the summit during caldera collapse and the close link between intracaldera lavas and explosions suggest that many explosions were phreatomagmatic. Although caldera collapse was related to magma withdrawal from beneath the summit via the flank vent activity, numerous intracaldera lava emissions indicated that magma was nevertheless present at the summit during caldera collapse. We infer that the lava emissions were fed by an intrusion emplaced at the end of March into the eastern summit region and that the intrusion was being actively recharged during caldera collapse. Caldera collapse involved a complex combination of magma withdrawal and magma replenishment at separate summit reservoirs.

Re-colonization of hostile environments by benthic foraminifera: an example from Montserrat, Lesser Antilles Volcanic Arc

The Soufrière Hills Volcano, on the island of Montserrat, has an eruption history spanning over 2 million years. During this time the volcano has undergone multiple eruptions with intervening periods of low activity or dormancy. The most recent activity began in 1995 and has seen a series of major eruptive events. One of the most recent of these, and the focus of this study, occurred on the 20th May 2006. This major dome collapse produced 90 million m3 of volcanic material in only 3 hours, propelling ash clouds through the air and pyroclastic flows down the side of the volcano and into the sea. In this study of benthic foraminifera, cores from four sites off-shore Montserrat are analysed, including those collected from a location within the path of the 2006 ash cloud, around 10 km west of the Montserrat coast. In this area, one core contained 6-7 cm of ash overlying hemipelagic sediments. Volcanic ash is present in two distinct layers, one 3 cm layer produced by the 2006 eruption and the other, 3-4 cm layer, from an earlier eruption in 2003. Other cores were collected from areas unaffected by recent ash fall deposits and provide a base line for comparisons within the affected areas. To the east and south-east of Montserrat there is a different situation as this is the direction of travel of massive pyroclastic flows down the Tar Valley and the impact on the sea floor is more dramatic. There are also two extinct volcanic centres that allow the investigation of sea floor re-colonization on different time scales. The sites to the west of Montserrat record rapid colonization by benthic foraminifera of opportunistic taxa, comparable to that seen near Mt Pinatubo in the South China Sea while the sites to the east record a slower pattern of re-colonization by a wider spectrum of taxa, similar to that recorded at Deception Island in the Southern Ocean, with different benthic taxa performing the pioneering role.

Crystal Mush Growth and Collapse on a Steep Wall: The Marginal Border Series of the Skaergaard Intrusion, East Greenland

Abstract The Skaergaard Intrusion of East Greenland solidified as a closed system, with the development of progressively more fractionated material at the roof, floor and vertical walls of the magma chamber. We argue, using field observations of the exposed western margin together with detailed microstructural and geochemical analysis, that the mush on the vertical walls of the Skaergaard Intrusion reached a maximum thickness of ~180 m, and was highly unstable. Material was lost both continuously, due to non-retention of poorly consolidated material, and during episodic collapse events. The almost complete absence in the wall rocks of material formed in LZc times (following the saturation of the bulk magma in Fe-Ti oxides) was likely to have been caused by a collapse event, perhaps related to faulting of the actively extending Greenlandic margin. A second major collapse of the MBS occurred during the later stages of solidification, with the greatest loss of material occurring in a region of the wall with an unusually thick mush, creating a transient and localised increase in the thickness of the floor mush. This work demonstrates the importance of vertical walls in supplying loose, disaggregated material to form mobile magmatic slurries that may contribute to floor cumulates or be entrained and erupted in long-lived systems.

Quantifying the potential future contribution to global mean sea level from the Filchner–Ronne basin, Antarctica

Abstract. The future of the Antarctic Ice Sheet in response to climate warming is one of the largest sources of uncertainty in estimates of future changes in global mean sea level (ΔGMSL). Mass loss is currently concentrated in regions of warm circumpolar deep water, but it is unclear how ice shelves currently surrounded by relatively cold ocean waters will respond to climatic changes in the future. Studies suggest that warm water could flush the Filchner–Ronne (FR) ice shelf cavity during the 21st century, but the inland ice sheet response to a drastic increase in ice shelf melt rates is poorly known. Here, we use an ice flow model and uncertainty quantification approach to project the GMSL contribution of the FR basin under RCP emissions scenarios, and we assess the forward propagation and proportional contribution of uncertainties in model parameters (related to ice dynamics and atmospheric/oceanic forcing) on these projections. Our probabilistic projections, derived from an extensive sample of the parameter space using a surrogate model, reveal that the FR basin is unlikely to contribute positively to sea level rise by the 23rd century. This is primarily due to the mitigating effect of increased accumulation with warming, which is capable of suppressing ice loss associated with ocean-driven increases in sub-shelf melt. Mass gain (negative ΔGMSL) from the FR basin increases with warming, but uncertainties in these projections also become larger. In the highest emission scenario RCP8.5, ΔGMSL is likely to range from −103 to 26 mm, and this large spread can be apportioned predominantly to uncertainties in parameters driving increases in precipitation (30 %) and sub-shelf melting (44 %). There is potential, within the bounds of our input parameter space, for major collapse and retreat of ice streams feeding the FR ice shelf, and a substantial positive contribution to GMSL (up to approx. 300 mm), but we consider such a scenario to be very unlikely. Adopting uncertainty quantification techniques in future studies will help to provide robust estimates of potential sea level rise and further identify target areas for constraining projections.

Distinctive patterns and signals at major environmental events and collapse zone boundaries

We studied the patterns of pre-collapse communities, the small-scale and the large-scale signals of collapses, and the environmental events before the collapses using four paleoecological and one modern data series. We applied and evaluated eight indicators in our analysis: the relative abundance of species, hierarchical cluster analysis, principal component analysis, total abundance, species richness, standard deviation (without a rolling window), first-order autoregression, and the relative abundance of the dominant species. We investigated the signals at the probable collapse triggering unusual environmental events and at the collapse zone boundaries, respectively. We also distinguished between pulse and step environmental events to see what signals the indicators give at these two different types of events. Our results show that first-order autoregression is not a good environmental event indicator, but it can forecast or indicate the collapse zones in climate change. The rest of the indicators are more sensitive to the pulse events than to the step events. Step events during climate change might have an essential role in initiating collapses. These events probably push the communities with low resilience beyond a critical threshold, so it is crucial to detect them. Before collapses, the total abundance and the species richness increase, the relative abundance of the species decreases. The hierarchical cluster analysis and the relative abundance of species together designate the collapse zone boundaries. We suggest that small-scale signals should be involved in analyses because they are often earlier than large-scale signals.

Geology and conceptual model of the Domuyo geothermal area, northern Patagonia, Argentina

The western slope of Cerro Domuyo in northern Patagonia is characterized by thermal springs with boiling waters, Quaternary silicic domes, and pyroclastic deposits that suggest the existence of a geothermal reservoir. According to geochemical studies, the reservoir may have a temperature of 220°C and one of the largest advective heat fluxes reported for a continental volcanic center. In this paper, we propose a more refined conceptual model for the Domuyo geothermal area, based on a geological survey supported by UPb, UTh, and ArAr geochronology and by magnetotelluric and gravity surveys. Our study indicates that the Domuyo Volcanic Complex (DVC) is a Middle Pleistocene dome complex overlying middle Miocene to Pliocene volcanic sequences, which in turn cover: 1) the Jurassic-Early Cretaceous Neuquén marine sedimentary succession, 2) silicic ignimbrites dated at ~186.7Ma, and 3) the Paleozoic metamorphic basement intruded by ~288Ma granite bodies. The volcanic cycle in the DVC is distinctly bimodal, characterized by the emplacement of massive silicic domes and less voluminous olivine basalts on its southern slope. A major collapse of the central dome at ~600ka produced a voluminous (19.4km3 and 133km2) block-and-ash flow, and associated pyroclastic flows, that filled a valley to the southwest at distances up to ~30km from Cerro Domuyo summit. This was followed by a period of intense effusive activity that formed the Cerro Guitarra, Cerro Las Pampas, Cerro Domo, and Cerro Covunco silicic domes. The last two domes are the youngest and largest edifices, dated at 0.50Ma (ArAr age) and 0.25Ma (UTh age). Pre-Cenozoic successions were affected by N-S reverse and thrust faults that were later displaced by an ENE-WSW-trending transtensional belt. The basement rocks at the northern termination of the Cordillera del Viento anticlinorium were also displaced towards the east-northeast by this belt, which is observed NNW of Cerro Domuyo. The DVC was emplaced within this zone of crustal weakness. The integration of geologic observations with magnetotelluric and gravity data, allowed us to develop an updated conceptual model of the geothermal system. The geothermal reservoir is inferred at a depth of less than 2km within pre-Pliocene fractured rocks, bounded by ~WSW-ENE trending faults and sealed by the pyroclastic deposits and rhyolitic lavas of the DVC. The location of most thermal springs is not directly controlled by faults. Instead, flows emerge at the contact between the fractured and faulted basement and the caprock.