ABSTRACT Aim To gain detailed insights into how vertebrate intraspecific diversity can be generated and maintained within volcanic islands, using genomic data. Location The Canary Islands of Tenerife and La Palma. Time Period Tissue samples were obtained in 2003. Genomic analyses were performed in 2023–25. Taxon The endemic gecko, Tarentola delalandii . Methods Genotyping‐by‐sequencing of DNA from 109 Tarentola delalandii from the islands of Tenerife (31 sites) and La Palma. SNPs and sequence tags were analysed to identify genomic groups from ancestry coefficients. Bayesian multicoalescent and other phylogenetic approaches allowed determination of relationships among individuals and groups, times of divergence and secondary contact. Levels of admixture were evaluated using hybrid indices, multicoalescent approaches and ancestry coefficients. Results Six genomic clusters were detected within Tenerife (plus one from La Palma). Within‐island population divergence events beginning some 1.3–2.7 Ma ago explain diversification. Divergence time estimates were more recent than previous mtDNA‐based estimates but aligned closely with estimates for other Tenerife species. Population fragmentation on the east coast appears to have been mediated by the Güímar valley mega‐landslide some 0.8 Ma ago. Despite strong spatial associations, divergence of lineages to the NW (Teno) and NE (Anaga) of the Teide stratovolcano post‐dated the appearance of respective Miocene and Pliocene shield volcanoes. Instead, these long‐term geologically stable regions likely provided refugia during eruptions on the central shield. Multiple secondary contact of divergent populations likely occurred in the late Pleistocene. Limited introgression across contact zones has potentially maintained ancient genomic structuring. La Palma was colonized 0.3–0.8 Ma ago from a Tenerife north coast lineage. Main Conclusions We outline how present‐day spatial genomic structuring might be created and maintained within a small island. Mega‐landslides and volcanic eruptions initially fragmented populations during the Pleistocene while limited introgression following secondary contact has maintained stable associations of lineages with geographical areas.

ABSTRACT Understanding geological structures, which primarily control groundwater distribution, potential, and flow systems, is essential for sustainable groundwater management. The objective of this study is to investigate the influence of geological structures within volcanic rock units on the region's groundwater potential and borehole and spring yields, providing practical and relevant insights. Furthermore, this study identifies the structural controls that impact the groundwater potential and distribution in the study region. Various methodological approaches, including data collection through intensive fieldwork, evaluation of previous works, satellite image interpretation, and an inventory of groundwater sources (boreholes and springs) from regulatory datasets, were employed to achieve the study's objective. Borehole (23) and spring (22) data collection for validation, along with a detailed assessment of published and previously unpublished works, contribute to the study region's condensed results and interpretations. The analysis results show that structural dynamics have been passed through persistent tectonics and deformation. Those imprints can be found in the study region, thus determining groundwater occurrence and flow. From the 22 boreholes reported in the study region, nine boreholes (40%) were abandoned, mainly in the western part of the Blue Nile River (8 boreholes) and one borehole in the Zenzelma area. The springs primarily concentrate on lithologic contacts and along the fault lines in the southern section of the study area. Among the productive wells (60%), a significant variation in well yield is observed, ranging from 2.5 L/s to 60 L/s, making the controlling factor very complex. The primary geological structures that govern groundwater flow systems are the deep‐seated NE–SW, NW‐SE, and N‐S faults, the N‐S‐trending radial dike, the NE–SW‐trending radial fracture, and the NW‐SW chain of cinder cones. The upper section of the Andasa area (Adiet‐Gonj Kolela), characterised by a thick, structurally undeformed, massive base of a shield volcano, is unfavourable for groundwater occurrence and flow. Topographically high and less deformed crystalline volcanic rocks make the area unsuitable for groundwater exploration and exploitation. The eastern part of the Andasa (Abune‐Hara area) and the western part of the Andasa watershed are characterised by NE–SW radial fractures and faults, which cause springs to discharge at the points of convergence of these fractures. Moreover, structural analysis and the nature of tectonic evolution within the study area suggest a strong possibility of an N‐S trending buried dike and a multidirectional radial/feeder dike extending towards Lake Tana and the centre of the cone conduit, respectively. The collapsed surface is a potential site for groundwater occurrence. However, deep N‐S faults aligned with the Blue Nile River require careful consideration. The implications of NW‐SE‐oriented cones and buried dikes, overlaid with Quaternary basalt and sediments, mislead groundwater experts. Generally, this work clustered the set of geological structures that control groundwater flow and occurrence. Despite the need for a detailed analysis of the effects of the feeder dike, scoria cone chain, and the N‐S aligned section of Upper Blue Nile River, the highly fractured zone east and west of the Andasa plain, the lower area of the Andasa plain, and the Meshenti region (west) represent a groundwater potential zone. This study is novel in identifying, clustering, and characterising the complex cross‐cutting relationships among geological structures formed by multiple deformations in the study region to determine groundwater occurrence and barrier zones for future exploration and extraction.

Based on the concept of presenting exceptional and extraordinary sites for protection or preservation for humanity, the current research proposes two different Ecuadorian caves as exceptional candidates for the World Heritage List of the UNESCO. The first cave named Tayos, is a typical 5 km long, karstic cave situated in the Amazonian lowland, being composed predominantly of chemical and clastic sediments of Triassic age. The cave exhibits clear signs of structural fragmentation and some folding. The second cave, named Triple Volcano, is a volcanic cave in form of volcanic conduct, situated in the outer part of the Sierra Negra shield volcano, at Isabela Island in the Galapagos. So far, its the deepest mapped structure of the entire Galapagos archipelago. This cave represents an exceptional nice preserved multi-colored magma chamber of a parasitic volcanic cone, which has been situated very close to the surface. Both caves are remote of human settlings and of difficult, vertical access. The research has been based on an intensive inventory of existing speleological literature of Ecuador in all types of aspects, including mapping, culture, geology, flora and fauna as well as documents based on many books and filmography, besides various own expeditions. The high amount of existing material, specially of the tayos cave, has been earned on the worldwide interest based on a variety of legends mianly due to the unusual inner landscape. In popular culture, these myths revolve around the arrival and existence of extraterrestrials and intraterrestrials, the supposed discovery of metal plates or books and various other treasures, such as golden statues, hieroglyphs and prehistoric antiquities unknown to mankind. The two studied caves are presented and described in detail. Both geosites, Triple Volcano as well as Tayos cave are recognized to be extraordinary candidates for the World Heritage List, as they accomplish various of the given ten criterias of the UNESCO, for their potential inclusion. Both caves contribute positively to the World Natural Heritage designation as examples of unique scenic beauty, scientific and cultural values as well as they constitute global hotspots of underground bio- and geodiversity.

Abstract Pu‘u‘ō‘ō is Kīlauea’s longest lived (1983–2018) and most voluminous (~4.4 km3) historical eruption. New oxygen isotope data are presented for matrix material from lava erupted from 2006 to 2018, olivine from 1997 to 2018, clinopyroxene from 2013 to 2018 (first such data for Kīlauea), and matrix from two 1982 summit eruptions. These data are integrated with our previously published oxygen isotope results for the first part (1983–1997) of the Pu‘u‘ō‘ō eruption and 19–20th century Kīlauea summit eruptions and compared with published whole-rock XRF and Sr isotope data. This study builds on our previous work (using whole-rock and mineral chemistry) that indicated strong evidence for mixing of evolved magmas, which had undergone shallow storage, crystal fractionation, and crustal contamination, with new, mantle-derived magma. Pu‘u‘ō‘ō δ18O values range from 4.4 to 4.9‰ for olivine and 4.6–5.7‰ for matrix. Both are ~0.1–0.9‰ lower than the canonical mantle δ18O value. Olivine δ18O values are relatively constant during the eruption (4.7 ± 0.1‰), whereas matrix δ18O values progressively increased reflecting the flushing of contaminated magma from the feeder system. The δ18O results from Pu‘u‘ō‘ō and other Kīlauea historical lava provide evidence of ~200 years of recurring crustal contamination within the volcano. Equilibrium in O isotopes between the matrix and coexisting olivine was periodically established after major changes in the Pu‘u‘ō‘ō eruption and for summit eruptions. New, mantle-derived magma was contaminated in the summit reservoir after several major collapses (100+ m) and eruptive hiatuses, and in the east rift zone as magma was stored for weeks to decades. Poor correlations (R2 ≤ 0.1) were found between olivine and matrix δ18O values with Nb/Y and Sr isotopes for Pu‘u‘ō‘ō and historical Kīlauea summit lavas (1820–1982) exhibiting O isotope equilibrium. Thus, the ranges in olivine and matrix δ18O values in Kīlauea’s historical lava are not indicative of δ18O heterogeneity in its mantle source. Kīlauea’s mantle source has an apparently narrow range of δ18O values (5.6 ± 0.1‰) as evidenced by matrix O isotope values for its more primitive summit lavas and those from the latter part of the Pu‘u‘ō‘ō eruption. Olivine from young Hawaiian shield volcanoes with KEA-like (Kīlauea and Mauna Kea) and LOA-like (Kama’ehuakanaloa and Mauna Loa) sources have nearly identical δ18O values (5.0–5.1) suggesting the Hawaiian plume source is essentially homogeneous in δ18O during shield stage for recent volcanism.

Abstract The observation of low viscosity lava flows and shield volcanoes on radar images, combined with X‐ray fluorescence analyses performed by Soviet landers, strongly suggests that Venus's crust is primarily basaltic. However, near‐infrared emissivity data from the Galileo and Venus Express missions indicate that crustal plateaus may be compositionally distinct and contain higher proportions of felsic minerals than the surrounding plains. The hypothesis that these highlands are felsic has led to suggestions of past oceans on Venus, as the generation of such rocks on Earth typically requires significant amounts of water. We use thermodynamic modeling to explore the conditions under which silica‐rich melts can form without water, through deep melting of basaltic crust in thickened crustal roots or during crustal recycling in the mantle. Felsic melts containing 60–65 wt.% can form at depths 60 km. In regions of thickened crust, such melts would be produced along a thermal gradient of 10 K/km, whereas for higher gradients (15 K/km), melting occurs at depths where quartz is not yet present (50 km), resulting in silica‐poor melts. The presence of small amounts of water allows similar felsic melts (in composition and volume) to form at moderately shallower depths (40 km). Our results indicate that large volumes of felsic melt could form even under anhydrous conditions on Venus, via crustal thickening or recycling mechanisms such as subduction or lithospheric dripping. This supports the idea that part of Venus's highlands could be the product of remelted basaltic crust, regardless of whether surface water existed in the past.

Abstract Lava tubes are subsurface conduits within a lava flow that feed its advance. Lava tube detection is important to understand lava flow dynamics and to mitigate geohazards. Here we use InSAR‐derived surface motion data, in combination with shortwave and thermal infrared imagery, to delineate a ∼14 km long lava tube system at Fernandina volcano, Galápagos, in 2024. The lava tubes developed during a 68‐day long eruption of basaltic lava. Individual branches of the lava tube system were mapped through a combination of: (a) spatio‐temporally stable, point‐like thermal anomalies (“skylights”) in syn‐eruption multispectral imagery; and (b) opposed, subsidence‐related, horizontal displacements defined by post‐eruption InSAR timeseries analysis. Recently elongated perpendicular baselines of the Sentinel‐1A satellite enabled estimation by InSAR of lava‐flow thickness and a lava‐field bulk volume of ∼84 ± 40 × 10 6 m 3 . Open‐channel flow transitioned to enclosed tube flow within the first 2 weeks of the eruption, once initial eruption rates of ∼7.5 × 10 6 m 3 DRE of magma per day (87 m 3 s −1 ) declined rapidly and non‐linearly to below ∼0.5 × 10 6 m 3 per day (6 m 3 s −1 ). The tube‐flow phase accounted for only 18% of the total erupted volume, but it facilitated 35% (5 km) of the total lava run‐out. Consistent with traditional field‐based observations, the remote sensing data sets illustrate the thermal efficiency of lava tube transport and its key role in the construction of shield volcanoes. Our findings also highlight the potential for multi‐sensor remote sensing approaches to inform future modeling of lava tube systems and lava flow run‐out.

Abstract. This study investigates the magma plumbing system of the Miocene volcano shield stage of Tenerife (Canary Islands) through a geothermobarometric analysis of clinopyroxenes in ankaramite dykes and lavas from the Teno and Roque del Conde massifs. Ankaramites, characterized by a high phenocryst content of olivine and clinopyroxene, provide valuable insights into magma storage and transport processes. Two different methods have been applied to estimate the pressure and temperature of crystallization of clinopyroxenes: (i) a novel machine learning geothermobarometer and (ii) a geobarometer that uses their structural parameters (Vcell and VM1 polyhedron). The results yielded a pressure distribution between 0 and 8 kbar with a difference between clinopyroxene cores and rims, reflecting a multi-level plumbing system with evidence for the progressive ascent and crystallization of magmas. Further considerations of aluminium incorporation into the tetrahedral site and zonation patterns of clinopyroxene cores revealed three groups with distinct P–T paths, which are Low-T, High-T, and Low-P clinopyroxenes. Low-T clinopyroxenes are the largest ones (up to few centimetres in size) and exhibit resorbed and patchy zonation. This group represents a relatively cold crystal mush formed from a more hydrated magma, accumulated during a long residence time in disequilibrium conditions, as testified by crystal habits. High-T clinopyroxenes show normal zonation pattern and consist of small crystals (1–2 mm in size) directly crystallized from a less hydrated carrier magma during its ascent from depth (> 20 km b.s.l.). This magma, which tore away part of the crystal mush bodies, acted as the transport agent of these two suites of crystals up to the shallower crustal reservoirs (0–7 km). At these depths, clinopyroxene cores of the Low-P group crystallized in the same P–T conditions as those of the rim domain, in a chemical disequilibrium regime, proved by resorbed and patchy textures. In this scenario, ankaramites witness the occurrence of a heterogeneous cargo of clinopyroxenes that formed at different depths in the plumbing system of the Teno and Roque del Conde massifs during the volcano shield stage. The results of our research extend previous geothermobarometric studies and refine the understanding of the ankaramite plumbing system of Tenerife. Our data are consistent with the plumbing systems of other shield volcanoes of the Canary Islands and Hawaii and boost the application of machine learning approaches in revealing the anatomy of volcano plumbing systems.

The Bight Basin, located on the passive margin of the Great Australian Bight, contains a complex network of post-breakup Paleogene-age igneous systems that formed following breakup from Antarctica in the Late Cretaceous. These systems include extensive mafic sheet intrusions (sills and laccoliths) that primarily occur within the Hammerhead Supersequence (Late Santonian–Maastrichtian) and extrusive features including shield volcanoes and lava flow fields (roughly mid-Eocene). Previous studies have primarily focused on describing the morphologies and emplacement of the intrusive bodies. However, questions remain about how extensive normal faulting within the Hammerhead Supersequence has affected the distribution of volcanic activity. Our study combines seismic interpretation of fault segments, eruptive centres and intrusions from multiple 3D seismic surveys to explore how structural and geomechanical factors influenced magmatic activity in the Bight Basin. Linear statistical analyses reveal a strong northwest–southeast alignment between extrusive features and the strikes of normal faults. Using Quaternary volcanic features within onshore southeastern Australia as analogues, we examine the role that the contemporary stress field at the time of magmatism played on the localisation of volcanic activity, with our findings suggesting that the orientation of maximum horizontal stress within the Bright Basin has remained consistent since the middle Eocene.

Abstract More than 3 m.y. of mafic volcanism near the Goat Rocks volcanic cluster in the southern Washington Cascade Range, USA, lends insight into the evolution of basalts and the subarc mantle at a long-lived, major arc volcanic locus. We contribute field observations, 40Ar/39Ar dates, paleomagnetic directions, and bulk rock and mineral compositions to characterize nine mafic units that erupted in association with the Goat Rocks volcanic cluster. The time frame of mafic volcanism, ca. 3.6 Ma to 60 ka, encompasses the lifespan of the central volcanic cluster (3.1 Ma to 115 ka), with a lull from ca. 2.7 Ma to 1.4 Ma. A climactic period of voluminous mafic activity and far-traveled lava flows, including construction of the Hogback Mountain shield volcano, coincided with voluminous andesite eruptions from the central volcanic cluster. The basaltic rocks in the Goat Rocks area are calc-alkaline to barely tholeiitic and have high field strength element depletion relative to large-ion lithophile elements characteristic of calc-alkaline basalts (CAB) of the Cascade volcanic arc. Unlike at neighboring andesitic volcanic centers (Mounts Adams, St. Helens, and Rainier), no other mafic end members such as high-aluminum olivine tholeiite (HAOT) or intraplate-type basalt (IPB) are present at or near the Goat Rocks volcanic cluster, although some of the calc-alkaline basalts in this study have IPB-like affinities. The Goat Rocks mafic units exhibit two main temporal trends in composition: (1) the most primitive basalts erupted earlier, compared to less primitive and more evolved compositions later, and (2) high field strength element concentrations are higher in the younger basalt units relative to the oldest two. In contrast to these temporal trends, the mafic units define two compositional groups that recur through time, a low-Sr and a high-Sr group, each with distinct trace element and Sr and Nd isotope ratios. Although radiogenic isotope ratios are generally aligned with High Cascades CAB and HAOT, some extend toward IPB of Mount Adams and Simcoe Mountains volcanic field. Olivine-dominated crystal fractionation at shallow pressure from a small range of parent magma compositions accounts for much of the variation among the basalts and basaltic andesites. A high-pressure fractionation model is plausible for only one of the youngest basalt units (basalt of Walupt Lake volcano). Mafic recharge and crustal assimilation accounts for the incompatible-element enriched composition of basaltic andesites erupted during construction of the largest andesitic centers, further supporting sustained basalt mass flux and thermal energy driving andesite genesis. We model the most primitive members of the Goat Rocks mafic units as partial melts of successively less depleted mantle in time. Variable degrees of fluxing with fluids and melts from subduction explain the distinction between high-Sr and low-Sr groups. We propose that mantle metasomatism by ancestral subduction and fluid-flux melting is heterogeneously distributed through the local subarc mantle and played a greater role in the genesis of the high-Sr basalt group. The limited range of primitive basalt types around the Goat Rocks volcanic cluster contrasts with the much greater diversity of basalts throughout the southern Washington to northern Oregon Cascade arc. On the other hand, the central volcanic cluster encompasses nearly the entire diversity observed at neighboring composite volcanoes. In the case of the Goat Rocks area at least, and perhaps attributable to the entire region, this means that the genesis of diverse intermediate magmas is independent from and does not require vastly different parental basalt compositions.

The petrology and geochemistry of the Montagna Grande-Monte Gibele trachytic shield volcano (Pantelleria, Italy)

SUMMARY The role of pre-existing lithospheric heterogeneities in rifting processes remains unclear. The Eastern and Main Ethiopian rifts lie within the same geodynamic province and are kinematically connected through the Turkana Depression, but they transect heterogeneous lithosphere: Pan-African accreted terranes, failed Mesozoic-Paleogene rift systems, zones of Eocene–Oligocene flood magmatism. Rifting in these pre-extension heterogeneities offers the opportunity to evaluate their relative importance in Oligo-Miocene to Recent stretching and magmatism. We use 3-D Rayleigh shear-wave speed (Vs) models inverted from ambient noise signals recorded on a temporary seismic network to image heterogeneities in lithospheric structure, and to evaluate their influence on syn-rift faulting and magmatism. Crustal feeder zones for Eocene–Oligocene flood magmatism in southwestern Ethiopia are marked by ≤50 km-wide, 10–15 km-thick mid-lower crustal fast wave speed (Vs ≥ 3.8 km s−1) anomalies that are localized rather than widespread. Evidence for active magma intrusions only occurs beneath aligned chains of Quaternary eruptive centres in Lake Turkana and ≤1 Ma shield volcanoes east of the Turkana rift having localized low Vs (≤3.4 km s−1) at 0–20 km depth. Evidence for widespread lower crustal intrusions, however, is lacking. Pan-African oceanic accreted terranes in southern Ethiopia have high Vs anomalies of 3.6 km s−1 throughout the crust and overlay previously imaged high-wave speed lithospheric mantle that has been interpreted as cold and strong Proterozoic accreted terrane. The integrated strength of this lithospheric-scale pre-existing mechanical heterogeneity resisted Oligocene–Miocene stretching and subsequently contributed to the unusual breadth of this East African rift sector lying north of the Turkana Depression.

Abstract The Medusae Fossae Formation (MFF) covers a region of Mars located to the southwest of the Olympus Mons shield volcano. The nature of this formation has been under debate for over 30 years. In order to better understand the MFF, we investigated scour pits or V‐shaped depressions carved into many places across the MFF. We quantified the number and distribution of the scour pits, their length, width, and orientation, and classified them into distinct morphologies: central peak‐scour pits, barchan‐shaped scour pits, and asymmetric scour pits. We hypothesize that scour pits initially develop as central peak scour pits when wind carves the area around a more resistant obstacle. Therefore, the orientation of the scour pit reflects the orientation of the formative winds. In this study, we found that scour pits in the MFF have similar orientations and morphologies to scour pits found in the north, west, and southwestern flanks of Olympus Mons. These similarities suggest that the scour pits in the MFF and around Olympus Mons are carved into similar materials. We propose that the MFF material extends up to the Olympus Mons region, leading to more MFF material exposed near Olympus Mons than previously mapped. The distribution of scour pits and proximity to Olympus Mons supports previous interpretations that the MFF is pyroclastic in origin.

El volcán San Martín Tuxtla es un volcán basáltico de escudo (SMTV) en el campo volcánico de Los Tuxtlas (LTVF), Veracruz, México. El volcán presentó erupciones explosivas en 1793, y presumiblemente en 1664, sin actividad premonitoria sentida por la población aledaña. La actividad de 1793, en particular, consistió en varias etapas de fuertes fases estrombolianas en la que se esparcieron grandes cantidades de ceniza volcánica que llenaron de temor a los habitantes de la región. A pesar de estos antecedentes, actualmente no se realiza ninguna vigilancia del volcán. Para obtener información básica sobre las condiciones internas del volcán, presentamos los resultados de los análisis de registros sísmicos de tres sismógrafos de banda ancha desplegadas alrededor del San Martín Tuxtla durante el periodo 2007-2013. Se registraron claramente unos 60 microsismos con magnitudes de entre 0.2 y 2.4. Veinticinco de los eventos mencionados fueron relocalizados con el método de doble diferencia para mejorar su localización. Además, se obtuvo el mecanismo focal de nueve eventos mediante el ajuste de la onda S. Los datos del SSN y las características de nueve terremotos moderados con focos en las proximidades de LTVF se incluyen como antecedentes sobre la sismicidad en la región. Los resultados son de utilidad para comparar la actividad que pudiera presentarse en caso de una reactivación del volcán y para la planificación del monitoreo de la actividad volcánica en el volcán San Martín Tuxtla.

This study examines groundwater flow paths and geochemical processes in the Piton des Neiges volcano on Reunion Island. Using data from the Salazie Amont tunnel, bored at a depth of 1000 m under the planèze of Plaine des Fougères, we characterise groundwater composition and weathering processes in volcanic terrains. The study area features high permeability in shallow lava flows, enabling deep water infiltration, but also demonstrates a decrease in permeability with increasing depth due to mineral precipitation of secondary phases, mainly clays. Reactive transport in the vadose and phreatic zones was modelled with KIRMAT, a geochemical code simulating water–rock interactions. Initial rainwater undergoes chemical changes while percolating through volcanic rock, increasing in pH and mineral content. In the phreatic zone, simulation results suggested magmatic CO 2 input, impacting water pH and mineral composition. The model captured observed mineral trends effectively, predicting significant secondary mineral formation at depth, particularly clay minerals. Results illustrate how mineralisation reduces permeability in volcanic formations over time, progressively creating an impermeable barrier in the volcano’s core. This research provides insights into the long-term evolution of groundwater systems in shield volcanoes, contributing to the understanding of aquifer dynamics and material flow in volcanic environments.

As the Pacific Plate migrates over the mantle plume below Hawai'i, magma flux decreases, resulting in changes in eruptive volume, style, and composition. It is thought that melt storage becomes deeper and ephemeral with the transition from highly voluminous tholeiitic (shield stage) to the less voluminous alkaline (post-shield and rejuvenation stages) magmatism. To quantitatively test this, we applied high-precision fluid inclusion barometry via Raman spectroscopy to samples from representative volcanoes of different evolutionary stages. This suggests an evolution from shield-stage shallow magma storage (~1 to 2kilometers) for Kīlauea to a post-shield stage that includes crustal magma storage within the volcanic edifice (~2kilometers) and deeper storage below the Moho (~20 to 27kilometers) for Haleakalā. The rejuvenation stage (Diamond Head) displays mantle-dominated storage (~22 to 30kilometers). High melt fluxes likely form stable conduits from the mantle to a shallow reservoir in the shield volcanoes. As melt flux decreases, the Moho becomes the boundary controlling melt stagnation and evolution.

Abstract We identified a ∼31 km diameter caldera with a well‐developed ring fault and ring dike structure at the Gardner shield volcano. Using Chandrayaan‐1 Moon Mineralogy Mapper (M3) and Lunar Reconnaissance Orbiter (LRO) Diviner data, we investigated 15 effusive flow units and an explosive unit. Spectral analysis revealed compositional similarities between effusive and explosive eruptions, indicating a single sourced magmatic eruption. Detailed hyperspectral and multispectral analyses (visible, near‐infrared, thermal infrared, and radar) indicate the presence of explosive pyroclastic material in the central part of the shield. We identified key morphological structures at the Gardner shield, including three major faults, the caldera's ring fault and ring dike structure, subsidence and resurgence crustal blocks, a graben, a parasitic cone, and extended lineaments beyond the previous work. Our analysis indicates that the well‐developed Gardner caldera exhibits lower subsidence compared to Earth's calderas, likely due to the Moon's lower gravity and lower crustal density. These surficial structures preserve the evidence of subsurface magmatic chamber dynamics, making the Gardner shield a unique location for understanding the thermophysical evolution of a central vent shield regime on the Moon. We describe six evolutionary stages, evidenced by multiple volcano‐tectonic structures, two distinct eruption styles, and the shield's relationship with the subsurface magmatic chamber, revealing a thermophysical evolution of a central‐vent polygenetic shield volcano on the Moon, following a formation mechanism similar to those observed in the shield volcanoes on Earth and Mars.

Abstract Venus' surface hosts many volcanic and tectonic features, among which coronae are widespread. Despite their inferred significance for Venus' geodynamics, existing corona databases have been incomplete and/or inaccessible. Here, we present an updated database of coronae, which integrates and validates existing data sets while incorporating new insights. We define coronae using the criteria: (a) presence of a (partial/full) annulus of closely spaced concentric fractures, (b) with or without corresponding quasi‐circular topographic relief, and (c) a minimum diameter of 60 km. Using this systematic approach, our database includes 740 corona features. We assess 507 to be Type 1 (fracture annuli 180°) and 233 as Type 2 (fracture annuli 180°) coronae. We identify subsets that share morphological traits with specific volcanic structures: 26 coronae show fracture annuli around domal shield volcanoes (Mons), and 112 features resemble large, collapsed caldera volcanoes or paterae. We also recognize a separate 46 “inter‐tessera corona‐like features” within the complex tesserae, which share similar morphological characteristics and have received little previous attention. We provide an analysis of the spatial distribution of coronae and examine their geological setting, topographic profiles, and lithospheric properties. We establish 11 topographic groups that can describe the diverse coronae. 26.4% of coronae display an elevated rim surrounding a depressed interior, while over 20% feature a full or partial trough. By linking the lithospheric and geological properties with corona morphologies, our study offers a deeper understanding of the diversity of coronae. Ultimately, this database provides a foundation for future investigations into the planet's geological evolution and surface activity.

Geological history of Samodiva Mons shield volcano, and surrounding area, Quadrangle V-29, Venus

Abstract Atla Regio is a large topographic rise, at the equator of Venus, considered to sit above a young mantle upwelling. Hosting several giant shield volcanoes, including Maat Mons, it is a strong candidate for recent eruptive activity. Through detailed analysis of material units and structures at Ozza, Maat and Sapas Mons, northern Dali Chasma and the surrounding plains, we have unraveled the tectono‐magmatic evolution at Atla Regio. Lithostratigraphic analysis, of the volcanic styles, lava flow relationships, rift–associated shield clusters, graben‐fissure systems and pit cratering, in relation to the regional plains and other older features, has enabled the establishment of a model of the evolution of volcanism. Structural analysis reveals that graben‐fissure systems at Ozza Mons transition outward into three major rifts, and two new, unnamed volcanoes are identified. Our model is evidenced by analysis of lava flow stratigraphy and cross‐cutting relationships with respect to the stratigraphic marker provided by the ejecta halo of the Uvaysi impact, and using sound stratigraphic principles. A relative chronostratigraphic framework for the area around Ozza and Maat Mons has thus been constructed, and our findings are in agreement with prior research. A new regional history is proposed here, where volcanism was initially concentrated along Dali Chasma, before plume volcanism took over at Ozza Mons and finally, Maat Mons became the most recent locus of volcanism. We propose that the pattern of large shield volcanoes with displaced centers here is indicative of minor crustal adjustments above a relatively long‐lived mantle plume.

We report observations and monitoring of sinkholes and tensional fissures occurring along the outer margin of the lava shield within Vesturbunki, one of Surtsey’s two tuff cones. The features were first noted in summer 2015 and traced nearly continuously along roughly 500 m of the lava–tuff contact. In 2015, 49 sinkholes and fissures were observed; subsequent field work in 2017, 2019 and 2025 recorded approximately 20 features per visit, including some previously unrecorded openings. Field data includes GPS locations and photographs. To contextualize these observations, we compare them with geodetic and seismic data from the area and report maximum surface temperatures for the two tuff cones, Vesturbunki and Austurbunki, from surveys we conducted between 2008 and 2025. Earlier geodetic data on Surtsey indicates ongoing subsidence of the island, with a decaying rate since the eruption and Austurbunki is more stable than Vesturbunki. Seismicity near Surtsey during the years 2009–2024 was examined and was found to be low to moderate with five events ≥M 2.5. The seismic hypocentre locations are uncertain because of sparse station coverage. Surface temperature monitoring shows Vesturbunki is consistently hotter, up to 100°C, and fluctuates by up to 4.5°C between measurements, while Austurbunki is stabler and slightly cooler, up to 96°C, with only 2°C fluctuations. The sinkholes were likely produced and maintained by a combination of island-wide subsidence, local compaction of volcanogenic material, and possibly by seismicity that may trigger opening of fissures in the palagonite tuff cone that enhance upward heat flow locally and temporarily. Continued monitoring and mapping, as well as installation of a local seismic station on Surtsey, is recommended to better resolve the processes that produce these features.