The transition and coexistence of large polygenetic volcanoes and monogenetic volcanic fields represents a key challenge in understanding crustal magmatism and volcanic evolution across active tectonic regions worldwide. This duality is strikingly exemplified in central Mexico. Here, the active polygenetic volcano Popocatépetl, coexists with the Chichinautzin Monogenetic Volcanic Field (CMVF), characterized by numerous small cones and lava flows reflecting short-lived, episodic eruptions. Although both volcanic styles are extensively documented individually, the fundamental tectonic and structural factors controlling their coexistence and transtition remain poorly understood. Our study aims to understand the influence of regional tectonic stress orientation and local faulting in interpreting the mechanisms that governs eruptive style transitions.

We integrated high-resolution structural mapping, remote sensing, and a 30-year seismic record (1994–2025). Fault and lineament patterns were derived from LiDAR Digital Elevation Models (DEMs) and Sentinel-1 SAR imagery, processed through slope, azimuthal, and contour analyses. These datasets were correlated with volcanotectonic (VT) earthquake records from Popocatépetl and CMVF to assess the spatial and temporal distribution of seismicity in relation to fault systems.

Our results delineate two major tectonic domains: (1) NW–SE and NE–SW fault systems characterizing the Popocatépetl volcano; and (2) a predominant E–W system defining cone alignments within the CMVF. Monogenetic cones in the CMVF align preferentially along E–W and NE–SW faults, reflecting a prevailing N–S minimum horizontal stress that facilitates direct magma ascent. In contrast, Popocatépetl is dissected by multiple, interacting, high-angle fault systems, including the active Tlamacas (NE–SW) and Nexpayantla (NW–SE) faults. The majority of pre-eruptive and co-eruptive VT earthquakes cluster along these structures, confirming their critical role in magma ascent, storage, and edifice segmentation.

We conclude that the coexistence and transition between polygenetic and monogenetic volcanism in central Mexico are fundamentally governed by the complexity and orientation of regional and local stress fields. In the CMVF, single stress regimes create efficient pathways for rapid magma ascent, favoring monogenetic activity. At Popocatépetl, intersecting and structurally complex fault systems induce magma trapping and long-term storage, driving polygenetic evolution.

How to cite: Sandoval García, M. and Martin-Del-Pozzo, A. L.: What controls the transition from monogenetic to polygenetic volcanism? Structural insights into the coexistence and transition between Chichinautzin Monogenetic Volcanic Field and Popocatépetl volcano, Mexico., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-574, https://doi.org/10.5194/egusphere-egu26-574, 2026.

Dokdo and Ulleungdo are volcanic edifices developed in the East Sea and show a clear contrast in their formation ages and evolutionary processes. The Dokdo volcano is an eroded volcanic edifice characterized by a flat summit at a water depth of approximately 200 m, forming a guyot-type morphology with small islets. The summit area reaches ~84.6 km² and is larger than the subaerial area of Ulleungdo. Approximately six levels of submarine terraces are developed on the summit, reflecting repeated Quaternary sea-level fluctuations. Bedrock exposure is dominant in the northern summit, whereas the southern part is sediment-rich, and an east–west alignment of small craters suggests the directional control of late-stage volcanic activity. The Dokdo volcano can be subdivided into a flat summit, a steep flank, and a gently sloping base. The flanks are characterized by submarine canyons and ridges with various orientations. Slope analysis indicates very steep gradients of up to ~27–30° along the canyons, implying repeated sediment transport and mass-movement processes. In the northern basal area, small cone-shaped positive reliefs are observed, and backscatter data indicate a mixture of exposed bedrock and sediment-covered surfaces. In contrast, Ulleungdo represents a relatively young, single-cone submarine volcano with a central volcanic island and steep flanks descending to depths of ~2,200 m. Radial lava ridges and lava fields are developed down to ~200 m water depth, while submarine canyons and debris lobes formed by repeated slope failures are concentrated between 600 and 1,200 m. The volcanic base consists of deep-sea sediment fans formed by gravity flows and turbidity currents, and only two levels of submarine terraces are developed on the continental shelf, in clear contrast to the multi-level terraces of Dokdo. Between Dokdo and Ulleungdo, the Anyongbok Seamount, with a summit depth of ~473 m, shows a pointed conical morphology without a wave-cut platform and a dominant north–south ridge. The concave summit geometry suggests the presence of a collapsed crater. Based on radiometric ages and geomorphic characteristics, the submarine volcanic edifices in the East Sea are inferred to have formed sequentially from Dokdo to Anyongbok Seamount and finally to Ulleungdo. These contrasting geomorphic features provide important constraints on the timing, eruptive styles, and spatiotemporal evolution of submarine volcanism in the East Sea.

How to cite: Kim, C. H., Choi, S. Y., Kim, W. H., Do, J. D., and Lee, B. G.: Submarine Geomorphology and Evolution of the Dokdo and Ulleung Volcanic Edifices in the East Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2387, https://doi.org/10.5194/egusphere-egu26-2387, 2026.

Karthala (Ngazidja Island, Comoros archipelago), an active basaltic volcano in the Indian Ocean, provides an excellent natural laboratory for studying the geomorphic evolution of a rapidly evolving caldera complex. Eruptive events in 2005–2006 reached a VEI 3 and emplaced fresh tephra and lava across the summit area, covering the cratered region and creating a time-zero surface for tracking post-eruptive erosion and drainage network development. Karthala’s craters are also shaped by mass-wasting processes, evidenced by landslide deposits in the craters that are visible in satellite and aerial imagery.

In this study, we construct a geomorphic chronology that spans 76 years using a combination of photogrammetry from a 2025 Unoccupied Aerial System (UAS) survey, Pléiades satellite imagery (2015, 2024), and orthorectified historical photographs (1949, 1961). This interval includes significant eruptions in 1952, 1965, 1972, 1991, and 2005-2007. We primarily focus on geomorphic change since the 2005–2006 eruptions, measuring erosion within the tephra-mantled summit region and mapping the temporal evolution of fluvial channel networks. By tracking the development of the drainage network, we can precisely constrain landscape response times and quantify the timescales at which volcaniclastic material is mobilized and redistributed in the landscape. In addition, we evaluate crater rim retreat and map collapse structures through time to explore how mass wasting interacts and competes with fluvial processes. Together, this work provides constraints on the timescales and relative importance of erosional processes that shape Karthala’s summit region between eruptive events, while placing its recent evolution in the context of crater changes that have occurred over decadal timescales.

How to cite: Guryan, G., Gourbet, L., Zorn, E., Villeneuve, N., Delcher, E., Soulé, H., Mogne Ali, M., Said Abdallah, C., Mohamed, W., and Mlanaoindrou, Q.: Geomorphic Evolution of Karthala’s Summit Caldera: Insights from Photogrammetry, Satellite Imagery, and Historical Aerial Photographs , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11515, https://doi.org/10.5194/egusphere-egu26-11515, 2026.

This preliminary study addresses the architecture of the magmatic plumbing system in southeastern El Salvador, where a cluster of recent monogenetic volcanic centers is spatially associated with the Intipuca Fault. This fault is part of the active shear zone located at the volcanic arc accommodating the right lateral motion of the fore-arc sliver with respect to the Caribbean plate in the context of the Cocos plate subduction in the Middle America Trench. The Intipuca fault acts as a link between the El Salvador Fault Zone (ESFZ) and the extensional domain of the Gulf of Fonseca and the Nicaraguan depression.

Four representative lava samples were analysed: three from monogenetic volcanoes emplaced along the fault and one from the underlying Pliocene stratovolcano of the Bálsamo Formation. Detailed petrography, electron microprobe analyses of phenocryst and groundmass minerals in each sample, and Ar/Ar geochronology were performed.

Preliminary results reveal mineralogical and textural differences between lavas from the monogenetic cones and the stratovolcano. The latter are dominated by plagioclase, with abundant small olivine and minor, but large (phenocrystic) pyroxene, and lack hydrated minerals. Some plagioclase macrocrysts display abundant disequilibrium textures, including resorbed plagioclase cores and sieve textures, suggesting prolonged crustal residence and magma recirculation under dry conditions.

Monogenetic lavas are characterized by abundant pyroxene meso- and macrocrysts. Plagioclase shows a range of sizes, some crystals showing disequilibrium features while others are apparently in equilibrium (continuous oscillatory zoning and euhedral shape Olivine is subordinate, commonly with oxidized rims and replacement coronas of pyroxene and plagioclase. Opaque minerals are also common, and minor, subhedral green amphibole occurs locally. The occurrence of hydrated minerals in the monogenetic lavas reflects rapid magma ascent along the Intipuca Fault, which likely acted as a preferential conduit preserving fluids derived from Cocos Plate subduction.

Similar spatial associations between monogenetic volcanism and transtensional faults have been documented in fault systems with comparable orientations near the Gulf of Fonseca. Likewise, monogenetic alignments are identified in association with segments with a dominant E–W strike (between N90°E and N110°E) that characterizes the El Salvador Fault Zone (ESFZ). This supports the idea that strike-slip fault systems play a fundamental role in modulating magma plumbing architectures and controlling the spatial distribution of monogenetic volcanism in subduction-related volcanic arcs.

How to cite: Comas, N., Álvarez-Gómez, J. A., de Ignacio, C., Martínez-Díaz, J. J., and Hernández, W.: Structural control on monogenetic volcanism along the Intipuca Fault, Central America Volcanic Arc, El Salvador, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11915, https://doi.org/10.5194/egusphere-egu26-11915, 2026.

In south-western Martinique (Lesser Antilles), the basaltic lava flow and associated strombolian cone of Pointe Burgos transect the porphyritic dacitic lava dome of Morne Champagne, which has been dated to 617 ± 52 ka (Germa et al., 2011). A striking characteristic of the basaltic lava is an unusually high abundance (~4%) of large quartz crystals reaching up to 2 cm. These have previously been interpreted as xenocrysts incorporated into the basaltic magma through mechanical mixing with a shallow, cooled dacitic reservoir at an approximate 9:1 basalt–dacite ratio. Support for this interpretation includes resorbed plagioclase phenocrysts with reaction rims, commonly regarded as indicators of crystal remobilisation. However, the eruption products lack other textural features typically associated with magma mixing. Moreover, the quartz crystals display atypical morphologies, extensive internal fracturing, and occur as apparent void-fillings within the basalt, prompting a reassessment of their origin.

To better constrain the timing and mechanism of quartz incorporation, we investigated both the eruption age of the basaltic lava and the formation history of the quartz crystals. K–Ar dating of the basaltic groundmass yields an age of 379 ± 25 ka, indicating that the basalt erupted ~240 ka after the dacitic dome it crosscuts. This substantial time gap implies that the shallow dacitic reservoir would have been fully solidified during basalt ascent, a scenario in which entrainment of dacitic enclaves might be expected but is not observed.

Thermoluminescence (TL) dating provides a means to estimate the time elapsed since mineral crystallisation or cooling to ambient temperature, rendering it well suited to evaluate whether the quartz formed contemporaneously with the basaltic eruption or represents a later generation of minerals (substitution minerals or hydrothermal void fillings). Moreover, TL can inform on thermal conditions during signal acquisition through the thermal stability of selected TL signals. We applied red TL measurements using multiple dose determination protocols to calculate an apparent age, which yielded internally consistent results. Dose-rate calculations account for the grain-size distribution of the quartz xenocrysts, radioelement concentrations and the erosional evolution of the site.

Apparent TL ages range from ~104 ka assuming no erosion, to ~122 ka for ~100 m of surface erosion, each with an ~17% uncertainty. New LA-ICP-MS geochemical data obtained from three quartz xenocrysts provide further evidence for a magmatic formation environment, lending support to the magma mixing hypothesis. The younger TL ages relative to the K–Ar eruption age may thus reflect partial thermal resetting of the TL signal due to prolonged hydrothermal activity. Kinetic parameters derived from the TL data enable forward modelling of thermal scenarios compatible with the observed ages. Together, the geochronological, kinetic, and geochemical results allow us to reassess the origin of quartz in the Pointe Burgos lava and to explore the post-eruptive hydrothermal evolution of the system.

References

Germa, A., Quidelleur, X., Lahitte, P., Labanieh, S., Chauvel, C., 2011. The K–Ar Cassignol–Gillot technique applied to western Martinique lavas: a record of Lesser Antilles arc activity from 2 Ma to Mount Pelée volcanism. Quaternary Geochronology 6, 341-355.

How to cite: Schmidt, C., Germa, A., Quidelleur, X., King, G., and Jaimes-Gutierrez, R.: Constraining eruption age and quartz formation in a basaltic lava flow (Martinique) using trapped-charge and geochemical methods , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14547, https://doi.org/10.5194/egusphere-egu26-14547, 2026.

It is important to accumulate research examples on the spatial distribution of volcanic conduits and dikes under volcanic edifices that served as magma migration pathways, and eruptive volume of past activity, for risk assessment in volcanic disaster prevention. Particularly for volcanoes where the distribution of volcanic conduits and the eruptive volume of activity have not been clearly elucidated in detail, assessing their risk is difficult. Therefore, developing a quantitative and uniform assessing method applicable to each volcano is desirable. However, determining the distribution of volcanic conduits and dikes under volcanic edifices is challenging. Furthermore, estimating the eruptive volume of volcanic activity, requires detailed geological surveys, leading to insufficient estimates for some volcanoes.

The topography of a volcanic edifice is generally thought to reflect the location of magma intrusion associated with volcanic activity and its history (e.g., Nakamura, 1977). Therefore, we are developing a method to determine the predominant orientation of radial dikes under volcanic edifices and evaluate the long-term stability of central conduit locations using topographic analysis with GIS and 10m DEM (Nishiyama et al., 2023). Furthermore, we are attempting to develop a method to estimate the location of a center of activity and the eruptive volume of its activity using topographic data. The development of these topographic data-based evaluation methods is expected to provide useful objective baseline data for conducting detailed investigations on volcanoes that have not yet been studied in depth. This presentation introduces the content of our attempts using topographic analysis.

This study was funded by the Ministry of Economy, Trade and Industry (METI), Japan as part of its R&D supporting program for the geological disposal of high-level radioactive waste (JPJ007597).

[References] Nakamura, 1977, JVGR., 2, 1-16. Nishiyama et al., 2023, JSEG, 64(3), 98-111.

How to cite: Nishiyama, N., Kato, Y., Kawamura, M., and Umeda, K.: Attempt to estimate the center of activity and scale of Quaternary volcanoes through topographic analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15548, https://doi.org/10.5194/egusphere-egu26-15548, 2026.

The Lessini Mountains volcanic district (Venetian Prealps, Italy), belonging to the Veneto Volcanic Province, is mainly composed of Paleogene basaltic volcanics in complex stratigraphic and tectonic relationships with a Meso-Cenozoic sedimentary succession of a shallow-marine environment. The geological framework was shaped by extensional tectonics, with N–S-trending faults such as the Castelvero Fault, which separates the mafic rocks to the east from the carbonate lithologies to the west. The volcanic succession is characterized by a relative lithological homogeneity of basic volcanic products and by discontinuous outcrops due to dense vegetation and agricultural cover. Consequently, detailed reconstruction of the internal stratigraphy based on field data alone is challenging and requires further investigation to identify stratigraphic reference horizons. Overall, the succession records a transition from submarine to subaerial volcanism (Barbieri et al., 1991; Brombin et al., 2019). The lower portion is characterized by basaltic deposits emplaced in a marine environment (i.e., hyaloclastites to lava flows of fissural eruptions), frequently intercalated with Nummulitic Limestones which testify to phases of quiescence of the volcanic activity. The upper portion reflects the establishment of predominantly subaerial conditions, with the growth of shield volcanoes. Above the last nummulitic level (the Roncà Horizon), marking the base of the upper part of the volcanic sequence, the internal stratigraphy remains poorly constrained, as no laterally continuous stratigraphic markers have been recognized so far. This study focuses on this part of the volcanic succession, exposed along the ridges between Alpone Valley and Agno Valley, through the integration of remote-sensing analyses and detailed field observations. In recent years, the increasing availability, quality, and spatial resolution of remote-sensing data have made geomorphological analyses based on Digital Terrain Models (DTMs) an increasingly important complement to traditional geological investigations. Among the available visualization techniques, the Red Relief Image Map (RRIM) method has proven particularly effective in highlighting subtle morphological variations in volcanic terrains (Chiba et al., 2008; Favalli & Fornaciai, 2017). Within the framework of the CARG Project (Sheet 124 – Verona Est), RRIM-based geomorphological analysis integrated with detailed fieldwork provides new constraints on the stratigraphic reconstruction of the upper volcanic succession of the Lessini Mountains. A key result is the recognition of a decametre-thick volcaniclastic sedimentary level, mapped as the Cortivo Unit, clearly detectable in RRIM by its association wiht areas of lower slope gradients. This unit records a significant phase of volcanic quiescence, during which erosion, transport, and deposition processes led to the reworking of previously emplaced basaltic rocks. It therefore represents a stratigraphic hiatus and a marker horizon that subdivides the succession into a lower unit predating and an upper unit postdating the Cortivo Unit. Future geochemical and petrographic analyses and radiometric dating will allow calibration and refinement of the reconstructed stratigraphic framework.

How to cite: Cavallina, C., Sonia, S., Magli, A., Lucchi, F., José Pablo, S., Matteo, R., and Giulio, V.: Insights into the Eocene stratigraphic succession of the Lessini Mountains volcanic district by integrating field geology and geomorphological interpretation of Red Relief Image Maps from high resolution DTM (CARG Project, Sheet 124, Verona Est, Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20022, https://doi.org/10.5194/egusphere-egu26-20022, 2026.

For decades, the Hallmundarhraun lava has been categorized as a historic lava, i.e. postdating the Landnám tephra layer (LNL) from AD 877. In the summer of 2024, the LNL was found on top of the lava, somewhat unexpectedly. In 2025, approximately twenty test pits were excavated to corroborate this initial finding. In all cases, the presence of the LNL was confirmed.

In connection with this study, a sample of barren plant remains was collected from beneath the lava and submitted for radiocarbon (¹⁴C) dating in Aarhus, Denmark.

The LNL is a widespread, two-coloured tephra, consisting of a lower light-coloured unit (c. 0.5 cm thick) of fine silicic pumice and an upper olive-green unit (1.5–2 cm thick) composed of basaltic glass shards. The LNL is one of the most important marker tephra layers in Iceland. It was found close to the lava surface, commonly separated from it by a 1–3 cm thick soil layer, although in some cases the soil cover was thinner.

In total, six distinct tephra layers were identified within the soil cover of the Hallmundarhraun lava. Samples from all layers were analysed chemically using an electron microprobe. The tephra layers younger than the LNL are, in descending order, H-1766, K-1721, H-1693, and H-1104. The oldest tephra layer identified is a black Katla tephra lying directly on top of the lava, with no intervening soil layer. This suggests that the Katla tephra and the lava are close in age.

A literature review was conducted to identify information that might constrain the age and distribution of this Katla tephra. Although the results were not conclusive, a possible correlation was identified with a widespread Katla tephra known as Hrafnkatla. This tephra has been identified in ice cores from the Greenland Ice Sheet and dated to AD 763 based on annual layer counting. The Katla tephra overlying the Hallmundarhraun lava may correlate with the Hrafnkatla tephra; however, as two other Katla tephra layers of similar age have been identified in soils and lake sediments, this correlation remains uncertain.

Taking all available evidence into account, the results indicate that the Hallmundarhraun lava most likely formed during the period AD 760–780. The radiocarbon dating supports this interpretation. Previously, the lava was thought to have formed between AD 910 and 950. The Hallmundarhraun eruption therefore predates the Norse settlement of Iceland in the mid-to-late 9th century, effectively excluding the possibility of eyewitness observations or contemporaneous written accounts.

How to cite: Sigurgeirsson, M. Á.: Revised age of the Hallmundarhraun lava, West Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20945, https://doi.org/10.5194/egusphere-egu26-20945, 2026.

Mount Etna, one of Earth's most active volcanoes, rises to an elevation of 3,400 meters. Its eastern flank extends seaward, descending to approximately 1,500 meters below sea level and creating a total vertical relief of nearly 5,000 meters. While it is known that Etna's offshore flank is highly mobile, the seafloor morphology and associated structures remain poorly understood.

During the 2024 RV METEOR cruise M198, high-resolution microbathymetry data were collected using an Autonomous Underwater Vehicle (AUV), and rock samples were dredged from distinctive morphological features. Using new AUV microbathymetry, we characterise a stiff layer that forms a narrow canyon in the Valle di Archirafi, featuring high relief and rough surfaces exposed by the erosion of overlying marine sediments. This layer is also forming in the upper part of the Amphitheatre, a chain of cliffs overlooking a gentler slope. The layer is characterised by a chaotic, high-amplitude facies in the seismic lines, which can be followed from the Valle di Archirafi to the Amphitheatre. Dredging during the M198 cruise enabled sampling phyric lavas in the upper part of the Amphitheatre and chemical analyses suggest cooling in a subaerial environment. These findings imply more than 600 m of subsidence of the entire area (42 km²). The area is located between 4 and 8 km from the coastline and lies directly beneath the Giarre wedge, which exhibits the highest sliding velocity on the eastern flank. This suggests that the offshore part exerts a strong pulling force on the northern part of Etna’s mobile sector and is thus key to understanding the dynamics of the onshore sector. In line with the onshore block structure inferred by geodetic methods, our new findings support a decoupling of a shallower block riding on top of the larger southeastern mobile flank. Finally, based on existing knowledge of Etna’s edifice, our new offshore interpretation, and existing seafloor morphology constraints, we propose an extended map of the offshore flank thickness. These new data necessitate a revised interpretation of the submarine structural model and challenge existing paradigms regarding the mobile flank.

How to cite: Mayolle, S., Urlaub, M., H. Hansteen, T., Madrigal, P., Campbell, M., Furst, S., Bonforte, A., and Gross, F.: Etna’s submarine flank morphology and basement: new insight from microbathymetry and revised structural interpretation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13865, https://doi.org/10.5194/egusphere-egu26-13865, 2026.

Extensional tectonic regimes often host volcanoes that produce highly hazardous, caldera-forming explosive eruptions. An example is the Santorini-Kolumbo volcanic centre on the continental South Aegean Volcanic Arc. The volcanic centre includes Santorini caldera, the submarine polygenetic Kolumbo Volcano to the northeast of Santorini,  and the linear zone of more than 20 smaller volcanic cones making up the Kolumbo Volcanic Chain. It is one of the most active eruptive centres on the South Aegean Volcanic Arc and experienced a period of unrest in 2024-2025. IODP Expedition 398 deep-drilled the volcano-sedimentary infills of submarine half-grabens around Santorini and on the western flank of Kolumbo in order to produce a high-resolution eruptive chronostratigraphy for the volcanic field, ground-truth seismic stratigraphy, and to extract an integrated timeline of interactions between the neighbouring volcanoes and volcano-tectonic couplings. In the new, more complete volcanic record, we: (1) recognise a transition of Santorini from moderately explosive, arc stratovolcano behaviour (~570 – 250 ka) to repeated caldera-forming behaviour (<250 ka), (2) identify 19 explosive eruptions of the KVC beginning at 265 ka with a lifespan-averaged recurrence time of explosive activity of ~6 k.y. (but as low as ~1 k.y. in certain time periods), (3) observe that the three main phases of edifice construction at Kolumbo (ca. 265–193 ka, 24 ka, and 0.4 ka) broadly correspond to the periods of caldera-forming eruptions at Santorini (186 ka – 177 ka and 22 ka – 3.6 ka). By ground-truthing seismic stratigraphy through core-seismic integration, we also produce a unique high-resolution record of volcanic activity and lithospheric extension for the volcanic field. This allows us to show that Santorini’s caldera-forming eruptions all lie above a seismic reflection onlap surface that records a phase of rapid rifting.  This phase of rapid rifting may have amplified the normal internal dynamics of the magmatic system driving the transition of Santorini from a prolonged state of arc stratovolcano behaviour to a state of repeated caldera-forming eruptions. In addition, the birth of Kolumbo coincided with the transition of Santorini to highly explosive activity, possibly due to joint interactions with the regional lithospheric stresses. Through our new integrated record, we show a possible example of rift modulation of an arc magmatic system on the 10⁴-10⁵ yr timescales typical of caldera cycles and the coupling of neighbouring volcanoes on 10⁴  yr timescales.

How to cite: Metcalfe, A., Druitt, T., Pank, K., Kutterolf, S., Preine, J., Nomikou, P., Hübscher, C., and Ronge, T. A. and the IODP Expedition 398 Scientists:  Temporal linkages of explosive activity on the South Aegean Volcanic Arc related to changing lithospheric stresses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17938, https://doi.org/10.5194/egusphere-egu26-17938, 2026.

The establishment of continuous volcanic time series is a key to understanding the volcanic evolution and behaviour of arc systems and volcanic complexes. Yet the establishment of continuous records is often hindered by incomplete volcanic archives on land due to erosion or inaccessibility of volcanic deposits. Growing steadily over the past decades, the field of marine tephra studies has shown great potential in overcoming these issues. As marine drilling techniques advance, they now enable the recovery of continuous and undisturbed marine sediment records, often even extending the volcanic onland records significantly further back in time. Drilling close to volcanically active environments, like volcanic arcs, provides the most complete eruptive archive possible and therefore allows us to unravel the volcanic and magmatic behaviour of volcanic systems over geologically long periods of time. Furthermore these long and continuous records enable multi-disciplinary studies, such as the establishment of volcano-tectonic or volcano-climate relationships.

IODP Expedition 398 drilled the marine sediments in the basins of the Christiana-Santorini-Kolumbo Volcanic Field (CSKVF) with the aim of expanding our knowledge of its volcanic evolution, and its interaction with tectonics and climate. The CSKVF belongs to the South Aegean Volcanic Arc (Greece), and particularly Santorini has been known for its highly explosive volcanism and caldera-forming eruptions since c. 250 ka that laid down the Thera Pyroclastic Formation (TPF). Before that, Santorini’s volcanic activity has been described as mainly effusive to weakly explosive forming the Peristeria stratocone (c. 530-430 ka) and the Early Centres of Akrotiri (c. 650-550 ka). However, IODP Expedition 398 identified a large submarine rhyolite deposit, the Archaeos Tuff (AT), interpreted as the product of a highly explosive submarine eruption of Santorini occurring at c. 765 ka, clearly pushing the boundaries of the unkown.

Here, we present the revised <765 ka tephrochronostratigraphy using the marine basin sediments drilled during IODP Expedition 398. Geochemical fingerprinting of tephras has enabled the identification of all known Plinian TPF eruptions, as well as numerous “new” explosive volcanic events within the TPF but also beyond. We have identified a total of 298 eruptions derived from Santorini and Kolumbo, and the established volcanic time series shows multiple tempos of arc volcanism, each about 250-300 kyr long. The eruptions range between magnitudes M2 to M6 throughout the record. However, the period <250 ka clearly stands out in terms of volcanic productivity and has produced about 3x more cumulative magma mass compared to the period 765-250 ka.

Our record fills the currently existing gap between Santorinis AT eruption at c. 765 ka and the onset of the TPF, and shows that Santorini was continuosly producing (highly) explosive eruptions. Furthermore, our findings highlight the importance of complementary and multi-disciplinary studies to reveal the most complete picture of arc volcanism.

How to cite: Pank, K., Metcalfe, A., Kutterolf, S., and Druitt, T. and the IODP Expedition 398 scientists: New insights on explosive volcanism at Santorini (South Aegean Volcanic Arc) based on marine sediments drilled during IODP Expedition 398., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18317, https://doi.org/10.5194/egusphere-egu26-18317, 2026.