Sea level rise (SLR) poses a major challenge for coastal regions of India, which host dense
populations, critical ecosystems, and vulnerable infrastructure. This study investigates the
spatial and temporal evolution of Sea Level Anomalies (SLA) along the eastern and western
coasts of India from 1995 to 2020 using satellite-derived gridded altimetry, along-track
measurements, and tide gauge data. SLA values show marked heterogeneity, with
consistently higher anomalies on the west coast (0.2 – 0.25 m) compared to the east coast
(0.1–0.15 m). Significant positive trends are observed across both coasts, ranging from
0.0075 to 0.01 m yr⁻¹, with a more uniform and accelerated rise after 2010.We used
multiple linear regression and Granger causality analysis to find the main causes of SLR.
Results indicate that CO₂ concentration (21.81 %) is the leading contributor to SLR on the
east coast, while sea surface temperature (21.36 %) exerts the strongest influence on the
west coast. Both methods reveal strong causal links from atmospheric warming, ocean heat
content, and cryospheric melt to regional sea level variability, which points to thermal
expansion as a key mechanism. Tide gauge observations similarly show rising sea levels at
most locations, with the west coast exhibiting a higher aggregated trend (6.78 ± 1.35 mm
yr⁻¹) than the east coast (1.91 ± 1.09 mm yr⁻¹).Future sea level projections using CMIP6
(CNRM-CM6-1HR) under SSP126, SSP245, and SSP585 scenarios suggest a substantial rise in
SLA by 2100, with larger increases along the east coast (0.4 – 0.55 m) compared to the west
coast (0.35 – 0.45 m). Although uncertainties in climate model performance remain, the
observed acceleration and consistent warming trends highlight significant risks for coastal
communities, ecosystems, and infrastructure. These findings point out the urgent need for
region-specific coastal adaptation and mitigation strategies.
How to cite: Kannaujiya, V. K., Rai, A. K., and Malakar, S.: Thermal Expansion or CO₂? Unveiling the Dominant Drivers of Sea Level Rise Along India’s Coasts Through Multivariate Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1061, https://doi.org/10.5194/egusphere-egu26-1061, 2026.
Turbidity currents and slope failures are common processes in subaqueous settings worldwide. Their deposits, turbidites and mass-transport complexes (MTCs), constitute some of the most important components of sedimentary basin infill. We integrate high-resolution 3D seismic reflection data covering c. 3000 km², 2D seismic data spanning 40,000 km², and two industry wells from the Taranaki Basin, NW New Zealand, to investigate the preconditioning and emplacement of slope failures in a turbidity current dominated slope setting. In study area, the post-Miocene succession contain a ~300 m thick, laterally continuous interval of cyclic steps that dominates the slope region, indicating that supercritical turbidity currents were the prevailing depositional process. Within this succession, we found at least eight seismically imaged MTCs (MTC-1 to MTC-8), which together account for more than 70% of the total volume within the turbidity current dominated interval.
MTC-6 is the largest one spans more than 1200 km² in area. It is overlain by MTC-7 and underlain by the pre-existing MTC-2 above late Miocene unconformity (~7 Ma). Internally, MTC-6 is characterized by large normal faults in the headwall zone, contractional thrusts in the toe zone, NNW-dipping longitudinal shear bands and widely distributed pockmarks in the proximal zone. MTC-6 contains giant extensional blocks (450-550 m high, 0.5-4 km long), contractional pressure ridges (250-450 m high, 0.2-1.3 km long), and vertical fluid conduits that intersect both the base and top surfaces of the MTC. However, these blocks exhibit limited horizontal transport distances (less than 10 km) and internally preserve well-defined cyclic-step bedforms that can be correlated from the toe to the headwall region.
We suggest that rapid aggradation and repeated grain-size sorting induced by supercritical turbidity currents promoted underconsolidation and inefficient drainage, leading to localised excess pore-pressure build-up between the MTC-2 and the base of the cyclic steps interval. This ultimately established a mechanically weak zone that preconditioned the subsequent emplacement of MTC-6. We attribute the triggering of MTC-6 to shear coupling with subsequent MTC-7. During emplacement of MTC-7, additional loading and basal traction generated stress perturbations that were transmitted downward and preferentially localised within the preconditioned weak zone of the cyclic steps interval, inducing transient excess pore pressure. Inefficient drainage further sustained this overpressure, reducing effective stress and allowing the weak zone to reach a critical failure threshold. Subsequently, the localised overpressure redistributed via fluid migration along the weak horizon, promoting shear-rupture propagation and enlarging the failure scale. However, because the shear-coupling perturbation imparted by the MTC-7 was limited in magnitude and duration, the transmitted basal shear stress was insufficient to sustain dynamic weakening, and the associated overpressure weakening likely decayed during subsequent drainage, thereby preventing long-distance transport.
Our results indicate that turbidity current dominated slope settings may be inherently prone to repetitive slope failures. Newly emplaced MTCs can cause remobilization of underlying thick-bedded turbidite successions through shear coupling. This mechanism may represent a previously underappreciated control on multi-phase slope instability in submarine sedimentary systems.
How to cite: Li, W. and Wu, N.: Shear Coupling as a Trigger Mechanism for Slope Failures in a Turbidity Current Dominated Slope, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4191, https://doi.org/10.5194/egusphere-egu26-4191, 2026.
Assessment of seismic and tsunami hazards along coastlines requires knowledge of past earthquakes and their recurrence times along active submarine faults. To this end, subaqueous paleoseismological studies are performed and are based on sediment cores and seismic reflection images of faults. However, local site conditions sometimes preclude coring or seismic surveys and, even when possible, the resulting data may be limited. In addition to traditional geophysical and sedimentological data, seafloor geophysical data from submersibles can help elucidate the paleoseismic history of submarine faults. Here, we conducted a near-bottom geological survey using a Remotely Operated Vehicle (ROV) along the Roseau normal fault (Lesser Antilles, France) to study the fine morphology and paleoseismic history of an active submarine fault scarp. This fault hosted the Mw 6.3 2004 Les Saintes earthquake and shows a coseismic ribbon at its base. We used the submersible data to map and characterize several scarp morphologies including abrasion bands, notches, roughness changes, dark bands, and uplifted sediments along the fault scarp. We propose that these markers, which all formed at the seafloor, can ultimately be used to reconstruct the exhumation history of the fault scarp, because they are linked to base level changes (i.e. sedimentation and tectonic exhumation). At one site along the Roseau fault, the scarp’s detailed morphology can be explained by the occurrence of three earthquakes coupled to several episodes of rapid sedimentation. The penultimate earthquake may have generated a vertical offset of 3 m, where at the same location the 2004 event slipped by ~1.4 m. The penultimate earthquake was at least as energetic as the 2004 event, the Roseau fault being able to host a M7 event if broken entirely. Sediment rates from cores sampled near the fault show that the penultimate earthquake probably occurred within the past ~2.8 kyr. These observations highlight the potential of studying offshore faults with ROV optical imagery to better understand the seismic history of crustal faults.
How to cite: Leclerc, F., Billant, J., Seibert, C., Escartin, J., Feuillet, N., Hughes, A., Schmidt, S., and Le Callonnec, L.: New insights into subaqueous paleoseismology from the preserved imprints of paleo-earthquake markers on a normal fault scarp (Roseau Fault Lesser Antilles, France), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2426, https://doi.org/10.5194/egusphere-egu26-2426, 2026.
The Cape Fear Landslide Complex offshore North Carolina is the largest and most-voluminous mass transport complex on the Eastern North American Margin. Despite its scale, preconditioning factors, trigger mechanisms, and emplacement processes responsible for its formation remain poorly constrained. Previous studies have proposed gas hydrate dissociation or salt diapirism as primary triggers, but these interpretations are largely based on spatial correlations rather than direct causal evidence.
Here, we use 2D multichannel seismic data collected on R/V Marcus G. Langseth in 2023 to reconstruct the processes that led to the formation of the Cape Fear Slide Complex. The data reveal vertical fluid migration pathways originating in Jurassic sediments within the thermogenic production zone, terminating directly below the uppermost landslide headwall on the continental slope. Seismic bright spots and amplitude-versus-offset responses indicate the presence of gas within and around these vertical fluid migration pathways, consistent with higher-order hydrocarbon anomalies in Ocean Drilling Program drill cores.
We propose that sustained vertical fluid migrations led to overpressure in shallow sediments, reducing effective stress and critically preconditioning the slope prior for failure. Furthermore, we identify multiple, spatially separated depositional lobes on the abyssal plane downslope from the headwall. This geometry suggests that the Cape Fear Slide Complex formed through distinct progradational and retrogradational phases rather than in one catastrophic failure event. This multi-phase emplacement style implies different magnitudes and recurrence characteristics for landslide-generated tsunami than previously assumed.
How to cite: Kühn, M., Bécel, A., Grall, J., Daigle, H., and Miller, N.: From rising fluids to multi-stage landslide emplacement: reconstructing the formation of the Cape Fear Slide Complex offshore North Carolina, US, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8157, https://doi.org/10.5194/egusphere-egu26-8157, 2026.
This study reconstructs the provenance and physical intensity of paleo-tsunami events by integrating organic microfossils, palynofacies, geochemical (coreXRF), and microbial eDNA analyses from core 20HH01, retrieved from Lagoon Hyangho on the eastern coast of Korea. While previous research identified Tsunami Event 1 (TE1, ca. 8.3 ka) linked to Ulleung Island’s volcanism, this study focuses on Tsunami Event 2 (TE2, ca. 6.5–7.8 ka) and Event 3 (TE3, ca. 0.3–2.5 ka), which exhibit distinct paleoenvironmental proxies.
TE2 is interpreted as one of the highest-energy tsunami inundation events recorded in the East Sea coastal region. This interval is characterized by a pronounced increase (>50%) in marine palynomorphs, including dinoflagellate cysts (Spiniferites spp.) and foraminiferal organic linings. Palynofacies analysis reveals poorly sorted, lath-shaped phytoclasts with low roundness, indicating rapid, high-energy landward sediment transport. A marked decline in pollen concentration is interpreted as a dilution effect caused by the rapid deposition of coarse sediments rather than regional vegetation collapse.
For TE3, we propose a novel geochemical and microbial linkage to volcanic activity at Mt. Baekdu. The sediment layer corresponding to the 946 CE “Millennium Eruption” exhibits a distinct enrichment in gallium (Ga) and elevated Ga/K ratios (exceeding 1.5 times background levels), coincident with the detection of the deep-sea hydrothermal bacterium Sulfurimonas f. These observations suggest a potential hazard cascade in which seismic disturbances associated with the Baekdu eruption may have triggered submarine mass failures and subsequent tsunami generation, while concurrently dispersing Ga-rich tephra across the East Sea.
Overall, this study highlights the value of coastal lagoon sediments as high-resolution archives of regional geohazards. The integration of microbial tracers and geochemical fingerprints, particularly Ga-based proxies, provides a robust framework for deciphering the origins and mechanisms of enigmatic paleo-tsunami events.
How to cite: Lee, H., Kim, Y., and Choi, Y.: Multi-proxy Reconstruction of Holocene Tsunami Events (TE2 and TE3) in a Coastal Lagoon, East Sea: Evidence for High-Energy Inundation and Volcanic-related Hazards, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8549, https://doi.org/10.5194/egusphere-egu26-8549, 2026.
Tsunamigenic landslides represent a major geohazard in the fjord environments of central West Greenland, induced by steep topographic reliefs and changing Arctic conditions. A dramatic example occurred on June 17th 2017, when a slope failure on the south-facing wall of Ummiammakku Mountain released a 38-40 × 10⁶ m³ rock avalanche into Karrat Fjord. The event generated a displacement wave with local runup heights exceeding 90 m and propagated 32 km southwest to the settlement of Nuugaatsiaq, causing severe infrastructure destruction and four fatalities. In this study we have integrated swath bathymetry and seismic datasets, along with sediment core information, to map mass-transport deposits produced by the 2017 rock avalanche in Karrat Fjord. By integrating geophysical imaging, lithofacies descriptions, XRF geochemistry, grain-size distributions, and 210Pb-dating, this study delineates the channelized runout of the 2017 event.
The increasing frequency of landslides in West Greenland has motivated new research into the climatic and cryospheric controls on slope instability. Although the region is tectonically stable with only minor earthquake activity, recent studies suggest a connection between warming climate, permafrost degradation, and enhanced slope failure. This hypothesis aligns with broader observations across polar margins that link rising temperatures, increased precipitation, and isostatic rebound with enhanced decreasing slope instability. Our findings demonstrate the value of high-resolution marine datasets for detecting offshore landslide deposits and contribute new insights into the temporal and spatial patterns of slope instability in a rapidly changing Arctic fjord system.
How to cite: Pérez, L. F., Nielsen, F. A., Knutz, P. C., Andersen, T. J., Andresen, C. S., Svennevig, K., Boldreel, L. O., and Fruergaard, M.: Sedimentary processes associated with recent landslides – Karrat Fjord 2017 case of study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8998, https://doi.org/10.5194/egusphere-egu26-8998, 2026.
Underwater landslides are associated with multiple geohazards, including tsunamis and damage to underwater infrastructure, but a lack of real-time observations of these events hinders our understanding of their development mechanisms. Analysis of ancient deposits from underwater landslides has the potential to address this by providing insights into landslide preconditioning and failure. Here, we map a hitherto understudied megaslide—the Stad Slide (~0.4 Ma)—within the North Sea Fan on the northern North Sea margin. The aims are to determine its distribution and thickness, analyse its morphological characteristics and contextual stratigraphy, and identify the factors that are likely to have preconditioned and triggered failure. A database comprising 42 500 km2 of high-resolution 3D seismic reflection data and a grid of 2D seismic-reflection profiles covering 150 000 km2 was used to map the Stad Slide in full for the first time. With a volume of ~4300 m3, the Stad Slide is revealed to be the largest megaslide by volume in the region and one of the largest slides by volume in the world. The broad timing of the Stad Slide (~ 0.4 Ma) aligns with enhanced glacial sedimentation in this region, which may have preconditioned failure by increasing overpressure in underlying sediments. The slide’s multiple headwalls suggest that its large volume was facilitated by multiple stages of failure along layers of glacimarine and contouritic sediment. Whilst the relationship between large slides and tsunamis is complex, the large volume of the Stad Slide suggests that it could have triggered a tsunami that affected the North Sea region. A ~200 m-thick contourite drift infills the slide headwalls, which potentially formed a weak layer for subsequent sliding in the North Sea Fan. As the Stad Slide marks the onset of repeated Quaternary megasliding in this region, this research advances our understanding of what causes and preconditions large-scale sediment failures on glaciated margins.
How to cite: Tiller, B., Batchelor, C., Bellwald, B., Winter, K., Ross, N., and Planke, S.: Stad Slide: extent, morphology, and drivers of one of the world’s largest submarine megaslides, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10011, https://doi.org/10.5194/egusphere-egu26-10011, 2026.
Megabeds, also known as "megaturbidites," are exceptionally large submarine sediment deposits likely formed by catastrophic geohazard events. These deposits are increasingly being identified with modern high-resolution geophysical data, yet their origins and characteristics remain debated. Five megabeds have been identified in the Marsili Basin of the Tyrrhenian Sea within the upper 70 meters of sediment. These deposits are hypothesized to have been triggered by explosive volcanic eruptions of the Campanian Volcanic Province, including the ~39.8 ka Campanian Ignimbrite (CI) super-eruption, which is among the largest known eruptions, having a volcanic explosivity index (VEI) of 7. These megabeds were intersected by Ocean Drilling Program (ODP) Leg 107 Site 650, where sediment cores were collected in 1986. However, their presence was not recognized at the time due to lack of appropriate geophysical data. To better understand the properties and origins of the Marsili Megabeds, we identified the megabeds within the ODP cores and conducted detailed sedimentological and elemental analyses, along with age dating, to determine their possible sediment provenance, depositional mechanisms, and potential triggering events. Elemental analysis and age dating suggest a potential link between these megabeds and known eruptions from the Campanian Volcanic Province, including the Neapolitan Yellow Tuffs eruption (14.9 ka), the Masseria del Monte Tuff eruption (29.3 ka), and the Campanian Ignimbrite super-eruption (39.8 ka). A new megabed discovered below the Y-7 tephra is older than 60,300 years but its triggering event is unknown. The re-examination of ODP cores reveals that not all megabeds conform to a megaturbidite morphology. In the Marsili Basin, the variety of sedimentological structures differs within and between megabeds, suggesting varying and complex depositional mechanisms. The findings reveal that the megabeds are more internally complex than previously thought, with variations in their depositional processes even in one basin.
How to cite: Sawyer, D., Higgins, F., and Urgeles, R.: Volcanic Triggers and Depositional Complexity of Submarine Megabeds in the Marsili Basin, Tyrrhenian Sea , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13362, https://doi.org/10.5194/egusphere-egu26-13362, 2026.
High-latitude continental margins host some of the largest submarine landslide worldwide. Much speculation has focused on their relationship to glaciomarine sedimentation, gas hydrates and seismic shaking and, ultimately, the climatic variations that link to the former three factors. In this study we aim to better understand the causal mechanisms of such events in high-latitude margins. We focus on the Antarctic continental margins, particularly the Pacific Margin of the Antarctic Peninsula, which have been less studied than its Arctic counterparts. We use a combined dataset of archive and recently acquired swath bathymetry and seismic data. Two distinct submarine landslide groups are identified according to the water depth they show up. The shallowest cluster has mode depth centered around 1500 mwd, while the deepest cluster mode depth is centered around 4500 mwd. Most of their source areas are in 15-20 º slopes and, opposed to the Arctic counterparts, exhibit relatively small magnitudes, ranging from 0.1 to 10 km2 in areal extent and between 0.1 to 1 km3 in volume. The identified submarine landslides are mainly located in tectonically active environments. In addition to glaciomarine sedimentation, both tectonics and gas hydrates, may act as triggering mechanisms for submarine landslides in the Antarctic Peninsula margin. Few landslides occur in gas hydrate bearing sediments, as evidenced by the occurrence of a BSR, and there is no evidence of submarine landslides rooted at the base of the gas hydrate stability zone. Approximately one half of the landslides occur along the area dominated by the glaciomarine sedimentary wedge, but the location of the deepest landslide cluster lays outside this wedge. Overall, high-exponents of a power-law fit to the frequency-magnitude relationship and fault-landslide neighborhood relationships suggest a potential seismic control on submarine landslide occurrence.
How to cite: Urgeles, R., Roldan, I., León, R., Pérez, L. F., Bartolomé, R., Estrada, F., and Llorente, M.: Submarine landslides of the Antarctic Peninsula accretionary wedge: competing effects of tectonics, gas hydrates and glaciomarine sedimentation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19108, https://doi.org/10.5194/egusphere-egu26-19108, 2026.
