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Location of main features in study area offshore from northwest Africa.a, The Agadir canyon (stippled), Agadir basin, Seine and Madeira abyssal plains; channel network between Agadir basin and Madeira abyssal plain (grey shade); Canary debris flow (CDF; shaded brown); debris avalanches (DA) from Canary Islands1, 2, 3, 4, 5, 6, 7. The path of the flow that deposited bed 5 is shown by arrows. Box indicates area shown in c. Bathymetric contours spaced at 500 m intervals. b, Change in seafloor gradient (red line) plotted against distance along flow path. c, Location of cores (filled circles), debris-flow deposit (debrite), and the location of the cross-sections shown in (28–48) and in Supplementary Figs 4 and 5 (the three bold black lines) in Agadir basin.
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Submarine landslides can generate sediment-laden flows whose scale is impressive. Individual flow deposits have been mapped that extend for 1,500 km offshore from northwest Africa. These are the longest run-out sediment density flow deposits yet documented on Earth. This contribution analyses one of these deposits, which contains ten times the mass...
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... flow deposits were correlated between cores using sand-fraction com- position, the ratio of coccolith species within mud, magnetic susceptibility, colour, thickness, and relative position of layers within the core 3,6 (for example, Supplementary Fig. 1). Ratios of coccolith nannofossil species within hemipela- gic mud were used to date the flows 2-6 , together with an oxygen isotope stra- tigraphy. ...
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Much remains to understand the dynamic processes during the flow of submarine landslides. A first relevant problem is to explain
the extraordinary mobility of submarine landslides, which has no comparison in subaerial mass movement. Another challenging
question is the apparent disparity between submarine landslides that remain compact for hundreds...
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... Documented turbidity currents can reach 19 m/s (e.g., Piper et al., 1999) and run out for hundreds to thousands of kilometres along submarine canyons (Talling et al., 2007), posing a potential threat to expensive seafloor infrastructures (Barley, 1999). As summarized by Clare et al. (2015) linear seabed infrastructures such as cables, umbilicals and pipelines are most vulnerable to transverse or oblique flow impacts typically expected at canyon crossings which may lead to drag, loss of in-place stability, undermining due to scour, or rupture. ...
Recent advances in direct monitoring of submarine canyons activity suggest that metocean events can prime or ultimately trigger turbidity currents at sub-annual to centennial frequencies, challenging the para-digm that such highly destructive flows typically result from infrequent submarine landslides. Here we present a methodology aimed to link information on nearshore circulation and sediment resuspension events such as floods, tides and storms to the downslope evolution of turbidity flows, applied to cyclone-triggered turbidity currents affecting a deep-sea gas development offshore northern Mozambique. We evaluate seabed current velocities at the canyon heads derived from a 10,000 year long synthetic cyclone database consistent with ex-pected future climate conditions. We couple the results for each event to a dedicated 1D turbidity current nu-merical model accounting for multiple grain-sizes, water entrainment and detrainment, overspill and spatial variations of the channel width and seabed gradient. The 1000’s of individual modelled events allow a statisti-cally consistent estimation of the return period of turbidity currents at different control points along the canyons, and provide an estimation of flow structure, density and velocity necessary to evaluate the risk for offshore developments. Results are validated by the analysis of core samples, seabed morphology and dedicated 3D modelling of critical events.
... Submarine landslides are an important criterion for assessing the stability of submarine engineering or island-and-reef systems (Hampton et al., 1996;Shipp et al., 2004;Talling et al., 2007;Carter et al., 2014). Submarine landslides are unconsolidated soft sediments on the seafloor, occurring downward along the weak structural surfaces under the action of gravity (Tripsanas et al., 2008;Rodríguez-Ochoa et al., 2015). ...
Landslides frequently block rivers, forming a barrier lake, resulting in a dam break event in the terrestrial environment. However, reports about the submarine landslides are scarce. Herein, the periplatform submarine landslides changing transport pathways of deepwater gravity flows within the southeastern region out of Xuande Atoll on the Xisha Islands, South China Sea, are described. Submarine landslides, including SL I and SL II, with a total area of 170.9 km 2 , were identified using up-to-date geophysical data, including multi-beam bathymetric and seismic data and sediment gravity cores. SL I directly connects the Sansha Canyon forming a large-scale negative relief with an area of 151.8 km 2 , developing the terraces, and transporting blocks and remnant blocks. SL II covers an area of 19.1 km 2 and was mainly deposited on the deepwater plain with a toe part that is higher than the initial seafloor. The negative relief created by SL I on the seafloor forms the dominant pathways for the gravity flows, creating the new active channel system directly flowing into the canyon. The turbidity currents flowing along the steep lateral margin of SL II formed the cyclic steps. The remnant submarine landslide deposits on the western canyon margin indicate that SL I previously blocked the canyon and formed a submarine barrier lake, which was then eroded by the gravity flows flowing along with the channel system within SL I and the upstream canyon. Finally, the canyon was formed again, whose axis was "pushed" eastward by SL I. These observations update the evolution model of submarine landslide on a carbonate platform slope and the transport system from the slope to the submarine canyon or the deep basin and clarify the stability of submarine engineering and island-and-reef systems.
... Submarine landslides are a major source of seafloor deformation and hazardous tsunamis, being capable of damaging both subaqueous and coastal infrastructures in single or multiple events Talling et al., 2007;Sun et al., 2018a). Previous research concerning slope instability processes usually separates major and long-term precondition factors such as high sediment supply, overpressure, and slope oversteepening, from short-term triggers that include earthquakes, volcanism, and human activity (Leynaud et al., 2009;Urlaub and Hjelstuen, 2020). ...
Submarine landslides are significant geohazards, capable of displacing large volumes of sediment from continental margins to deposit mass transport complexes (MTCs) and generate offshore tsunamis. However, the reactivation of MTCs after their initial failure has long been overlooked. By analyzing high-quality three-dimensional seismic reflection data and seismic attribute maps, as well as comparing the geometry of different MTCs, we investigate the development of long-term slope instability and its hazardous consequences on the northwest flank of the Storegga Slide on the Norwegian margin. Our results demonstrate that the reactivation of MTCs can deform both their inner structure and overlying strata, promoting the formation of sinuous channels and local slope failures on the seafloor. These findings further reveal the MTCs that are underconsolidated or comprise slide blocks may remain unstable for a long time after their initial failure, particularly when affected by slope undercutting and a corresponding reduction in lateral support. This study shows that MTC-prone sequences are more likely to comprise regions of continental slopes with long-term instability and recurring marine geohazards.
... Erosion at the base of the dense layer is balanced by sediment deposition or transfer into a trailing dilute sediment cloud, leading to near-uniform speeds (Fig. 7e). However, this model might not be applicable for turbidity currents in unconfined settings, such as basin plains, where very long (up to 2,000 km) runouts on low gradients (0.05°) can occur without substantial seabed erosion 86,88 . In such settings, slow-settling cohesive mud could provide the main driving force for the flow. ...
... On the other hand, the deposit may be distributed over large areas by highly mobile sediment ows (P. J. Talling et al., 2007), which can escape the resolution of mapping and imaging systems. Here, we focus particularly on the initial failed volume of a landslide as it is one of the key input parameters for tsunami models (e.g., Iglesias et al., 2012;Murty, 2003). ...
Submarine landslides pose major geohazards as they can destroy seafloor infrastructure such as communication cables and cause tsunamis. The volume of material displaced with the landslide is one factor that determines its hazard and is typically estimated using bathymetric and/or seismic datasets. Here, we review methods to determine the initial failed volume based on a well-constrained case study, the Ana Slide, a small slope failure in the Eivissa Channel off the eastern Iberian Peninsula. We find that not only the availability and quality of datasets but also the emplacement mechanism determines the quality of the volume estimation. In general, the volume estimation based on comparison of modern and reconstructed pre-failure seafloor topographies yields conservative, yet robust volumes for the amount of material that was mobilized. In contrast, volume estimated from seismic data may be prone to overestimation if no detailed constraints on the nature of the chaotic, transparent, or disrupted seismic facies commonly used to identify landslide material are available.
... The petrological characteristics of the gravity flow analysis show an important vertical association among the gravity flow deposits, indicating the successive evolution of gravity flows. These four vertical combinations are spatiotemporally interrelated and represent different processes of a deep-water sedimentary system, the vertical relationships of the different sedimentary types reflecting the conversion of fluid properties (Schwab et al., 1996;Mohrig et al., 1998;Talling et al., 2007;Sumner et al., 2009;Bernhardt et al., 2012). ...
Deep‐water gravity depositional processes and evolution in arc systems have become hot research topics in recent years. This study discusses the co‐evolution of volcanism and deep‐water gravity flow deposits at the southern margin of the Junggar Basin based on petrology, geochronology, and geochemistry analyses. The results showed that a massive collapse of unstable sediments from the slope was triggered by volcanism, resulting in the formation of slumping gravity flows. The occurrence of volcanic beds in the slump deposits confirmed that synchronous volcanism likely affected sediment instability and triggered gravity flows. The Th/Yb, Ta/Yb, and Th/Ta elemental ratios, U‐Pb ages of detrital zircons, and palaeocurrent directions indicated that the North Tianshan (NTS) island arc represented the provenance of the Qianxia Formation. Moreover, statistical data on the pyroclastic components in the gravity flow deposits revealed an intensity index of volcanism, which indicated that volcanism is strongly related to gravity flow deposits, especially in terms of the type and distribution of deposits. A model for volcanically triggered deep‐water gravity flow deposits was established to provide a more in‐depth understanding of the co‐evolution of volcanism and gravity flow deposits and depositional setting of the Late Palaeozoic NTS oceanic subduction margin in the Junggar Basin.
... The TJT1 anomaly should have originated at a depth deeper than GJT3. Turbidity currents can be also induced by seafloor landslides which are often caused by strong seismic ground motion (e.g., Talling et al. 2007;Shanmugam 2015). If both distinct landslide and associated turbidity current had immediately occurred within 3.5 h after the mainshock on a slope between TJT1 and GJT3, the onset of the TJT1 anomaly might have been possibly explained. ...
We investigated temperature records associated with seafloor pressure observations at eight stations that experienced the 2011 M w 9 Tohoku earthquake near its epicenter. The temperature data were based on the temperature measured inside the pressure transducer. We proposed a method to estimate ambient water temperature from the internal temperature using an equation of heat conduction. The estimated seafloor water temperature showed remarkable anomalies, especially increases several hours after the M w 9 earthquake. A station of P03 (sea depth of 1.1 km) showed an abrupt temperature increase of + 0.19 °C that occurred ~ 3 h after the earthquake, which lasted for several hours. At stations of GJT3 (sea depth of 3.3 km) and TJT1 (sea depth of 5.8 km), there were abrupt temperature anomalies of + 0.20 °C and + 0.10 °C that began to occur 3–4 h after the earthquake. These anomalies both decayed to their original levels over a few tens of days. During the decay processes, only TJT1 showed several intermittent temperature rises. A water temperature anomaly within + 0.03 °C was found up to ~ 500 m above TJT1 2 weeks after the earthquake. There was no significant anomaly at the other five stations. Processes to cause these seafloor temperature anomalies were discussed. The temperature anomaly of P03 was reasonably caused by a tsunami-generated turbidity current, as also suggested by a previous study. Meanwhile, we proposed a scenario that the abrupt temperature anomalies of GJT3/TJT1 and the intermittent anomalies of TJT1 were caused by warm water discharges from the subseafloor. The pathways of the warm water were probably composed of the branch normal fault between GJT3 and TJT1, the reverse fault near TJT1, the backstop interface, and perhaps reverse faults at the frontal prism. The proposed scenario was almost compatible with other studies based on epicentral observations. We estimated the heat properties of the initial temperature anomalies of GJT3/TJT1. The estimated heat source might be explained by that most of the geothermal fluids trapped in those fault pathways were discharged to the seafloor immediately after the earthquake. The onsets of the subsequent intermittent anomalies of TJT1 were possibly activated by low or falling ocean tidal loading.
... These findings suggest that gravity flows undergo flow transformation within C2. We interpret that the low seafloor gradient, presence of seafloor relief (up to 80 mhigh) along the channel floor and absence of confinement decelerate gravity flows entering C2, especially those that continue down C2-4 (cf., Talling et al., 2007;Wynn et al., 2012;Gavey et al., 2017). This flow deceleration results in deposition from the flow and consequent flow transformation either from a debris flow or higher density turbidity currents into more dilute turbidity currents (cf., Damuth, 1975Damuth, , 1980Talling et al., 2007). ...
... We interpret that the low seafloor gradient, presence of seafloor relief (up to 80 mhigh) along the channel floor and absence of confinement decelerate gravity flows entering C2, especially those that continue down C2-4 (cf., Talling et al., 2007;Wynn et al., 2012;Gavey et al., 2017). This flow deceleration results in deposition from the flow and consequent flow transformation either from a debris flow or higher density turbidity currents into more dilute turbidity currents (cf., Damuth, 1975Damuth, , 1980Talling et al., 2007). Sediment waves (Facies F) along C2-4 with a downslope decrease in dimension are thus interpreted as turbidite sediment waves (Fig. 14) (cf., Rebesco et al., 2021). ...
... The high remaining momentum can maintain a long extension of the landslides away from the slope and result in a great impact on submarine infrastructure. For instance, an impressive run-out up to 1500 km of submarine landslides together with generated turbidity currents has been reported (Talling et al. 2007;Azpiroz-Zabala et al. 2017). Therefore, other than the tsunami usually concerned, it is also critical to resolve the momentum variation of submarine landslides off the slope for the laying, protection and safety of submarine infrastructure. ...
... Most of the existing studies on submarine landslides mainly pay attention to the properties of the generated tsunami (Watts et al. 2003;Harbitz et al. 2006; Yavari-Ramshe & Ataie-Ashtiani 2016; Takabatake et al. 2020). A few investigated the characteristics of the deformable slide body but concentrated on the evolution of the slide shape (Shi et al. 2016;Grilli et al. 2017;Rauter 2021), the propagation velocity Tajnesaie, Shakibaeinia & Hosseini 2018;Pilvar, Pouraghniaei & Shakibaeinia 2019) or the run-out and the final deposit of the slides (Talling et al. 2007;Elverhoi et al. 2010;Parez & Aharonov 2015). The few papers on the momentum or energy of deformable submarine landslides (Watts et al. 2003;Ataie-Ashtiani & Najafi-Jilani 2008;López-Venegas et al. 2015;Clous & Abadie 2019; Yavari-Ramshe & Ataie-Ashtiani 2019; Cabrera et al. 2020) were exclusively devoted to the estimation of the generated waves, focusing on the momentum/energy transfer in the wave generation stage. ...
It has been reported that, in submarine landslides down a slope, only a small part of the landslide momentum was transferred to the tsunami while most was lost in the further propagation over the flat bed. The high momentum of landslides off a slope meant a long run-out and a great impact on underwater infrastructure. Nevertheless, little attention has been paid to the variation of momentum of deformable submarine landslides off a slope, i.e., the loss of momentum when the slides flow away from the slope over a flat bottom. In this paper, the translational momentum of deformable submarine granular landslides running down a non-erodible inclined bed is investigated with a two-phase Smoothed Particle Hydrodynamics (SPH) model. After flowing down the slope, the transport rate and flux of the landslide translational momentum along the propagation over the flat bottom are examined. The effects of physical variables of the slide, particularly the grain size, the initial compaction, and the front intrusion angle, on the variation of the translational momentum are explored. Accordingly, scaling relations of the spatial-temporal maximum transport rate and flux of the landslide translational momentum, as well as those of the slide final run-out and the generated leading wave height, are proposed. These scaling relations, though based on numerical data of small-scale granular landslides, demonstrate a preliminary attempt to develop practical expressions in the framework of momentum for estimating the run-out of real submarine landslides and the impact on underwater infrastructure.
... Figure 1 shows a schematic diagram of a typical submarine debris flow transport process and potential infrastructure at risk. The entire process can be described using three main regions [1,8,16,23,32,34]. Near the continental shelves, slope failure occurs as a block of soil that slides downslope. ...
... Field evidence suggests that some prototype flows contain substantial coarse grain content [27], which means they have low N por because of strong granular interactions. Meanwhile, fines-rich prototype flows [4,8,30,32] have high N por , which means that excess pore fluid pressure has shorter timescales for dissipation than accumulation because the interstitial fluid attenuates granular interactions [17]. However, model flows usually adopt fine sand as the debris mixture instead of coarse grains observed in some prototype flows [27,34]. ...
... In contrast, turbidite mainly consisted of pelagic and hemipelagic fines. Moreover, the deposits at Offshore Northwest Africa and the slide at Mississippi Fan [32][33][34] reported the large granules in the debrite at locations further upstream of the flow path. In contrast, fines rich turbidite was observed in the more distal limits of the flow path. ...
Submarine debris flows are among the largest mass movements on planet earth. Over recent decades, scientists have modelled submarine debris flows in laboratory settings. However, little attention has been paid to scaling, which is central to understanding the potential limitations of laboratory experiments in modelling field-scale events. Existing scaling principles generally treat complex submarine soil–water mixtures as an equivalent fluid. Although this approach is practical, it may overlook the potential importance of granular and grain-fluid interactions, which affect the pore pressure feedback mechanisms that regulate the macroscopic flow dynamics. In this study, a systematic review of laboratory and field data of submarine debris flows in the literature is carried out from a mesoscopic point-of-view. Results reveal that collisional and frictional grain interactions of field flows play a more important role in the dynamics than those represented by laboratory experiments, which are generally modelled as viscous suspensions with finer particle sizes. Furthermore, existing laboratory flows appear to disproportionately represent frictional stresses at the flow-bed interface, which has the effect of reducing the role played by seabed erosion and the generation of excess pore pressure at the flow-bed interface to facilitate hydroplaning.
