Anders Elverhøi

• De Blasio, Fabio V; Breien, Hedda & Elverhøi, Anders (2011). Modelling a cohesive-frictional debris flow: an experimental, theoretical, and field-based study. Earth Surface Processes and Landforms.  ISSN 0197-9337.  36(6), s 753- 766 . doi: 10.1002/esp.2101 Show summary

  The rheology of debris flows is difficult to characterize owing to the varied composition and to the uneven distribution of the components that may range from clay to large boulders, in addition to water. Few studies have addressed debris flow rheology from observational, experimental, and theoretical viewpoints in conjunction. We present a coupled rheological-numerical model to characterize the debris flows in which cohesive and frictional materials are both present. As a first step, we consider small-scale artificial debris flows in a flume with variable percentages of clay versus sand, and measure separately the rheological properties of sand–clay mixtures. A comparison with the predictions of a modified version of the numerical model BING shows a reasonable agreement between measurements and simulations. As application to a field case, we analyse a recent debris flow that occurred in Fjærland (Western Norway) for which much information is now available. The event was caused by a glacial lake outburst flood (GLOF) originating from the failure of a moraine ridge. In a previous contribution (Breien et al., Landslides, 2008, 5: 271–280) we focused on the hydrological and geomorphological aspects. In particular we documented the marked erosion and reported the change in sediment transport during the event. In contrast to the laboratory debris flows, the presence of large boulders and the higher normal pressure inside the natural debris flow requires the introduction of a novel rheological model that distinguishes between mud-to–clast supported material. We present simulations with a modified BING model with the new cohesive-frictional rheology. To account for the severe erosion operated by the debris flow on the colluvial deposits of Fjærland, we also suggest a simple model for erosion and bulking along the slope path. Numerical simulations suggest that a self-sustaining mechanism could partly explain the extreme growth of debris flows running on a soft terrain

• De Blasio, Fabio V & Elverhøi, Anders (2011). Properties of mass-transport deposits as inferred from dynamic modeling of subaqueous mass wasting: a short review. Special Publication - Society for Sedimentary Geology.  ISSN 1060-071X.  96, s 499- 508
• Vanneste, Maarten; Harbitz, Carl Bonnevie; De Blasio, Fabio V; Glimsdal, Sylfest; Mienert, Jurgen & Elverhøi, Anders (2011). Hinlopen-Yermak landslide, Arctic ocean-geomorphology, landslide dynamics, and tsunami simulations. Special Publication - Society for Sedimentary Geology.  ISSN 1060-071X.  96, s 509- 527
• Breien, Hedda; De Blasio, Fabio V; Elverhøi, Anders; Nystuen, Johan Petter & Harbitz, Carl Bonnevie (2010). Transport mechanisms of sand in deep-marine environments-insights based on laboratory experiments. Journal of Sedimentary Research.  ISSN 1527-1404.  80(11), s 975- 990 . doi: 10.2110/jsr.2010.079
• De Blasio, Fabio V; Breien, Hedda & Elverhøi, Anders (2010). Modelling a cohesive-frictional debris flow: an experimental, theoretical, and field-based study. Earth Surface Processes and Landforms.  ISSN 0197-9337. . doi: 10.1002/esp.2101
• Elverhøi, Anders; Breien, Hedda; De Blasio, Fabio V; Harbitz, Carl Bonnevie & Pagliardi, M. (2010). Submarine landslides and the importance of the initial sediment composition for run-out length and final deposit. Ocean Dynamics.  ISSN 1616-7341.  60(4), s 1027- 1046 . doi: 10.1007/s10236-010-0317-z Full text in Research Archive. Show summary

  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 of kilometres and those that disintegrate during the flow, finally evolving into turbidity currents. This problem is linked to a central ongoing debate on the relative importance of turbidity currents versus submarine landslides in reshaping the continental margin. Based on three epitomic case studies and on laboratory experiments with artificial debris flows of various composition, we suggest a possible explanation for the disparity between compact and disintegrating landslides, identifying the clay-to-sand ratio as the key control parameter.

• Breien, Hedda; De Blasio, Fabio V; Elverhøi, Anders & Høeg, Kaare (2008). Erosion and morphology of a debris flow caused by a glacial lake outburst flood, Western Norway. Landslides. Journal of the International Consortium on Landslides.  ISSN 1612-510X.  5, s 271- 280 . doi: 10.1007/s10346-008-0118-3
• De Blasio, Fabio V & Elverhøi, Anders (2008). A model for frictional melt production beneath large rock avalanches. Journal of Geophysical Research.  ISSN 0148-0227.  113 . doi: 10.1029/2007JF000867
• Vanneste, Maarten; Harbitz, C.; De Blasio, Fabio V.; Glimsdal, Sylfest; Mienert, Jurgen & Elverhøi, Anders (2008). Mass-transport deposits from the Hinlopen Slide, Arctic Ocean - their geomorphology, slide dynamics and tsunami potential. Sedimentary Geology.  ISSN 0037-0738.
• Breien, Hedda; Pagliardi, M.; De Blasio, Fabio V; Issler, Dieter & Elverhøi, Anders (2007). Experimental studies of subaqueous vs. subaerial debris flows - velocity characteristics as a function of the ambient fluid, In Vasilios Lykousis; Dimitris Sakellariou & Jacques Locat (ed.),  Submarine mass movements and their consequences. 3rd International Symposium.  Springer.  ISBN 9781402065118.  Section 2.  s 101 - 110
• De Blasio, Fabio Vittorio; Elverhøi, Anders; Engvik, Lars; Issler, Dieter; Gauer, Peter & Harbitz, Carl Bonnevie (2006). Understanding the high mobility of subaqueous debris flows. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  86, s 10 Show summary

  Submarine mass wasting in the form of glacial mudflows, river-laden debris flows, rock avalanches, sandy debris flows, outrunner blocks, or turbidity currents, reveal an extraordinary mobility, demonstrated by the very long runout distance between the source area and the final deposit, even on very gentle gradients. Laboratory experiments reveal that the dynamical behaviour of artificial debris flows depends dramatically on the claysand ratio in the experimental slurry. Artificial debris flows with high clay content, which are possibly a realistic replica of mudflows in glaciallyinfluenced areas, tend to form a thin water layer underneath the head which acts as a natural lubricant. In contrast, lubrication cannot be easily invoked for sand-rich gravity flows. Experiments show that sandy debris flows lack cohesion, and that sand settles quickly during the rapid disaggregating phase. In the present work we review the field data, experimental results gained with debris flows of various compositions, and the status of theoretical studies and numerical simulations of submarine debris flows. When dealing with debris flows that remain compact, such as clay-rich debris flows and outrunner blocks, both experiments and simulations indicate the importance of water lubrication for mobility. On the other hand, sandy debris flows are far more complicated owing to the increased importance of water penetration, disintegration, and turbulence, and these difficulties are reflected in greater intricacy of experiments and computer simulations. Thus, the problem of whether sandy debris flows may be highly mobile in the natural setting still remains elusive.

• De Blasio, Fabio V; Elverhøi, Anders; Engvik, Lars E.; Issler, Dieter; Gauer, Peter & Harbitz, Carl Bonnevie (2006). Understanding the high mobility of subaqueous debris flows. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  86(3), s 275- 284
• de Blasio, Fabio V; Engvik, LE & Elverhøi, Anders (2006). Sliding of outrunner blocks from submarine landslides. Geophysical Research Letters.  ISSN 0094-8276.  33(L06614)
• De Blasio, Fabio Vittorio; Engvik, Lars & Elverhøi, Anders (2006). Sliding of outrunner blocks from submarine landslides. Geophysical Research Letters.  ISSN 0094-8276.  33(L06614) Show summary

  Outrunner blocks are nearly intact pieces of debris that detach from a slowing-down submarine landslide and flow ahead of the front. Data gathered from different sliding areas highlight some properties of outrunner blocks and in particular their inordinate mobility reflected in runouts of up to 25 kilometres, even on very gentle slopes. Blocks may produce an erosion glide track on the sea floor few centimetres to several metres deep, which in some cases exhibits regularly spaced grooves along the flow direction. Understanding the dynamics of outrunner blocks may shed light on the flow and lubrication of submarine landslides. We develop a simple hydrodynamic model of a rigid block interacting with ambient water and subject to lubrication with the sea floor, and calculate numerically the equation of motion for the block. We find that as a consequence of lift forces and water lubrication, the block may reach long runouts, in agreement with data. When the block is moving at high speed, we find an oscillating solution to the equations of motion which could explain the creation of dashed grooves.

• Engvik, Lars; De Blasio, Fabio V & Elverhøi, Anders (2006). Small scale simulations of outrunner blocks. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  86(3), s 301- 307
• Engvik, Lars; De Blasio, Fabio Vittorio & Elverhøi, Anders (2006). Small scale simulations of outrunner blocks. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  86, s 7 Show summary

  Submarine debris flows are often accompanied by isolated blocks located some distance beyond the rest of the failed mass. These so-called outrunner blocks have the ability to travel over long distances on very gentle slopes. Glide tracks of various depths are observed in some cases, while in others no traces of significant erosion can be detected, which indicates that outrunner blocks are able to travel completely separated from the bed. Similar phenomena occur in laboratory experiments, where chunks detach from the front of a small-scale debris flow and move out ahead of the rest of the flow.We present a two-dimensional, small-scale model of a rigid block subjected to gravity combined with the complete dynamical interaction with the surrounding liquid. Our simulations indicate that the block is able to hydroplane completely separated from the bed and attain long runout distances. The maximum velocity of the block is close correlated with the thickness of the block. For the simple shape assumed in our model we find that the densimetric Froude number is ?0.8 . Depending on the geometrical shape of the block, size and the slope angle, we observe oscillatory motion, where the front of the block is lifted periodically and the rear part tends to scrape the bed. The pressure distribution around the block indicates that the block is likely to deform at the rear end as well as the front.

• Gauer, Peter; Elverhøi, Anders; Issler, Dieter & De Blasio, Fabio V (2006). On numerical simulations of subaqueous slides: Back-calculations of laboratory experiments of clay-rich slides. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  86(3), s 295- 300
• Elverhøi, Anders; Issler, Dieter; de, Blasio Fabio V; Ilstad, Trygve; Harbitz B, Carl & Gauer, Peter (2005). Emerging insights into the dynamics of submarine debris flows. Natural hazards and earth system sciences.  ISSN 1561-8633.  5, s 633- 648 Show summary

  Recent experimental and theoretical work on the dynamics of submarine debris flows is summarized. Hydroplaning was first discovered in laboratory flows and later shown to likely occur in natural debris flows as well. It is a prime mechanism for explaining the extremely long runout distances observed in some natural debris flows even of over-consolidated clay materials. Moreover, the accelerations and high velocities reached by the flow head in a short time appear to fit well with the required initial conditions of observed tsunamis as obtained from back-calculations. Investigations of high-speed video recordings of laboratory debris flows were combined with measurements of total and pore pressure. The results are pointing towards yet another important role of ambient water: Water that intrudes from the water cushion underneath the hydroplaning head and through cracks in the upper surface of the debris flow may drastically soften initially stiff clayey material in the "neck" of the flow, where significant stretching occurs due to the reduced friction at the bottom of the hydroplaning head. This self-reinforcing process may lead to the head separating from the main body and becoming an "outrunner" block as clearly observed in several natural debris flows. Comparison of laboratory flows with different material composition indicates a gradual transition from hydroplaning plug flows of stiff clay-rich material, with a very low suspension rate, to the strongly agitated flow of sandy materials that develop a pronounced turbidity current. Statistical analysis of the great number of distinguishable lobes in the Storegga slide complex reveals power-law scaling behavior of the runout distance with the release mass over many orders of magnitude. Mathematical flow models based on viscoplastic material behavior (e.g. BING) successfully reproduce the observed scaling behavior only for relatively small clay-rich debris flows while granular (frictional) models fail at all scales. For very large release masses, hydroplaning or significant softening of the shear layer due to water incorporation must be invoked to recover the observed scaling behavior; a combination of both effects likely will give the most realistic description of the phenomenon. Detailed studies of the neck behavior and the compositional dependence of the material properties are needed to arrive at a quantitative model. Other related and important open questions concern the rheological model appropriate for sandy debris flows and the suspension rate from the dense body into the associated turbidity current.

• Landvik, J.; Ingólfsson, Ólafur; Ingolfsson, O.; Mienert, Jurgen; Lehman, Scott J.; Solheim, A.; Elverhøi, Anders & Ottesen, D. (2005). Rethinking Late Weichselian ice sheet dynamics in coastal NW Svalbard. Boreas.  ISSN 0300-9483.  34(1), s 1- 19 . doi: 10.1080/03009480510012809
• Lastras, Galderic; de, Blasio Fabio V; Canals, Miquel & Elverhøi, Anders (2005). CONCEPTUAL AND NUMERICAL MODELING OF THE BIG’95 DEBRIS FLOW, WESTERN MEDITERRANEAN SEA. Journal of Sedimentary Research.  ISSN 1527-1404.  75, s 784- 797 . doi: 10.2110/jsr.2005.063
• de, Blasio Fabio V; Elverhøi, Anders; Issler, Dieter; Harbitz B, Carl; Bryn, Petter & Lien, Reidar (2005). On the dynamics of subaqueous clay rich gravity mass flows—the giant Storegga slide, Norway. Marine and Petroleum Geology.  ISSN 0264-8172.  22, s 179- 186
• Issler, Dieter; Elverhøi, Anders; de, Blasio Fabio V; Bryn, Petter & Lien, Reidar (2005). Scaling behaviour of clay-rich submarine debris flows. Marine and Petroleum Geology.  ISSN 0264-8172.  22, s 187- 194
• Landvik, Jon Y.; Ingólfsson, Ólafur; Mienert, Jürgen; Lehman, Scott J.; Solheim, Anders; Elverhøi, Anders & Ottesen, Dag (2005). Rethinking Late Weichselian ice-sheet dynamics in coastal NW Svalbard. Boreas.  ISSN 0300-9483.  34, s 7- 24 Show summary

  New marine geological evidence provides a better understanding of ice-sheet dynamics along the western margin of the last Svalbard/Barents Sea Ice Sheet. A suite of glacial sediments in the Kongsfjordrenna cross-shelf trough can be traced southwards to the shelf west of Prins Karls Forland. A prominent moraine system on the shelf shows minimum Late Weichselian ice extent, indicating that glacial ice also covered the coastal lowlands of northwest Svalbard. Our results suggest that the cross-shelf trough was filled by a fast-flowing ice stream, with sharp boundaries to dynamically less active ice on the adjacent shelves and strandflats. The latter glacial mode favoured the preservation of older geological records adjacent to the main pathway of the Kongstforden glacial system. We suggest that the same model may apply to the Late Weichselian glacier drainage along other fjords of northwest Svalbard, as well as the western margin of the Barents Ice Sheet. Such differences in glacier regime may explain the apparent contradictions between the marine and land geological record, and may also serve as a model for glaciation dynamics in other fjord regions.

• Solheim, Anders; Bhasin, Rajinder; de, Blasio Fabio V; Blikra, Lars H.; Boyle, Stan; Braathen, Alvar; Dehls, John; Elverhøi, Anders; Etzelmuller, Bernd; Glimsdal, Sylfest; Harbitz, Carl Bonnevie; Heyerdahl, Håkon; Høydal, Øyvind Armand; Iwe, Harald; Karlsrud, Kjell; Lacasse, Suzanne; Lecomte, Isabelle; Lindholm, Conrad; Longva, Oddvar; Løvholt, Finn; Nadim, Farrokh; Nordal, Steinar; Romstad, Bård; Rød, Jan Ketil & Strout, James M. (2005). International Centre for Geohazards (ICG): Assessment, prevention and mitigation og geohazards. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  85(1&2), s 45- 62 Show summary

  There is an urgent need to improve the basic understanding of geohazards and our ability to deal with the risks associated with them. The International Centre for Geohazards (ICG) does research on the assessment, prevention and mitigation of geohazards, offshore as well as on land. The main focus is placed on landslides and their effects, such as tsunamis. Activities include hazard and risk assessment for slides and earthquakes, evaluation of soil and rock slopes, instrument design and monitoring, geophysical methods, field studies, application of SAR technology for monitoring of slopes, further development of GIS as a tool in geohazard assessment, tsunami research, and numerical modelling. Education is given high priority, and graduate programmes in geohazards have been established at both the University of Oslo and at NTNU in Trondheim. Over the next few years, emphasis will also be placed on monitoring, early warning systems, and mitigation measures.

• Ilstad, Trygve; Elverhøi, Anders; Issler, Dieter & Marr, Jeffrey G (2004). Subaqueous debris flow behaviour and its dependence on the sand/clay ratio: a laboratory study using particle tracking. Marine Geology.  ISSN 0025-3227.  213, s 415- 438
• De Blasio, F.V.; Ilstad, Trygve; Elverhøi, Anders; Issler, Dieter & Harbitz, Carl Bonnevie (2004). High Mobility Of Subaqueous Debris Flows And The Lubricating-Layer Model, In  OTC2004. Offshore Technology Conference, Innovation without limits, OTC04. Proceedings, 3-6 May, 2004, Reliant Center, Houston, Texas.  Offshore Technology Conference.  ISBN 978-1-55563-251-9.  16747-MS.
• De Blasio, Fabio Vittorio; Engvik, Lars; Elverhøi, Anders & Harbitz, Carl Bonnevie (2004). Hydroplaning and submarine debris flows. Journal of Geophysical Research.  ISSN 0148-0227.  109 Show summary

  Examination of submarine clastic deposits along the continental margins reveals the remnants of holocenic or older debris flows with run-out distances up to hundreds of kilometers. Laboratory experiments on subaqueous debris flows, where typically one tenth of a cubic meter of material is dropped down a flume, also show high velocities and long run-out distances compared to subaerial debris flows. Moreover, they show the tendency of the head of the flow to run out ahead of the rest of the body. The experiments reveal the possible clue to the mechanism of long run-out. This mechanism, called hydroplaning, begins as the dynamic pressure at the front of the debris flow becomes of the order of the pressure exerted by the weight of the sediment. In such conditions a layer of water can intrude under the sediment with a lubrication effect and a decrease in the resistance forces between the sediment and the seabed. A physical-mathematical model of hydroplaning is presented and investigated numerically. The model is applied toboth laboratory- and field-scale debris flows. Agreement with laboratory experiments makes us confident in the extrapolation of our model to natural flows and shows that long run-outdistances can be naturally attained.

• de, Blasio Fabio V; Elverhøi, Anders; Issler, Dieter; Harbitz, Carl Bonnevie; Bryn, Petter & Lien, Reidar (2004). Flow models of natural debris flows originating from overconsolidated clay materials. Marine Geology.  ISSN 0025-3227.  213, s 439- 455 Show summary

  In this paper, slides and debris flows in overconsolidated clay materials are simulated numerically. As a case study, the models are applied to the Storegga slide in the Norwegian Sea and in particular to the sub-region called Ormen Lange, where the information available is the most precise for a subaqueous debris flow. Three different models for the rheology of clay are used: a viscoplastic (Bingham) fluid model, a viscoplastic fluid with interspersed solid blocks, and a viscoplastic model with yield strength increasing with depth. The small-scale debris flows in the Ormen Lange area can be reasonably well understood in terms of a pure Bingham model without granular effects and blocks. The presence of intact blocks in the region, however, indicates that at least the top layer of the sliding sediments was not destroyed by the flow. It suggests that the flow occurred mainly at high shear rate in a lubricating layer of mud deriving partly from the disintegration of the block�s own material, and possibly from the entrainment of hemipelagic sediments along the flow path while the top part was left unsheared. The failure of the model with blocks probably stems from the use of the Coulomb friction law to represent the interaction between the block and the seabed. The Bingham model works better because during the flow of such fluids an unsheared plug region is formed naturally, even in unconsolidated materials. Combining the simulations with these three models, a possible scenario for the Ormen Lange debris flows is deduced according to which the lubricating layer supporting the blocks has a yield strength of about 10�15 kPa.

• de, Blasio Fabio V; Engvik, Lars; Harbitz, Carl Bonnevie & Elverhøi, Anders (2004). Hydroplaning and submarine debris flows. Journal of Geophysical Research.  ISSN 0148-0227.  109 . doi: 10.1029/2002JC001714,
• Ilstad, Trygve; De Blasio, Fabio Vittorio; Elverhøi, Anders; Harbitz, Carl Bonnevie; Engvik, Lars & Longva, Oddvar (2004). On the frontal dynamics and morphology of submarine debris flows. Marine Geology.  ISSN 0025-3227.  213(4), s 481- 497 Show summary

  Several submarine debris flows show an apparently chaoticfrontal part with blocks of variable size (from roughly tensto some hundreds of metres) located some distance beyond thefront of the main deposits. This outrunner phenomenon was studied both in the field and in laboratory experiments. Depositional patterns in a field case (Finneidfjord, northern Norway) are classified from the outer distal part of the debris flow to the outermost outrunner block. Similar patterns were found in experimental debris flows, and we suggest that flow processes in the laboratory are applicable to the field example. Theoretical investigations are applied to assess frontal dynamics and especially the formation and motion of outrunner blocks. As the front of the debris flow pushes through ambientwater, a combination of front pressure and lift force allowsfor intrusion of a water layer underneath the front (hydroplaning). This water layer reduces basal friction and induces tensile stresses farther behind the front, leading to a possible detachment and decoupling with respect to the main slide body. These outrunner blocks show an increased mobility compared to the main slide body and deposition of such blocks may occur far away from the main slide body.

• Ilstad, Trygve; de, Blasio Fabio V; Elverhøi, Anders; Harbitz, Carl Bonnevie; Engvik, Lars; Longva, Oddvar & Marr, Jeffrey G (2004). On the frontal dynamics and morphology of submarine debris flows. Marine Geology.  ISSN 0025-3227.  213, s 481- 497 Show summary

  Several submarine debris flows show an apparently chaotic frontal part with blocks of variable size (from roughly tens to some hundreds of metres) located some distance beyond the front of the main deposits. This outrunner phenomenon was studied both in the field and in laboratory experiments. Depositional patterns in a field case (Finneidfjord, northern Norway) are classified from the outer distal part of the debris flow to the outermost outrunner block. Similar patterns were found in experimental debris flows, and we suggest that flow processes in the laboratory are applicable to the field example. Theoretical investigations are applied to assess frontal dynamics and especially the formation and motion of outrunner blocks. As the front of the debris flow pushes through ambient water, a combination of front pressure and lift force allows for intrusion of a water layer underneath the front (hydroplaning). This water layer reduces basal friction and induces tensile stresses farther behind the front, leading to a possible detachment and decoupling with respect to the main slide body. These outrunner blocks show an increased mobility compared to the main slide body and deposition of such blocks may occur far away from the main slide body.

• Ilstad, Trygve; Marr, Jeffrey G; Elverhøi, Anders & Harbitz, Carl Bonnevie (2004). Laboratory studies of subaqueous debris flows by measurements of pore-fluid pressure and total stress. Marine Geology.  ISSN 0025-3227.  213, s 403- 414 Show summary

  A set of laboratory experiments on subaqueous debris flows is reported where total stress as well as pore pressure transducers were mounted in the bed. Sediment texture ranging from clayey (viscoplastic) to sandy (granular) were used in the experiments, in order to investigate changes in pressure evolution. The pressure readings confirm earlier studies suggesting that the front of the subaqueous clayey debris flow is hydroplaning on a thin layer of water, which causes low bed friction. Fronts of sandy debris flows show a fluidized head where bed friction is minimal.

• Issler, Dieter; Blasio, F. V. de; Elverhøi, Anders; Ilstad, Trygve; Haflidason, H; Bryn, P & Lien, R (2003). Issues in the assessment of gravity mass flow hazard in the Storegga area off the Western Norwegian coast. Kluwer Academic.  s 231- 238
• De Blasio, Fabio V; Issler, Dieter; Elverhøi, Anders; Harbitz, Carl Bonnevie; Ilstad, Trygve; Bryn, P; Lien, R & Løvholt, Finn (2003). Dynamics, Velocity and Run-Out of the Giant Storegga Slide, In Jacques Locat; Jürgen Mienert & Luc Boisvert (ed.),  Submarine mass movements and their consequences, 1st International Symposium.  Kluwer Academic Publishers.  ISBN 1-4020-1244-6.  Section 2 / Altantic Ocean.  s 223 - 230 Show summary

  A huge slide (volume of 2400 km3 and run-out 450 km) was released in the Storegga area off the western coast of Norway during early Holocene, followed by numerous smaller debris flows. We perform numerical simulations of the giant slide using a Bingham model for the clay material. Agreement with present deposit distribution and run-out is found by assuming that the shear resistance between the debris flow and the seabed decreases during the flow, and we suggest sediment remolding or hydroplaning as possible explanations. Debris velocities are predicted and possible applications to the associated tsunami event are investigated.

• Harbitz, Carl Bonnevie; Parker, Gary; Elverhøi, Anders; Marr, Jeffrey G; Mohrig, David & Harff, Peter A (2003). Hydroplaning of subaqueous debris flows and glide blocks: Analytical solutions and discussion. Journal of Geophysical Research.  ISSN 0148-0227.  108(B7) . doi: 10.1029/2001JB001454 Show summary

  Subaqueous debris flows often attain significantly higher velocities and longer run-out distances than their subaerial counterparts in spite of increased viscous drag and reduced effective gravity due to buoyancy. Recent experimental research suggests that a basal lubricating layer of water associated with hydroplaning decouples the sediments from the bed, resulting in a dramatic reduction of the basal shear stress. Hydroplaning thus provides an explanation for these observations. The conditions for onset of hydroplaning are discussed in terms of critical densimetric Froude number. The stress reduction due to a lubricating layer of water or mud slurry is studied via equilibrium solutions for a two-layer Couette flow. The calculations reveal that the stresses in both the low-viscosity lubricating layer and the high-viscosity deforming deposits below it are substantially reduced. The principles of laminar boundary layers are used to develop an equilibrium solution for the steady motion of a hydroplaning debris glide block. This adjusted version of lubrication theory properly accounts for hydroplaning associated with a dynamic pressure generated at the head of the block. Example calculations at both laboratory and field scale support the experimental results of reduced bed friction, limited erosion, sediment rheology independence, and high velocities. The results also reveal the possibility for a net up-slope discharge in the lubricating layer.

• Blasio, Fabio V. de; Issler, Dieter & Elverhøi, Anders (2002). Dynamics, velocity and run-out of the giant Storegga Slide. Kluwer Academic.
• Butt, Faisal Ahmed; Drange, H.; Elverhøi, Anders; Otterå, O.H. & Solheim, Anders (2002). Modelling late Cenozoic isostatic elevation changes in the Barents Sea and their implications for oceanic and climatic regimes: preliminary results. Quaternary Science Reviews.  ISSN 0277-3791.  21, s 1643- 1660
• Dowdeswell, Julian & Elverhøi, Anders (2002). The timing of initiation of fast-flowing ice streams during a glacial cycle inferred from glacimarine sedimentation. Marine Geology.  ISSN 0025-3227.  188, s 3- 14
• Elverhøi, Anders; De Blasio, Fabio Vittorio; Butt, Faisal Ahmed; Issler, Dieter; Harbitz, Carl Bonnevie; Engvik, Lars; Solheim, Anders & Marr, Jeff (2002). Submarine mass-wasting on glacially-influenced continental slopes: processes and dynamics. ?.  203, s 73- 87 . doi: 10.1144/​GSL.SP.2002.203.01.05 Show summary

  Submarine slides and debris flows are common and effective mechanisms of sediment transfer from the continental shelf to deeper parts of the basin. They are particularly common along glaciated margins that have experienced high sediment fluxes to the shelf break during and after glacial maxima. During one single event, typically lasting for a few hours or less, enormous sediment volumes can be transported over distances exceeding hundreds of kilometres, even on very gentle slopes. In order to understand the physics of these mass flows, one ideally divides the process into a release phase, followed by break-up, flow and final deposition. Little is presently known regarding the release and break-up, although some plausible explanations can be inferred from basic mechanics of granular materials. Once initiated, the flow of clay-rich or muddy sediments may be assumed to behave as a (non-Newtonian) Herschel-Bulkley fluid. Fluid dynamic concepts can then be applied to describe the flow provided the rheological properties of the material are known. Numerical modelling supports our assertion that the long runout distances observed for large volumes of sediments moving down gentle slopes can be explained by partial hydroplaning of the flowing mass. Hydroplaning might also explain the sharp decrease of the friction coefficient for submarine mass flows as a function of the released volume. The paper emphasises the need for a better understanding of the physics of mass wasting in the submarine environment.

• Marr, Jeffrey G; Elverhøi, Anders; Harbitz, Carl Bonnevie; Imran, Jasim & Harff, Peter A (2002). Numerical simulation of mud-rich subaqueous debris flows on the glacially active margins of the Svalbard-Barents Sea. Marine Geology.  ISSN 0025-3227.  188, s 351- 364 . doi: 10.1016/S0025-3227(02)00310-9 Show summary

  Seismic images and sediment core data from the Bear Island and Isfjorden fans localized along the Svalbard–Barents Sea continental margin, reveal an interesting depositional system consisting of stacked debris flow lobes. The frequent release of debris flows was associated with large volumes of sediment rapidly delivered to the shelf break during periods of maximum glaciation. The compositions of the lobes for both fans are similar, consisting of mainly clay and silt. The data show, however, a dramatic difference in runout distances for the two areas. Isfjorden debris lobes are 10–30 km in length whereas Bear Island lobes are 100–200 km in length. Even more intriguing is the fact that the large runout distances on the Bear Island fan occurred on slopes less than 1° whereas the Isfjorden fan flows occurred on slopes greater than 4°. Depth-averaged non-linear one-dimensional equations for balance of mass and linear momentum are applied to simulate the subaqueous debris flow. The equations are solved by the numerical model BING, describing the flow as a visco-plastic Bingham fluid. The model is employed to study the effect yield strength, viscosity and bathymetry have on debris flow runout. The study shows that the large runout distances can be achieved on the Bear Island fan by visco-plastic flows with sufficiently low yield strength. High yield strength sediments require an additional mechanism, such as hydroplaning, to reach measured runout distances. Most importantly, this study shows the necessity of good rheological measurements for accurate numerical modeling of subaqueous debris flows.

• Siegert, M.; Dowdeswell, Julian; Svennevig, Jan Ludvig & Elverhøi, Anders (2002). The Eurasian Arctic during the last ice age. American Scientist.  ISSN 0003-0996.  20, s 32- 39
• Butt, Faisal Ahmed; Elverhøi, Anders; Foirsberg, Carl Fredrik & Solheim, Anders (2001). Evolution of the Scoresby Sund fan, central east Greenland - evidence from ODP Site 987. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  81, s 3- 15
• Butt, Faisal Ahmed; Elverhøi, Anders; Forsberg, C.F. & Solheim, Anders (2001). Evolution of the Scoresby Sund Fan, central East Greenland - evidence from ODP Site 987. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  s 3- 15
• Butt, Faisal Ahmed; Elverhøi, Anders; Hjelstuen, B.O.; Dimakis, P. & Solheim, Anders (2001). Modelling late Cenozoic isostatic elevation changes in Storfjorden, NW Barents Sea: an indication of varying erosional regimes. Sedimentary Geology.  ISSN 0037-0738.  143, s 71- 89
• Elverhøi, Anders (2001). Holocene paleoclimate data from the Arctic: testing models of global climate change. Quaternary Science Reviews.  ISSN 0277-3791.  20, s 1275- 1287
• Dimakis, P.; Elverhøi, Anders; Høeg, Kaare; Solheim, Anders; Harbitz, Carl Bonnevie; Laberg, Jan Sverre; Vorren, Tore Ola & Marr, Jeff (2000). Submarine slope stability on high-latitude glaciated Svalbard–Barents Sea margin. Marine Geology.  ISSN 0025-3227.  162(2-4), s 303- 316 . doi: 10.1016/S0025-3227(99)00076-6 Show summary

  Slope stability is evaluated at two locations on high latitude, deep sea fans along the Svalbard–Barents Sea margin, based on available samples and using an “infinite slope” analysis. The stability evaluation uses the Mohr–Coulomb failure criterion, and a semi-analytical approach based on Gibson's formulation for determining the excess pore pressure build-up due to sedimentation. The main results are presented in the form of contour plots of slope safety factors in a diagram with axes of time and thickness of deposit. The results show that during rapid sedimentation, which mostly takes place during periods of maximum glaciation with the ice front located along the shelf edge, slope failure will occur with a frequency varying between 95 and 170 years. Only part of the upper sedimented layer will be mobilised (10–30 m), while the remaining thickness (40–70 m) will remain at the initial sedimentation site. These results may explain why the continental slope is characterised by relatively uniform sediment thickness from upper to lower slope.

• Elverhøi, Anders; Harbitz, Carl Bonnevie; Dimakis, P.; Mohrig, David; Marl, Jeff & Parker, Gary (2000). On the Dynamics of Subaqueous Debris Flows. Oceanography.  ISSN 1042-8275.  13(3), s 109- 117 . doi: 10.5670/oceanog.2000.20
• Dimakis, P.; Braathen, B.I.; Faleide, Jan Inge; Elverhøi, Anders & Gudlaugsson, Steinar Thor (1999). The Cenozoic uplift and erosion of the Svalbard-Barents Sea region. Tectonophysics.  ISSN 0040-1951.  300, s 311- 327
• Dowdeswell, Julian; Elverhøi, Anders; Andrews, J.Y. & Hebbeln, D. (1999). Asynchronous deposition of ice-rafted layers in the Nordic seas and North Atlantic Ocean. Nature.  ISSN 0028-0836.  400, s 348- 351
• Forsberg, C.F.; Solheim, Anders; Elverhøi, Anders; Jansen, E.; Channell, J.E.T. & Andersen, E.S. (1999). The Depositional Environment of the Western Svalbard Margin during the Late Pliocene and the Pleistocene: Sedimentary Facies Changes at Site 986. Proceedings of the Ocean Drilling Program.  162, s 233- 246
• Mohrig, B.D.; Elverhøi, Anders & Parker, Gary (1999). Experiments on the relative mobility of muddy subaqueous and subaerial debris flows, and their capacity to remobilize antecedent deposits. Marine Geology.  ISSN 0025-3227.  154, s 117- 129
• Dowdeswell, Julian A.; Kenyon, Neil H.; Elverhøi, Anders; Laberg, Jan Sverre; Hollender, F.-J.; Mienert, Jurgen & Siegert, M.J. (1996). Large-scale sedimentation on the glacier-influenced Polar North Atlantic margins: long-range side-scan sonar evidence. Geophysical Research Letters.  ISSN 0094-8276.  (23), s 3535- 3538 . doi: 10.1029/96GL03484

View all works in Cristin

• Stenseth, Nils Christian & Elverhøi, Anders (2014). VISTA Strategy 2014 - 2019.
• Kristoffersen, Yngve; Elverhøi, Anders & Eldholm, Olav (2013). Nansens arv. Dagsavisen.  ISSN 1503-2892.  s 4
• Wilhite, Harold Langford; Elverhøi, Anders; Bakken, Vebjørn; Winther, Tanja; Braa, Kristin & Geirbo, Hanne Cecilie (2012). Social impacts of electricity in rural areas.
• Breien, Hedda; De Blasio, Fabio V; Elverhøi, Anders; Nystuen, Johan Petter & Harbitz, Carl Bonnevie (2011). Transport mechanisms of sand in deep-marine environments-insights based on laboratory experiments - reply. Journal of Sedimentary Research.  ISSN 1527-1404.  81(11-12), s 842- 843 . doi: 10.2110/jsr.2011.68
• Wilhite, Harold Langford; Lien, Marianne Elisabeth & Elverhøi, Anders (2009). Klimasatsning på tvers. Aftenposten (morgenutg. : trykt utg.).  ISSN 0804-3116.
• Gauer, Peter; De Blasio, Fabio V & Elverhøi, Anders (2007). An international perspective I or II: dynamic modeling of submarine slide runout/submarine mass movements; where do we stand and what are the main challenges.
• De Blasio, Fabio Vittorio; Elverhøi, Anders; Engvik, Lars; Issler, Dieter; Gauer, Peter & Harbitz, Carl Bonnevie (2005). Understanding the high mobility of subaqueous debris flows. Show summary

  Submarine mass wasting shows a variety of forms like glacial mudflows, river-laden sedimentary failures, rock avalanches, sandy debris flows, outrunner blocks, or turbidity currents. In most cases, submarine mass flows reveal an extraordinary mobility, demonstrated by the very long runout distance between the source area and the final deposit, even on very gentle gradients. As an example, the front of the giant Storegga landslide in the Norwegian Sea covered a maximum distance of more than four hundred kilometres, running on an average slope angle of about one degree. This high mobility seems to affect all kinds of gravity mass flows, irrespective of the composition and grain size. Laboratory experiments, however, reveal that the dynamical behaviour of artificial debris flows depends dramatically on the clay-sand ratio in the experimental slurry. Artificial debris flows with high clay content, which are possibly a good replica of mudflows in glacially-influenced areas, tend to form a thin water layer at the front which acts as a natural lubricant. In contrast, lubrication cannot be easily invoked for sand-rich gravity flows. Indeed, the experiments show that sandy debris flows lack cohesion, and that sand settles quickly during the rapid disaggregating phase. In the present work, after briefly reviewing the field data, we present the experimental results gained with debris flows of various compositions, and finally examine the status of theoretical studies and numerical simulations of submarine debris flows. When dealing with debris flows which stay compact, such as clay-rich debris flows and outrunner blocks, the simulations reproduce well the lubrication effect seen in the experiments. On the other hand, sandy debris flows are far more complicated owing to the increased importance of water penetration, disintegration, and turbulence, and these difficulties will be reflected in greater intricacy with computer simulations. Thus, the problem of whether sandy debris flows may be highly mobile in the natural setting still remains elusive. We suggest some experiments and numerical models that might shed some light on this problem.

• de, Blasio Fabio V; Gauer, Peter; Issler, Dieter; Ilstad, Trygve; Elverhøi, Anders & Harbitz B, Carl (2005). Laboratory and field investigations on the long runout of submarine debris flows.
• Elverhøi, Anders; de, Blasio Fabio V; Engvik, Lars; Issler, Dieter; Nystuen, Johan Petter; Harbitz B, Carl; Ilstad, Trygve & Gauer, Peter (2005). Understanding the high mobility of subaqueous debris flows.
• Engvik, Lars; de, Blasio Fabio V & Elverhøi, Anders (2005). Snall scale simulations of outrunner blocks.
• Gauer, Peter; Elverhøi, Anders & de, Blasio Fabio V (2005). On numerical simulations of subaqueous slides: Back-calculations of laboratory experiments.
• Issler, Dieter; de, Blasio Fabio V; Gauer, Peter; Elverhøi, Anders & Harbitz B, Carl (2005). Emerging insights on the dynamics of submarine debris flows.
• Lastras, Galderic; de, Blasio Fabio V; Canals, Miquel; Elverhøi, Anders & Urgels, R (2005). Conceptual and numerical modeling of the BIG'95 debris flow, Western Mediterranean Sea -review.
• Engvik, Lars; De Blasio, Fabio Vittorio & Elverhøi, Anders (2005). Small scale simulations of outrunner blocks. Show summary

  Nedenfor undersjøiske skredavsetninger kan en ofte nedenfor finne løsrevne blokker som har beveget seg en betydelig avstand uten å brekke opp. Disse skredblokkene har vist seg å kunne bevege seg over store avstander med meget liten helning. De opptrer både i forbindelse med undersjøiske skred i eksperimentelle småskalaeksperimenter, så vel som i stor skala på havbunnen. En numerisk modell er utviklet som beskriver de viktigste delene av dynamikken til skredblokk. Beregninger er utført for ulike helningsvinkler og skredblokker med ulik geometrisk form ved små og moderate Reynolds tall. Resultatene er konsistente med observasjoner i eksperimenter. En kritisk hastighet blir påvist der blokkens front løfter seg og den videre bevegelsen blir ustabil. Den kritiske hastigheten avhenger hovedsakelig av tykkelsen til blokken. Submarine debris flows deposits are often accompanied by isolated blocks located some distance beyond the rest of the failed mass. These so-called outrunner blocks have proven the ability to travel over long distances on very gentle slopes. This phenomenon is observed at small scale experimental slides as well as in field scale. The aim of this work is to separate some of the most important features of the dynamics of outrunner blocks and study them in more detail in a manageable model. Simulations have been performed for several slope angles, shapes of the block at low and moderate Reynolds numbers. The results are consistent with experiments. A critical velocity is found, which is mainly related to the thickness of the block, where the front of the block lifts up and the motion become unstable.

• de, Blasio Fabio V; Ilstad, Trygve; Elverhøi, Anders; Harbitz, Carl Bonnevie & Issler, Dieter (2004). Flow, disintegration and lubrication of clayey-sandy debris flows: from laboratory to the field.
• de, Blasio Fabio V; Ilstad, Trygve; Elverhøi, Anders; Issler, Dieter & Harbitz, Carl Bonnevie (2004). Experiments on subaqueous mass transport with variable sand-clay ratio.
• de, Blasio Fabio V; Ilstad, Trygve; Elverhøi, Anders; Issler, Dieter & Harbitz, Carl Bonnevie (2004). High mobility of subaqueous debris flows and the lubricating-layer model.
• Elverhøi, Anders; de, Blasio Fabio V; Ilstad, Trygve; Harbitz, Carl Bonnevie & Issler, Dieter (2004). High mobility of sub aqueous debris flows and the lubricating layer model (1).
• Ilstad, Trygve; Longva, Oddvar; Elverhøi, Anders; Marr, Jeffrey G & Parker, Gary (2003). Outrunner blocks: Summary of observed behaviour in laboratory, and comparison to field deposits. Show summary

  This paper will focus on the development and flow of hydroplaning blocks in laboratory experiments, and depositional features will be compared to documented observation of field deposits of outrunner blocks. The debris flow experiments were performed in a 2.25 m wide and 9.0 m long slope inside a long channel. Subaqueous flows are run down the slope over a hard granular coated bed. The head tank was loaded with 680 kg of sediments which was released through a head gate. Experiments were filmed during the flow event and depositional features were documented with pictures. Outrunner blocks are documented in front of submarine slides in both fjords and on the continental slope (Johns et al., Kuijpers et al., Nissen et al.). These blocks run in front of the slide and maintains a higher speed than the main body of the slide, and may have a much longer runout than the main slide. Survey and core sampling from the Finneidfjord slide in Norway gives new data for in-depth analysis of outrunner blocks. In the process of risk analysis of on-bottom offshore and nearshore installations it is very important to understand how these blocks are developed and how far they will be transported. Experiments combined with depositional features in field gives new insight into development and flow mechanisms for glide block

• Elverhøi, Anders; Blasio, Fabio V. de; Butt, Faisal Ahmed; Issler, Dieter; Harbitz, Carl Bonnevie; Engvik, Lars; Solheim, Anders & Marr, Jeffrey G (2002). Submarine mass-wasting on glacially-influenced continental slopes: processes and dynamics.
• Ilstad, Trygve; Elverhøi, Anders; Issler, Dieter & Blasio, Fabio V. de (2001). Submarine mass flow, the transition from viscoplastic to granular flow.
• Elverhøi, Anders (2000). Når kommer neste istid.
• Norum, Kaare Reidar; Christophersen, Nils Damm; Elverhøi, Anders; Grue, John & Uggerud, Einar (2000). Hånd i hånd med næringslivet. Dagens næringsliv.  ISSN 0803-9372.
• Butt, Faisal Ahmed; Elverhøi, Anders; Solheim, Anders; Dimakis, P. & Hjelstuen, B.O. (1999). Relieff of the Barents Sea during Plio-Pleistocene and its implication for northern hemisphere glaciations.
• Elverhøi, Anders (1999). Fagutvalget for geo-fag.
• Elverhøi, Anders (1999). Hvorfor går skred på havbunnen mye lengre enn skred på landjorda.
• Elverhøi, Anders (1999). "Internasjonal evaluering av norsk geoforskning - en orientering.".
• Elverhøi, Anders (1999). "The Role of Hydroplaning in Subaqueous Mass Transport as Ascertained by Integrating Field Data with Experiment and Theoretical Studies.".
• Elverhøi, Anders; Dimakis, P.; Harbitz, Carl Bonnevie; Høeg, Kaare; Solheim, Anders; Laberg, J.S. & Vorren, T. (1999). "Submarine slope stability and generation of debris flows on high latitude glaciated margins".
• Elverhøi, Anders & Harbitz, Carl Bonnevie (1999). "The dynamics of subaqueous muddy debris flows - the importence of hydroplaning.".
• Harbitz, Carl Bonnevie & Elverhøi, Anders (1999). "Hydroplaning of subaqueous muddy debris flows-critical conditions and applications".
• Harbitz, Carl Bonnevie & Elverhøi, Anders (1999). On tsunami characteristics and submarine slide dynamics.
• Kenyon, Neil H.; Clark, J.D.; Dowdeswell, Julian A.; Elverhøi, Anders; Ivanov, M.; Laberg, Jan Sverre; Mienert, Jurgen & Millington, J. (1996). Comparison of major downslope mass transport systems on low and high latitude continental slopes.

View all works in Cristin