Debris flows, avalanches and other geophysical mass flows pose a significant hazard to settlements in or near mountainous regions. Understanding the physical processes that govern these flows is an essential part of hazard assessment and mitigation strategies. This thesis addresses two aspects of geophysical mass flows: flow self-channelisation due to the formation of lateral levees, and granular shocks, which occur when a rapidly-moving debris flow or avalanche collides with an obstacle. We present the results of large-scale debris flow experiments in which the flow is channelised by coarse-particle levees that form at the flow margins. The flow surface velocities are measured with high speed overhead photography, and the deposits both sampled to obtain the grain size distribution and excavated to recover the deposited locations of tracer pebbles that were introduced in to the flow. We propose a model, supported by evidence from the large-scale experiments, that describes in detail the size segregation and kinematic transport processes responsible for the deposition of lateral levees. The second problem addressed in the thesis concerns granular shocks, or jumps, which are rapid changes in the depth and velocity of granular avalanches. We investigate these through experiments in which a falling jet of granular material impacts on an inclined plane, generating a steady granular jump, which is either teardrop-shaped or 'blunted'. Numerical solutions of a depth-averaged flow model agree quantitatively with many of the observed flow features. We use this model show that the transition between the teardrop-shaped and blunted jump regimes corresponds to a transition between two shock reflection structures, known as a regular and a Mach shock reflection. On planes inclined at a shallow angle, we demonstrate a wide variety of unsteady and channelised flows, which occur due to the complex interaction between flowing and stationary regions of granular material.

Mt. Ruapehu is one of the most lahar prone volcanoes in the world, having both a crater lake and six small glaciers upon its 2797 m summit. The major outlet for the crater lake, the Whangaehu Gorge, has hosted over 46 historic lahars. However, the low preservation of debris flow deposits, as a result of frequent remobilisation on steep slopes, allows for the detailed description of only 9 lahar events over the last 150 years. Field investigation, historic aerial photos, two airborne LiDAR surveys and direct measurements have been utilised to describe the sedimentology, geomorphology and distribution of historic lahar deposits in the first 11 km of the Whangaehu Gorge. Inundation maps have been created for 1945, 1953, 1975, September 1995, October 1995, March 2007 and September 2007. Grain size distribution, componentry and geomorphology of the 1861, 1975, September 1995, October 1995, 1999 and 2007 lahar deposits have been compared. The lahar deposits are massive, very poorly sorted, silty gravels that form a series of unconsolidated terraces. The limited sediment sources in the steep sided Whangaehu Gorge, including minor historic eruption products, results in significant recycling of lahar deposits. However, the deposits can be differentiated by proportions of lithological components and in some cases anthropogenic debris. The abundance of hydrothermally altered material reflects the role of Crater Lake in lahar formation, although, some of these materials (gypsum, sulphur and snow) are only temporary. Non-cohesive debris flows and occasional snow slurry lahars have been formed by a range of triggering mechanisms associated with and independent of eruptions. Lahars have been formed in the Whangaehu Valley as the result of ejected crater lake water and associated snow melt (1975, September 1995 and September 2007), as well as the progressive displacement of lake water as a result of lava dome growth (1945) and uplift of the lake floor (1968). Inter-eruption lahars occur as a result of Crater Lake outburst floods (1861, 1953 and March 2007) and remobilisation by precipitation and the collapse of tephra laden snow (October 1995 and 1999). The comparison of historic lahars also reflects the range of lahar magnitudes experienced historically on Ruapehu. The most recent Crater Lake outburst of March 2007, with a peak discharge of 1700-2500 m3/s is the second largest recorded lahar, behind only the eruption-generated lahar of April 1975 with a peak discharge of 5000-7500 m3/s. Lahar mitigation can subsequently be based on lahar generation and incorporation of the vast amounts of data collected before and after the 2007 outburst flood. Recent remobilisation and phreatic activity suggest the significant under-representation of small volume events like rain-generated and snow slurry lahars in the geologic record.

The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km² (411-mi²) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration. / text

This study aims at uncovering the formation mechanism of the recent bright gully deposits observed on Mars in order to assess the viability of liquid water involvement. I use a high resolution topography model as input into a kinematic model to assess whether or not a dry granular flow could form the bright gully deposits seen in Hale Crater. I investigate a dry mechanism due to the difficulty of producing water on the martian surface under present-day pressure and temperature conditions. I examine a range of particle sizes, flow thicknesses, and upslope initiation points to examine how these parameters affect the run-out distances of flows. The results show that multiple combinations of parameters could produce flows that travel to within the observed deposits' boundaries. The results suggest that the recent bright gully deposits are not evidence of recent liquid water on the surface of Mars.

The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration.

The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration.

The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration.

The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration.

The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration.

The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration.