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13. Conceptual diagram showing stages in the evolution of the Mount Meager debris avalanche. (1) The south flank of Mount Meager fails. (2) The rock mass breaks up, spreads, and liquefies as it begins to accelerate down Capricorn Creek valley. Water escapes from beneath the debris avalanche, forming the advance water-rich phase (blue line); the bulk of the mass, in comparison, is relatively dry (red line). Although the two phases interact, they follow different paths and leave separate deposits. (3) Both phases achieve very high velocities before impacting the south valley wall of Meager Creek. They decelerate as they spread up and down Meager Creek and into Lillooet River valley. (4) Final deceleration and cessation of flow.
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Mount Meager is a glacier-clad volcanic complex in British Columbia, Canada. It is known for its landslides, of which the 2010 is the largest Canadian historical landslide. In this thesis we investigated slope instability processes at Mount Meager volcano and the effects of ongoing deglaciation. We used a variety of methods including field and remo...
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![Figure 1. Centred on [37.8935,-119.2021] showing remnant glacier ice...](profile/Brian-Whalley/publication/363214658/figure/fig1/AS:11431281082686171@1662114013116/Centred-on-378935-1192021-showing-remnant-glacier-ice-patches-1-5-Randolph_Q320.jpg)
The Posteroutlines the use of downslope transects that map landform elements (such as Rock free face, Scree slopes) that supply debris to small glacier systems, thus becoming, in their lower reaches, rock glaciers. Examples are given from the Bashgal Valley, Eastern Hindu Kush in 1976 and from 2019 Google earth Images
The poster also contains a se...
Citations
... Rather, Curtis (2016) suggested that new glaciovolcanic cave development may indicate subnivean volcanic unrest. A recent example of glaciovolcanic cave genesis in the glacier at Mount Meager, Canada have raised concerns about renewed volcanic hazards (Roberti, 2018;Unnsteinsson, 2022). ...
The twin summit craters of Mount Rainier, Washington, USA host the largest known glaciovolcanic caves in the world and at 4382 m, the highest elevation caves in the USA. The caves are formed in ice at the glacier-rock interface by volcanogenic gases and atmospheric advection. However, the way in which discrete caves are formed and evolve remains poorly understood. Surveys of the cave systems in 1970−1973 and 1997−1998 in both the West and East Craters documented cave passage morphology. Field expeditions from 2014−2017 comprehensively surveyed the Rainier summit caves and undertook thermal imaging and temperature monitoring. Significant changes had occurred. In the East Crater, documented cave length has nearly doubled since 1973 to 3593 m of passage spanning 144 m of depth, revealing a new subglacial lake, and now nearly circumnavigating the East Crater. Of the reported increase in length, some 600 m of the mapped passage is possibly newly formed. Across 47 years of observation, certain sections of the cave appear to be preserved in form and position through time, while others are more actively being lost or forming. Conserved passages are generally sub-horizontal, passages following the curvilinear crater contours, show low temperature variability, and are dependent on perennial fumarolic activity or distributed heat flux emanating from warm bedrock and sediment floors. Transient passages are smaller diameter dendritic passages following the slope of the ice-rock interface towards entrance zones and normal to the circum-crater passage. They also show higher variability in temperature and airflow and are subject to seasonal weather and mechanical collapse, which may contribute to transience. Additional research is required to confirm the mechanisms maintaining conserved passages and formation of transient passages.
... Hetherington (2014 and references therein) identify unstable areas on the western side of Plinth Peak and note that the eastern flank appears to have a very low factor of safety that can be presumed to be at the point of failure. The failure surface is described as being deep (Hetherington, 2014;Roberti, 2018;Roberti et al., 2021) such that should a landslide occur in this location, a major bulk of Plinth Peak could fail. Consequently, as with the 2010 landslide, it could dam the Lillooet River and cause widespread flooding downstream. ...
Landslides and slope failures represent critical hazards for both the safety of local communities and the potential damage to economically relevant infrastructure such as roads, hydroelectric plants, pipelines, etc. Numerous surveillance methods, including ground-based radar, InSAR, Lidar, seismometers, and more recently computer vision, are available to monitor landslides and slope instability. However, the high cost, complexity, and intrinsic technical limitations of these methods frequently require the design of alternative and complementary techniques. Here, we provide an improved methodology for the application of image-based computer vision in landslide and rockfall monitoring. The newly developed open access Python-based software, Akh-Defo, uses optical flow velocity, image differencing and similarity index map techniques to calculate land deformation including landslides and rockfall. Akh-Defo is applied to two different datasets, notably ground- and satellite-based optical imagery for the Plinth Peak slope in British Columbia, Canada, and satellite optical imagery for the Mud Creek landslide in California, USA. Ground-based optical images were processed to evaluate the capability of Akh-Defo to identify rockfalls and measure land displacement in steep-slope terrains to complement LOS limitations of radar satellite images. Similarly, satellite optical images were processed to evaluate the capability of Akh-Defo to identify ground displacement in active landslide regions a few weeks to months prior to initiation of landslides. The Akh-Defo results were validated from two independent datasets including radar-imagery, processed using state of the art SqueeSAR algorithm for the Plinth Peak case study and very high-resolution temporal Lidar and photogrammetry digital surface elevation datasets for the Mud Creek case study. Our study shows that the Akh-Defo software complements InSAR by mitigating LOS limitations via processing ground-based optical imagery. Additionally, if applied to satellite optical imagery, it can be used as a first stage preliminary warning system (particularly when run on the cloud allowing near real-time processing) prior to processing more expensive but more accurate InSAR products such as SqueeSAR.
... New examples at Mount Meager, Canada, in the Garibaldi volcanic belt further reinforce the dynamic nature of glaciovolcanic caves and their impacts to volcanic hazard detection (Fig. 3). Two new glaciovolcanic cave entrances were detected in the Job Glacier of the Mount Meager Volcanic Complex, signalling potential changes in the edifice of Canada's only active volcano (Roberti et al. 2018). Continued study of this example includes models of the cave/chimney formation (Unnsteinsson et al. 2020) alongside volcanic hazard and landslide monitoring. ...
Enhanced thermal flux from volcanic emissions can melt ice and enlarge voids at the interface between the lithosphere and cryosphere. On volcanic edifices mantled with glaciers, glaciovolcanic caves develop in association with this melt and advection of volcanic outputs. This short paper discusses the genesis and morphologies of these phenomena from a pseudokarst perspective and highlights examples around the world, with a focus on current research in the Cascade volcanoes of the Pacific Northwest, USA.
... Rapid retreat of Capricorn Glacier from the 1980s until 2010 probably provided a long-term water input to the colluvium and fractured rock involved in the 6 August 2010 failure area. Advanced InSAR analysis of archival ERS scenes (1992e2000) indicates radar line-of-sight displacements on the order of 7e17 mm/a for similar slopes along the northern part of the massif (Roberti, 2018); the true motion vectors are likely slightly greater. p0220 ...
Landslides in bedrock are an integral component of the landscape’s erosional
response to tectonic uplift (Densmore et al., 1997; Montgomery and Brandon,
2002; Korup et al., 2007). They involve volumes, velocities and frequencies
that vary over many orders of magnitude (Guzzetti et al., 2012). Bedrock
landslides can be very rapid ranging from small frequent rockfalls to large
infrequent rockslides and rock avalanches, but can also occur as slower,
continuous or episodic, deep-seated deformation of extensive slopes. Characterising
the hazard associated with bedrock landslides requires an understanding
of multiple attributes, contributing factors, and processes. These
include mechanical properties of intact rock, orientation and surface characteristics
of discontinuities, geologic history of the rock mass and topography of
the slope including past and currently active tectonic, and geomorphic processes
(Griffiths et al., 2012; Frattini and Crosta, 2013). The spatial distribution
of bedrock landslides is strongly influenced by tectonic structures
(Agliardi et al., 2001; Jaboyedoff et al., 2013; Stead and Wolter, 2015). Their
spatiotemporal distribution can also be influenced by external factors such as
weather (Macciotta et al., 2015), climate (Gariano and Guzzetti, 2021),
earthquakes (Keefer, 1984; Fan et al., 2019; Murphy, 2021), and anthropogenic
activities (Heim, 1932; Mueller, 1964). Differing spatial distributions for
earthquake-triggered and rainfall-triggered landslides have been documented
by Huang and Montgomery (2014) for discrete events and Wang et al. (2020)
over millennial time scale. These findings confirm Densmore and Hovius’
(2000) hypothesis that earthquake-triggered landslides tend to occur along
ridges, where ground acceleration is amplified by topography, whereas
rainfall-triggered landslides occur lower on slopes, corresponding to zones of
groundwater discharge. Contributing factors and triggers of mass movements
are discussed in more details in McColl (2021).
... We used pre-existing large-scale maps of Read (1979) and Woodsworth (1977) as well as our field mapping to accurately depict unit locations and contacts. The youngest MMVC eruption, 2350 B.P Pebble Creek Formation (PcF) (Hickson et al., 1999;Stewart et al., 2008) and youngest landslide (2010) (Roberti et al., 2018) ...
... We used the pre-existing maps of Read (1979) and Woodsworth (1977) in conjunction with our results from the 2019 and 2020 field seasons to create the bedrock interface map (Fig. 2). The youngest MMVC eruption, 2350 B.P Pebble Creek Formation (Hickson et al., 1999;Stewart et al., 2008) and youngest landslide (2010) (Roberti et al., 2018) are also distinguished (Fig. 2). ...
... This inconsistency may be due to the rate of uplift, direction of modern plate movement within SW BC, and most importantly, movement of individual basement blocks in the region. The Garibaldi Volcanic Belt is tectonically active with very high rates of uplift (Parrish, 1982;Ryder et al., 1991;Roberti, 2018). ...
... We used pre-existing large-scale maps of Read (1979) and Woodsworth (1977) as well as our field mapping to accurately depict unit locations and contacts. The youngest MMVC eruption, 2350 B.P Pebble Creek Formation (PcF) (Hickson et al., 1999;Stewart et al., 2008) and youngest landslide (2010) (Roberti et al., 2018) ...
... We used the pre-existing maps of Read (1979) and Woodsworth (1977) in conjunction with our results from the 2019 and 2020 field seasons to create the bedrock interface map (Fig. 2). The youngest MMVC eruption, 2350 B.P Pebble Creek Formation (Hickson et al., 1999;Stewart et al., 2008) and youngest landslide (2010) (Roberti et al., 2018) are also distinguished (Fig. 2). ...
... This inconsistency may be due to the rate of uplift, direction of modern plate movement within SW BC, and most importantly, movement of individual basement blocks in the region. The Garibaldi Volcanic Belt is tectonically active with very high rates of uplift (Parrish, 1982;Ryder et al., 1991;Roberti, 2018). ...
In summer 2019, we carried out an intense two weeks of field geology mapping, north of Mt. Meager, at the northern Lillooet ridge. We also mapped a small part of southwestern contact of Mt. Meager, adjacent to Peter Reads (1990) geology map. We mapped both young volcanic rocks and basement rocks and collected structural data such as faults, folds, fractures and attitude of beddings and planar features. Interpretation of our data on the North Lillooet ridge indicates the presence of major strike-slip movement, at least two stages of deformation, and basement block tilting or potential basement block rotation. Strike-slip and normal faults of southwestern Meager has similar structural trends with strike-slip and normal faults on the North Lillooet ridge.
In summer 2020, paleomagnetic samples were drilled at the following five sites (Fig. 10): On the eastern ridge, site 1 and site 2 were drilled on the undated andesitic lava, with site 1 stratigraphically located above site 2; site 3 was drilled on pink granite basement rock which was in sharp contact with the andesitic lava. On the western ridge, site 4 was drilled on the large vertically jointed dacite lava flow; site 5 was drilled on older basement granodiorite rocks.
To summarize, we can list results of this work in the following points:
1. This field geology data, including outcrop scale, structural geology (faults, folds, joints, and attitude of basement units) mapped on the north Lillooet Ridge, north of the Mt. Meager massif indicate the presence of an E-W striking left-lateral strike-slip fault between east and west ridges at North Lillooet Ridges. Although, the two minor folds on the western ridge (see figure 5B show more northerly trend of NNE-SSW direction)) should have a fold axis orientation (trend) NW-SE. But as it explained could have been affected by the possible rotation of the fault blocks and possible subsequent deformation stages
2. Our preliminary paleomagnetic directional study for the young volcanic rocks (between 2 Ma to 0 Ma) agrees with the presence of a left-lateral strike slip fault and suggests an anticlockwise rotation of approximately 10 to 20 degrees on the eastern ridge and more than 40 degree tilting on the western ridge (Table 1 and Fig. 11).
3. The current paleomagnetic data, along with the structural geologic fieldwork including cross-cutting relationships of faults within the basement and younger lavas, indicates that both dacitic and andesitic lava flows on the North Lillooet ridge either predate faulting or were deposited during faulting.
4. If our preliminary pilot paleomagnetic results are accurate, Mt. Meager, and more specifically, North Lillooet ridge, was tectonically active at least between 300-700 ka or between 2-1.2 Ma.
... A narrow outcropping of monolithic stacked breccia (NLmcB) (Fig. 4) is exposed within a N-S valley roughly 50 m SE of the NLvjL, and is exposed directly Our 2019 mapping campaign included new mapping of a lava (PPbjL) (Fig. 2a) situated ~1 km west of the Mount Meager summit. The lava is visible at an elevation of 2,360 m on the west side of the glacial valley beneath Perkins Pillar, and was first described by Roberti (2019) during fieldwork. The lava is dark grey, plagioclase, biotite, and hornblende porphyritic, and is exposed by recent glacial retreat near the Mount Meager summit. ...
Exploring geothermal energy as a source of renewable energy is appealing due to its limited environmental impact; however, there is substantial economic risk due to development costs and large uncertainties in the properties of the subsurface reservoir rocks. Subsurface models of geology are paramount for evaluating reservoir capacity, zones of permeability, fracture or fault patterns, and ultimately reducing the exploration risk. The overarching goal for this work is to contribute information that can be used to assess the geothermal potential underlying Mount Meager of Southwest British
Columbia (BC) (Fig. 1). Mount Meager (Fig. 1) is a volcanic complex situated 160 km N of Vancouver and is part of the Garibaldi Volcanic belt (GVB) which, itself, represents a northern segment of the Cascade
Volcanic Arc into Canada.
This specific contribution comprises a large-scale field mapping campaign focussed on bedrock structural analysis and expansion of the regional mapping to include unmapped young volcanic centres on the peripheral margins of Mount Meager. Our work expands on two previous major mapping campaigns conducted by Woodsworth (1977) and Read (1977). Woodsworth mapped the entire Pemberton region including the coastal plutonic and metasedimentary uplifted basement rocks and episodic volcanic deposits. The scale of Woodsworth’s map was large and, thus, volcanic units around Mount Meager were only distinguished by age between Miocene to Pleistocene. In contrast, Read’s map was finer scale and focused exclusively on the geology of the Mount Meager massif; he identified more than thirty map units comprising intrusive or extrusive igneous deposits, which were assigned to “assemblages” based on relative and absolute age relationships. Subsequent work by Green et al. (1988), and Stasiuk and Russell (1989, 1990) built upon the mapping by Woodsworth and Read and produced petrologic and geochemical classifications for the eruptive rocks of Mt Meager, with correlating age constraints ranging from 2.2 to less than 0.1 Ma (Green et al., 1988). Our work here builds upon these
previous studies.
... The eruptive suite includes pyroclastic deposits, overlapping andesite and rhyodacite flows, and dacite domes, as well as peripheral basaltic flows (Read, 1990;Hickson et al., 1999). The volcanic deposits, which, on average, form the upper 600 m (topographic) of the complex, overlie Mesozoic plutonic and metamorphic basement rocks (Read, 1990;Roberti, 2018). ...
Warwick, R.K., Williams-Jones, G., Witter, J., & Kelman, M.C. (2019) Comprehensive Volcanic-Hazard Map for Mount Meager Volcano, Southwestern British Columbia (Part of NTS 092J). in Geoscience BC Summary of Activities 2018 - Energy and Water, Geoscience BC, Report 2019-2, 85-94.
... Observed ground deformation is scored 0 or 1. Canada does not routinely monitor volcano deformation with groundbased global positioning systems (GPS), tiltmeters, or remote sensing, although an Interferometric Synthetic Aperture Radar (InSAR) monitoring system is under development as part of Natural Resources Canada's Volcano Risk Reduction in Canada project Rotheram-Clarke et al. 2023). Previous InSAR, light detection and ranging (LI-DAR), Structure from Motion photogrammetry, analysis of glacier loss, and field mapping at Mt. Meager showed 27 large (>500 000 m 2 ) unstable slopes Roberti 2018). The movements detected included, during a 24-day period in the summer of 2016, displacements of up to 34 mm on the east flank of Job Creek and up to 36 mm on the east flank of Devastation Creek valley; a collapse of either of these two slopes could potentially produce a landslide of 100 million to 1 billion m 3 (Roberti 2018). ...
... Previous InSAR, light detection and ranging (LI-DAR), Structure from Motion photogrammetry, analysis of glacier loss, and field mapping at Mt. Meager showed 27 large (>500 000 m 2 ) unstable slopes Roberti 2018). The movements detected included, during a 24-day period in the summer of 2016, displacements of up to 34 mm on the east flank of Job Creek and up to 36 mm on the east flank of Devastation Creek valley; a collapse of either of these two slopes could potentially produce a landslide of 100 million to 1 billion m 3 (Roberti 2018). Current InSAR monitoring at Mt. Meager has detected other ongoing slope movements (e.g., at Mosaic Creek). ...
... Mt. Meager in particular has been the focus of a significant proportion of volcanological research in Canada, primarily due to its 2360 BP explosive eruption (Clague et al. 1995;Leonard 1995), geothermal potential (Grasby et al. 2012(Grasby et al. , 2020(Grasby et al. , 2021Witter 2019), and recent history of large debris flows (Simpson et al. 2006;Friele et al. 2008;Guthrie et al. 2012;Roberti et al. 2017Roberti et al. , 2018Roberti et al. , 2021. The work includes a regional geological map (Read 1977), several higher resolution lithofacies studies targeting the 2360 BP VEI 4 event (Hickson et al. 1999;Stewart et al. 2002;Campbell et al. 2013;Andrews et al. 2014), a study of a pre-2360 BP eruption (Russell et al. 2021), intermittent remote sensing ground deformation studies (Roberti et al. 2017, a retrospective earthquake study (Lu and Bostock 2022), magnetotelluric imaging (Hanneson and Unsworth 2023, This Volume), gravity surveys (Calahorrano-Di Patre and Williams-Jones 2021), and infrequent hot spring water and fumarole gas chemistry sampling (Ghomshei et al. 1986;Venugopal et al. 2017). ...
We assessed 28 Canadian volcanoes in terms of their relative threats to people, aviation, and infrastructure. The methodology we used was developed by the United States Geological Survey for the 2005 National Volcano Early Warning System. Each volcano is scored on multiple hazard and exposure factors, producing an overall threat score. The scored volcanoes are assigned to five threat categories, ranging from Very Low to Very High. We developed a knowledge uncertainty score to provide additional information about assessed threat levels; this does not affect the threat scoring. Two Canadian volcanoes are in the Very High threat category (Mt. Garibaldi and Mt. Meager). Three Canadian volcanoes are in the High threat category (Mt. Cayley, Mt. Price, and Mt. Edziza) and one volcano is in the Moderate threat category (Mt. Silverthrone). We compare the ranked Canadian volcanoes to volcanoes in the USA and assess current levels of monitoring against internationally recognized monitoring strategies. We find that even one of the best-studied volcanoes in Canada (Mt. Meager) falls significantly short of the recommended monitoring level and is currently monitored at a level commensurate with a Very Low threat edifice. All other Canadian volcanoes are unmonitored (apart from falling within a regional seismic network). This threat ranking has been used to prioritize hazard and risk assessment targets and to help select monitoring activities that will most effectively address the undermonitoring of Canadian volcanoes.
The Mount Meager Volcanic Complex (Qwe̓ lqwe̓ lústen or Mt. Meager) coincides tectonically with the intra-arc to back-arc transition zone and exhibits the loci of strain partitioning in response to a rapid change in orientation of the Pemberton and Garibaldi Arc segments that are coeval with a shift in Pacific plate motion after 5 Ma. This strain partition is manifested through development of a transpressional deformation from 5 to 1.9 Ma at the latitude of Mt. Meager. Mt. Meager is an active volcanic system with at least two explosive eruptions in the last 25 000 years, the most recent occurring around 2360 BP. Additionally, it is the site of the largest landslide in Canadian history, which occurred during the summer of 2010, originating from the southeastern side the massif. During early exploration at Mt. Meager, geothermal boreholes drilled to 3 km reached 270 °C but did not find sufficient permeability to sustain self-flowing conditions. To understand the geological challenges in Mt. Meager’s geothermal exploration, we analyzed outcrop-scale faults and folds, incorporating structural mapping, volcanic rock paleomagnetism, and radiometric dating to establish kinematic history and kinematic compatibility of structural geology features, including faults and folds. Our findings suggest that stress partitioning during the last 5 Ma resulted in the formation of a transpressional structure exhibited as an elongate and rhomboidal structure at Mt. Meager with anomalously high topographic elevations which led to east northeast–west southwest crustal shortening and exhumation of crystalline basement. This new structural geology model improves our understanding of the geothermal reservoir and potentially significant geohazards.
