Earth Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

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The role of englacial hydrology in the filling and drainage of an ice-dammed lake, Kaskawulsh Glacier, Yukon, Canada

Author: 
Date created: 
2019-03-06
Abstract: 

Catastrophic drainage of glacier-dammed lakes can have significant downstream impacts. The role of the little-studied englacial hydrological system is investigated during the filling and drainage of an ice-marginal lake dammed by the Kaskawulsh Glacier in Yukon, Canada. Geophysical and hydrometeorological instruments were deployed to monitor the hydrology and dynamics of the lake--glacier system. Water-balance calculations reveal that of the ~44.1 million cubic metres of water in the catchment at peak lake level, the subglacial and englacial reservoirs store approximately 55% and 22%, respectively, compared to 23% in the subaerial lake. Abrupt changes in ice-shelf uplift rates, associated with fracturing and faulting, are linked to the redistribution of englacial water (1.6--6.6% estimated water content) based on borehole water-pressure and radar reflection-power data. Characterizing the dynamic coupling of the reservoirs, and the abrupt nature of connections between them, represents an advance in our conceptual understanding of glacier lake outburst floods.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Gwenn Flowers
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Time-lapse gravity monitoring at Cotopaxi volcano, Ecuador: A glimpse inside a restless colossus

Date created: 
2019-02-26
Abstract: 

Cotopaxi, a glacier-clad stratovolcano located in Ecuador, showed signs of unrest in April 2015, which ramped up until August 14, 2015, with the advent of phreatomagmatic explosions. Time-lapse gravity measurements started at Cotopaxi volcano in June 2015. Minor gravity changes were detected prior to eruptive activity, however, the largest gravity variations at Cotopaxi were measured between October 2015 and March 2016, as other geophysical parameters reached background levels. Inverse modelling using GPS data pointed towards a deep intrusion prior to eruptive activity, while inverse modelling of post-eruptive gravity data fit with changes in the hydrothermal system. A deep magmatic source intruded between April and August 2015, leading to measured deformation and seismicity, while an inferred shallow source rose from depth and interacted with the hydrothermal system, causing the phreatomagmatic activity. Hydrothermal fluids were pushed from a deep aquifer into a shallow perched aquifer, and caused time-lapse gravity variations.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Glyn Williams-Jones
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

The Eastern Flank: Predicting the Architecture of the McMurray Formation Beyond its Subcrop Edge

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2018-07
Abstract: 

Lower Cretaceous sediment was delivered to the McMurray Sub-Basin, probably via a continental-scale drainage system with headwaters in the Canadian Shield, Appalachians, and Cordillera of North America. Towards the mouth of the continental-scale drainage, a series of tributaries drained the Canadian Shield, although the number, scale, and position of tributaries is poorly constrained. Herein, the McMurray paleodrainage system is mapped from the main fairway east towards the sparsely drilled and erosionally truncated subcrop edge. Linear and exponential regression is then used to map the McMurray Fm to its theoretical eastern extent. Interpretations provided in this study indicates Assiniboia Valley, trunk valley of the McMurray Fm drainage, is not substantially wider than currently mapped, and the currently identified axis of Assiniboia Valley is accurate. However, the tributary network entering Assiniboia Valley from the Canadian Shield is complex with three main tributaries identified: Firebag, Buffalo River, and Choiceland tributaries.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Shahin Dashtgard
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Refining the chronostratigraphy of the Lower Nanaimo Group, Vancouver Island, Canada, using detrital zircon geochronology

Author: 
Date created: 
2018-12-17
Abstract: 

Convergent-margin basins (CMBs) are rich in broadly coeval detrital zircon (DZ) owing to the proximity of active magmatic belts. Consequently, DZ geochronology can be employed to assess the utility of stratigraphic frameworks developed for these basins. This study uses DZ data to assess the utility of lithostratigraphy developed for the Cretaceous-aged lower Nanaimo Group in the Georgia Basin, Canada. Results show that the basal lithostratigraphic unit of the Nanaimo Group, the Comox Formation, comprises strata that are neither time correlative nor genetically related. The three lithostratigraphic units directly overlying the Comox Formation (Haslam, Extension, and Protection formations) comprise strata with similar genetic affinities, indicating that deposition of these units was not entirely sequential, and contemporaneous in some locales. Further, sediment provenance evolved through time, which the existing lithostratigraphic framework does not reflect. This work demonstrates that DZ geochronology can effectively test the utility of stratigraphic frameworks in CMBs.

Document type: 
Thesis
Senior supervisor: 
Shahin E. Dashtgard
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Early evolution of a forearc basin: Georgia Basin, Vancouver Island, Canada

Author: 
Date created: 
2018-12-18
Abstract: 

The Late Cretaceous lower Nanaimo Group was deposited in the forearc Georgia Basin of BC, Canada along the western margin of the Canadian Cordillera, and records its initiation and early depositional evolution. Nanaimo Group strata are currently subdivided into 11 lithostratigraphic units, which are identified based on lithology, texture (i.e., dominantly coarse- or fine-grained), and position relative to the basal nonconformity and to one another. Paleotopography on the basal nonconformity, however, ensures that these lithostratigraphic units are not time correlative, and hence, cannot reliably be used to reconstruct basin evolution. Herein, transgressive-regressive sequence stratigraphy is employed to construct a stratigraphic framework for the lower Nanaimo Group. Eight depositional phases are identified in the lower Nanaimo Group. Depositional phases are separated by flooding surfaces, regressive surfaces, or unconformities. The stratigraphy of the lower Nanaimo Group reflects net transgression, manifested as an upwards transition from braided fluvial conglomerates through to marine mudstones.

Document type: 
Thesis
Senior supervisor: 
Shahin Dashtgard
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

An investigation into the time dependent deformation behaviour of open pit slopes at Gibraltar Mine, BC, Canada

Author: 
Date created: 
2018-12-18
Abstract: 

Open pit slope instabilities experience a sequence of decelerating deformation events following changes in stress state due to blasts or mining. These deformation events are poorly understood. This thesis uses large databases of specific energy and slope radar monitoring data to characterise five slope instabilities. Eight different rheological and empirical curve-fitting models are applied to 24 deformation events to identify which model best approximates observed deformation. The best-performing model, the Fractional Maxwell model, is then applied to nearly 200 deformation events identified from the five slope instabilities. The resulting model parameters α, fractional viscosity, and A, magnitude of the response, are tracked and compared with deformation history, instability size and geometry, and blast size and location. Slope instabilities exhibit increasingly viscous behaviour with deformation as damage accumulates within the rock mass. The magnitude and likelihood of deformation events correlate with the proximity of the stress change to critical geological structures.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Doug Stead
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Sedimentological and ichnological characterization of small- and large-scale channel IHS in the Middle McMurray Formation of the Central-C area, McMurray Sub-Basin, Alberta

Author: 
Date created: 
2018-12-11
Abstract: 

The Lower Cretaceous McMurray Formation is interpreted as a brackish-water, tidally influenced estuarine complex. The study area encompasses Townships 90-95, Ranges 10-14W4 in northeast Alberta. Facies analysis of 41 cored wells led to the identification and differentiation of large- and small-scale lateral accretion IHS associated with tidal-fluvial channels. Five sedimentary facies are assembled into four recurring facies associations to characterize these channel systems. Sedimentological and ichnological characteristics point to elevated physico-chemical stress in most large-scale channel successions, interpreted to be the consequence of carrying the bulk of the fluvial discharge through these trunk channel systems. By contrast, small-scale channels display less evidence of physico-chemical stress indicating they carried little fluvial flow. Abandoned channel deposits likewise show reduced paleoenvironmental stress. This study suggests that the deposits of small-scale channels and abandoned channels are the most suitable for assessing the degree of marine influence in the study area.

Document type: 
Thesis
Senior supervisor: 
James MacEachern
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Mount Meager, a glaciated volcano in a changing cryosphere: hazard and risk challenges

Author: 
Date created: 
2018-10-24
Abstract: 

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 remote, geological, geomorphological and structural mapping to characterize glacial and landslide activity at Mount Meager. We used Structure from Motion photogrammetry (SfM) and Lidar to produce digital surface models and InSAR to monitor slope deformation. We applied SfM to historic photography to document glacier and landslide activity at Mount Meager. We discussed a model of growth and erosion of a volcano in glacial and interglacial periods, and the scientific and dissemination value of historic 3D topographic reconstruction. We described the 2010 Mount Meager landslide deposit to interpret emplacement dynamics and kinematics. The 2010 landslide separated in water-rich and water-poor phases that had different runout and distinct deposits. We analyzed historic airphotos to constrain the slope deformation prior to the 2010 collapse. The glacier near the toe of the slope retreated in the failure lead up, the collapse evolved in four subfailures involving the whole volcanic sequence and some basement rocks. We estimated 6 × 106 m3 of water in the slope, that allowed the separation of the frontal water-rich phase. The total failure volume was 53 ± 3.8 × 106 m3. We identified 27 large (>5×105 m2) unstable slopes at Mount Meager and calculated ~1.3 km3 of ice loss since 1987. The west flank of Plinth peak and Devastation Creek valley moved up to -34±10 mm and -36±10 mm, respectively, over a 24-day period during the summer of 2016. The failure of these slopes could impact infrastructures and communities downstream of the volcano. The resulting decompression on the volcanic edifice after the failure of Plinth peak would affect the stress field to a depth of 6 km and up to 4 MPa. This sudden decompression could lead to hydrothermal or magmatic eruptions

Document type: 
Thesis
File(s): 
Senior supervisor: 
Brent Ward
Benjamin van Wyk de Vries
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Characterization of landform evolution and slope response to the 2015 earthquake sequence and annual monsoon in Central Nepal

Author: 
Date created: 
2018-06-26
Abstract: 

The April 25th, 2015 Mw 7.8 Gorkha earthquake triggered thousands of co-seismic landslides across Central Nepal. This thesis investigates the evolution and controls on co- and post-seismic mass movements at two case study slopes, Tushare and The Last Resort using a range of remote sensing techniques collected prior to and following the 2015 earthquakes over the five-year period from 2012 to 2017. A range of remote sensing techniques including terrestrial laser scanning, digital photography, photogrammetry, and satellite imagery were used to characterize the landslides at these slopes. Engineering geological and geomorphological mapping and three-dimensional rockfall modelling were employed to analyze structural controls on mass movements. Analysis of surface change using change detection techniques was used to evaluate landform evolution at the slopes in response to the earthquakes and 2015 to 2017 annual monsoons. Observed post-seismic instability is dominated by reactivation of colluvium from the co-seismic failures as opposed to initiation of new failures. Elevated landslide hazard associated with loose debris on the slopes is anticipated to continue in future monsoons.

Document type: 
Thesis
Senior supervisor: 
Doug Stead
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Snow drought and streamflow drought in western North America in the context of a warming climate

Author: 
Date created: 
2018-08-17
Abstract: 

In western North America, snowpack supplies much of the water used for irrigation and for municipal and industrial uses, and snowmelt recharges groundwater and provides ecosystem-sustaining baseflow during low flow periods. Continued climate warming is expected to have large impacts on snowmelt hydrology, with subsequent impacts on low flows and snow and streamflow drought regimes. This research combined two separate methodologies, a data-driven (downward) approach and a process-based (upward) approach, to improve our understanding of snow drought and streamflow drought in the context of a warming climate. The data-driven approach combined observed hydroclimatic time series with multiple statistical methods, including bivariate and partial correlation and temporal and spatial analogs. The process-based approach combined climate change projections and hydrological modelling. The two approaches yielded consistent results that, together, illustrate that snow drought, low flows, and streamflow drought are sensitive to winter climate conditions, particularly precipitation and thawing degrees. In the context of climate warming, increased winter season thawing degrees leads to increased warm (temperature-driven) snow drought, shorter and less severe winter low flows, longer and more severe summer low flows, and increased summer streamflow drought risk. Further, both approaches showed that the response of snowmelt hydrology to climate warming is non-linear, and regions with winter temperatures near 0°C exhibit substantially larger impacts from +2°C of warming compared to regions with winter temperatures far below 0°C. Temperature-driven shifts in snow drought, low flows, and streamflow drought regimes will have widespread implications for surface water supply security. Increased frequency of warm snow droughts will likely lead to an increased frequency of mid-winter melt events, which will create challenges for water management. As summer low flow periods become more severe and snow-drought related summer streamflow droughts become more frequent, the potential for more severe summer water shortages increases. The most severe shortages will likely occur due to the co-occurrence of warm and dry conditions.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Diana Allen
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.