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

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Stability and mechanism of failure of The Barrier, southwest British Columbia

Author: 
Date created: 
2011-04-21
Abstract: 

The Barrier is a steep, 250 m-high escarpment of dacite in Garibaldi Provincial Park, British Columbia. The lava flow comprises four lobes, two of which (Lobes 3 and 4) came into contact with the late Pleistocene Cordilleran ice sheet. Lobe 3 was the source of a major landslide in 1855-1856 and a smaller event in 1977. This thesis investigates potential mechanisms responsible for landslides from The Barrier. Methods that I applied include magnetic surveys to determine the three-dimensional character of lava flows forming The Barrier, long-range photogrammetry to map the structure of the escarpment in digital terrain models, field mapping, distinct element modelling, and passive seismic landslide monitoring. Of particular importance to the stability of The Barrier are ice-contact structures in the volcanic rocks, which provide clues about emplacement environments. Results show that The Barrier should be considered potentially unstable and that past instability is intimately linked to structures produced by emplacement of the lavas against glacier ice. My work also provides new geophysical and geomechanical data for The Barrier.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. John J. Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Rock avalanches on glaciers

Author: 
Date created: 
2011-04-14
Abstract: 

This thesis examines relations between rock avalanches and the glaciers on which they are deposited. I have attempted to understand a geophysical phenomenon from two viewpoints: sedimentology and glaciology. The contributions are both methodological, and practical. I have used a GIS to quantify debris sheet geomorphology. A thorough characterization of rock avalanche debris is a necessary step in understanding the flow mechanics of large landslide. I have also developed a technique for solving radar interferometry phase unwrapping problems. A digital elevation model created using this technique is used to quantify the velocity of a glacier prior to its disturbance by landslides. Three debris sheets on Black Rapids Glacier, Alaska, have coarse blocky rims. Longitudinal flowbands in these debris sheets, as well as in a debris sheet deposited on Sherman Glacier, Alaska, separate bands of different block size. Elongated blocks are parallel to flow, except at the perimeter of the debris sheets, where they are aligned nearly perpendicular to flow. Blocks on Sherman Glacier have been reoriented by glacier flow since the landslide in 1964. The matrix of all four debris sheets does not systematically change with depth or distance from the source. However, Sherman Glacier debris has become coarser due to weathering. Black Rapids Glacier surged in 1936-1937. Between 1949 and 1995, the glacier gradually returned to a pre-surge hypsometry. Maximum elevation changes along the glacier centerline in the ablation and accumulation areas, are, respectively, -249 m (-5.4 m a-1) and +63 m (+1.4 m a-1). Centerline thickening of +62 m (+1.4 m a-1), just above the Loket tributary in the upper part of the ablation zone, indicates dynamic thickening following the surge. The response of Black Rapids Glacier to the rock avalanches is spatially and temporally complex. Increases in measured and modelled surface velocity across the debris sheets are much greater than velocities observed higher on the glacier. The velocity recorded at the downglacier margin of the debris doubled between 2002 and 2004, resulting in a reversed velocity gradient. The changes in ice dynamics are related to the landslides through the effect of debris insulation on mass balance.

Document type: 
Thesis
File(s): 
Senior supervisor: 
John J. Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Quaternary geology of Bluegoose Prairie, Baffin Island, Nunavut

Date created: 
2011-04-13
Abstract: 

The surficial geology and glacial history of Bluegoose Prairie (NTS 36H/1-8) are described, and the first surficial geology map of the area is presented. Four phases of ice flow occurred in Bluegoose Prairie since the Last Glacial Maximum. Collapse of the Foxe Dome ca. 6.2 - 6.5 14C ka BP initiated deglaciation of Foxe Basin. Deglaciation of Bluegoose Prairie and subsequent isostatic rebound were rapid, as evidenced by a relative sea level curve constructed using marine mollusc 14C ages. Diverse macrofossil assemblages show deglacial climate was as warmer or warmer than today. Contemporaneous pairs of terrestrial and marine macrofossils allow for the measurement of deglacial marine reservoir age for Bluegoose Prairie. This new value of 985 ± 10 14C years, 265 14C years older than previously thought, can be applied to deglacial marine 14C ages in Foxe Basin and Hudson Strait. Application of this value allows more accurate palaeogeographic reconstructions.

Document type: 
Thesis
Senior supervisor: 
Dr. Brent Ward
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

An integrated approach to estimating groundwater recharge and storage variability in southern Mali, Africa

Author: 
Date created: 
2011-06-10
Abstract: 

Groundwater recharge in southern Mali is investigated using a variety of methods. The aquifer system comprises a surficial unconfined aquifer in laterite that is hydraulically connected by vertical fractures through a sedimentary rock layer to a deep fractured semi-confined aquifer. Observed groundwater storage fluctuations from historical water level data correlate with GRACE satellite terrestrial water storage (TWS) variations, with peaks in September and lows in May; however, soil-moisture corrected GRACE data peaked in November due to the GLDAS model poorly predicting the timing of soil-water storage changes. Recharge modeling using HELP gave an average annual net recharge of 132.2 mm (12.6% of rainfall), comparing well with estimates from historical water level (149.1 mm; 16.4%) and GRACE (149.7 mm; 14.8%) data. Major ion chemistry suggests groundwater is fresh (average TDS of 205 mg/L) and rapidly recharged. 18O and 2H concentrations in groundwater and precipitation indicate July-September rainfall as the recharge source.

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

Characterizing highwall slopes at the Line Creek Mine, British Columbia using terrestrial photogrammetry

Author: 
Date created: 
2011-06-13
Abstract: 

Characterization of pit wall stability requires an understanding of the role of structural geology (folds, faults and jointing) in both providing information on kinematic release and as a control on rock mass quality. This thesis discusses the application of digital photogrammetry in the mapping of highwall structures within two pits at the Line Creek Coal Mine. The photogrammetric data are used to characterize fold type, geometry and attitude using classical structural geology techniques. Detailed discontinuity mapping using digital terrain models created from photogrammetric software allows measurement of orientation, trace length and spacing for different discontinuity sets. Kinematic and limit equilibrium analyses indicate that bench-scale failures and rockfall are mainly structurally controlled at Line Creek. The variation of debris height on benches, loss of bench width and variation in rockfall size can all be determined from digital terrain models and used to assess pit wall stability.

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

Hydrogeochemical evolution and arsenic mobilization in confined aquifers formed within glaciomarine sediments

Date created: 
2011-06-06
Abstract: 

The hydrogeochemical evolution and arsenic mobilization mechanisms in groundwater occurring in confined aquifers formed within glaciomarine sediments in the Lower Fraser Valley, British Columbia, are addressed. Methodology includes analysis of chemical and isotopic composition of groundwater, and mineralogical and chemical analysis of sediment samples sourced from core. Groundwater in confined aquifers is Na-HCO3 or Na-Cl type, basic and reduced; whereas groundwater in unconfined aquifers is Ca-Mg-HCO3 type, near neutral and oxidized. The chemistry of groundwater in confined aquifers is controlled by cation exchange, dissolution of carbonate minerals, silicate mineral weathering, and mixing with saline connate water suggesting freshening conditions. Arsenic release occurs as groundwater flows through glaciomarine sediments; its mobility is favoured by basic pH and reducing groundwater conditions. Possible arsenic release mechanisms are iron oxides reduction and sulphides oxidation. A method of spatially representing likelihood of arsenic occurrence in groundwater based on geochemical interpretation and available data is presented.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dirk Kirste
Diana Allen
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

An integrated study of deep-seated gravitational slope deformations at Handcar Peak, southwestern British Columbia

Date created: 
2011-03-24
Abstract: 

I propose an integrated methodology for the study of deep-seated gravitational slope deformation (DSGSD) and apply the methodology to a gravitationally deforming slope at Handcar Peak in southwestern British Columbia. I mapped DSGSD-related geomorphologic features such as antislope scarps, trenches, ponds, rockslides, and rockfalls on aerial photographs and in the field, and conducted an investigation of sediments deposited behind an antislope scarp to determine the history of movement of the feature. I also characterized the structure and strength properties of the deforming rock mass through engineering geological mapping and investigated the mechanics of movement by kinematic analysis and distinct element numerical modelling. Results suggest that the current episode of movement at Handcar Peak began during or shortly after deglaciation and is continuing. Gravitational lineaments are the surface expression of displacement on weak fault planes. Deformation in numerical models is driven by slip on these faults and on downhill-dipping joints.

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

Tracking the evolution of magmatic volatiles from the mantle to the atmosphere using integrative geochemical and geophysical methods

Date created: 
2011-01-07
Abstract: 

This thesis characterizes the transfer of magmatic volatiles through the mantle and the crust to the atmosphere through the integration of melt inclusion data for pre-eruptive volatile contents with surface measurements of volcanic degassing (recorded in micro-gravity changes and volcanic fumarole and plume gas compositions) at two contrasting volcanoes: Sierra Negra, Galápagos Islands and Kawah Ijen, Indonesia. In particular, it explores the process of fluid transfer in the mantle, the partitioning of volatile elements during mantle melting and degassing of the magma through the crust, and the effect of near-surface (e.g., interactions with groundwater and hydrothermal fluids), and surface processes (e.g., cooling and mixing with air) on the gas species. The effects of differences in initial volatile content and internal volcano structure on the types of eruptions and emissions recorded at each volcano are also discussed. The comparison of Sierra Negra and Kawah Ijen volcanoes reveals that differences in style of volcanic activity are primarily a function of magmatic plumbing system as opposed to differences in initial volatile content. In both cases, permeability of the crust and degassing style have exerted a dominant control over the recent style of activity (last century). Recent eruptions at Sierra Negra are not necessarily associated with magma recharge into shallow reservoirs but can be caused by subtle changes in the pressure regime of a magma chamber, a process which is closely associated with degassing and system permeability. Large explosive eruptions at Kawah Ijen are currently impeded by the open system (permeable) flow of magma and gas through the plumbing system. Hydrothermal systems play an important role in controlling the permeability of a system and the composition of the gases measured at the surface. The comparison of theoretically modeled gas compositions with actual measured compositions is an effective approach to studying the influence of hydrothermal systems at open vent volcanoes.

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

Recent deglacierization of the upper Wheaton River Watershed, Yukon

Author: 
Date created: 
2010-11-08
Abstract: 

My research involves the study of Wheaton Glacier, the largest glacier in the Wheaton River watershed in southern Yukon Territory. Since the Little Ice Age, Wheaton Glacier has lost 50% of its area and 58% to 63% of its volume. Despite increasing winter snowfall, rising temperatures tied partially to negative PDO phase changes continue to drive the persistent negative mass balance of the glacier. Periglacial activity, extreme precipitation events and glacier recession are altering sediment delivery in the upper Wheaton River watershed. Sediment is moving downstream from the Wheaton Glacier forefield and large, out-of-channel debris flows are affecting the fan at the mouth of the valley. Evidence from sediment cores collected on the distal part of the fan suggests that debris flows have dominated sedimentation at the mouth of the valley during the last half of the Holocene, coincident with Neoglacial advances and the historic period of rapid glacier retreat.

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

Characterizing the plumbing systems of active volcanoes through potential field studies

Date created: 
2010-11-16
Abstract: 

The processes involved with mass transport through a volcanic plumbing system are poorly understood. Through the use of potential field studies, this thesis aims to identify volcanic structures, processes and Earth properties that control volcanic activity. Gravity and total magnetic surveys at Kĩlauea (Hawaii, USA), Masaya (Nicaragua) and South Sister (Oregon, USA) volcanoes, allowed for development of models to investigate magma transport at different spatial and temporal resolutions. At Kĩlauea rapid, short term mass flux perturbations were characterized within the shallow plumbing system and long term mass increases were inferred in the creation of a large intrusive complex. Constraints on crustal viscosity were obtained at South Sister through gravity and deformation models. At Masaya, constraints were obtained for void space in the active crater and shallow geologic properties. Potential field studies at active volcanoes can clearly bring insight into the fundamental processes of magma transport and emplacement.

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