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Earthquakes in western Quebec and southern Ontario present a major contribution to the natural hazards in south eastern Canada due to their proximity to major population centres. However, the seismic characteristics of the events in these regions have not been well documented. Improved knowledge of earthquake distribution and seismic controlling mechanisms provides a great benefit for earthquake hazard analysis in eastern Canada. The available information about the tectonic stress indicators, including focal mechanisms, was compiled for Canada prior to 1994. The present research is concentrated mainly on determination of the focal mechanisms and hypocentre locations of the earthquakes after 1993 with M > 3.5 to characterize the present-day regional and local stress fields in southern Ontario and western Quebec. An attempt was also made to differentiate local zones with comparatively homogeneous tectonic stresses orientation and seismic regimes, thus providing information for future re-assessment of the seismic hazard in each region. Considering seismic parameters such as the trend of the epicentres, focal depths and the state of stress of the events along with their tectonic settings, ten distinct clusters have been proposed for western Quebec and two clusters of events were determined for southern Ontario with comparatively consistent focal mechanisms. The locations and characteristics of seismicity clusters appear to be consistent with the hypothesis that they are near the locations of large historic and prehistoric events, and represent exceptionally persistent aftershocks of past large earthquakes. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-06-15 19:46:15.691

Thesis (Ed. D.)--University of Kentucky, 1992. / Abstract ([2] leaves) bound with copy. Vita. Includes bibliographical references (leaves 145-162).

This thesis investigates igneous rocks from northwestern Graham Land, Antarctic Peninsula, in terms of their chemistry and timing of magmatism. In northwestern Graham Land, plutonic and hypabyssal rocks of the Antarctic Peninsula batholith and volcanic rocks of the Antarctic Peninsula Volcanic Group crop out in almost equal proportions. These igneous rocks intrude and unconformably overlie low-grade metasedimentary 'basement' of the Trinity Peninsula Group (?Carboniferous to Triassic). The Mesozoic to Cenozoic subduction-related plutonic rocks range from gabbro to granite, with granodioritic compositions predominating. Mafic to intermediate hypabyssal intrusions cutting the plutonic, volcanic and 'basement' rocks are common. Major and trace element data, as well as petrographical data, from igneous rocks of the Danco Coast and Palmer Archipelago indicate a 'normal' calc-alkaline suite typical of active continental margins. Fractional crystallisation of a mafic parental magma seems to be the dominant process responsible for the range of igneous lithologies observed in the study area.

Geotourism is becoming more popular and can play a critical role in creating literacy in communities. Moreover, the Big Ideas of the Earth Science Literacy Initiative can be used within signage to address literacy. Because all citizens should have a basic knowledge of Earth Science in order to make informed decisions that relate to Earth Science, geotourism can be used as a way to increase Earth Science knowledge, along with other positive outcomes related to communities' increased well-being. A careful investigation of N=59 geosites reveals that signage can be used to increase this knowledge but that there is a deficit in the number and quality of the signage present at some of these sites. A gap has been uncovered regarding the efforts to teach Earth Science

The aeolian threshold condition is identified as defining the critical state between a static sediment bed and active aeolian transport. Disparities in reported mean threshold shear velocities (U*T) are attributed to variation in: (a) flow regimes; (b) entrainment criteria; (c) particle characteristics and exposures; and (d) techniques for measurement of 1*T The relative significance of these factors is assessed for strips and beds of ballotini, aeolian sand, salt crystals and sugar crystals using the controlled, reproducible flow conditions of the developing boundary layer over a flat plate. Such a plate was covered with a non-erosive layer of grains to simulate a flat sediment bed and was positioned in a wind tunnel. values were calculated using the momentum integral method. In a separate study, threshold conditions on impervious and permeable beds were compared directly. Analysis of entrainment from strips and beds on the plate shows that the threshold condition is principally determined by a critical degree of overlap between the probability distributions of local shear velocity, P ( U ), and of grain threshold shear velocity, P(U*T). Characteristic P(U*T) distributions for test materials were determined and two objective definitions of U*T were devised. Experimental *T values agree well with published data and are used to resolve the data scatter associated with both 'restricted' and 'universal' threshold curves. Rates of aeolian entrainment over a range of values are found to be an inverse exponential function of time and wind speed. Different erosion rates were found to result from skewness of P(U) and degree of overlap between P(U) and P(U*T). Fluid sweeps in the turbulent bursting cycle are considered to be the primary entrainment mechanism. Medium/high-speed cine film gave insight into initiation processes. Grain oscillation due to vortex shedding and initial motion characterized by a progressive rolling and bouncing were observed. Bed permeability was not found to affect aeolian threshold values.

<p>The Grenville Province is alGa orogenic belt, composed of much older terranes whose age and extent require mapping in order to gain a better understanding of its geological evolution. Manicouagan, Quebec, in the Grenville Province, has experienced several orogenic events, as well as being the site of a 214 Ma hypervelocity impact event, which has further complicated its geological structure. By analyzing surface samples from this area, as well as driB core of the country rocks involved in the impact, the original age of crustal formation for the various terranes can be calculated, thus revealing the evolutionary history of the Manicouagan area.</p> <p>Nd isotopes are resistant to metamorphic disturbances, therefore permitting accurate calculations of original crustal formation ages. Nd-isotopic analysis of granitoid orthogneisses, has identified three major crustal formation age groups in the area. These are: Mesoproterozoic (1.58 Ga), Paleoproterozoic (1.86 Ga), and Archean (2.8 Ga). These average depleted mantle model ages (TOM) correspond well with isochron reference lines, supporting their validity as actual geologic events.</p> <p>The spatial distribution of age data results indicate that the Archean basement extends farther south on the western side of the Manicouagan reservoir than previously thought, whereas the eastern side is dominated by Paleoproterozoic crust. In contrast, the Manicouagan Imbricate Zone (MIZ), located between the Archean and Paleoproterozoic crustal terranes, as a wider scatter of Nd data attributed to mixing between Archean and Proterozoic sources. This crustal terrane has been limited to within the interior of the reservoir in the south, and extends just north of the reservoir. The location of the boundary between the Archean and Paleoproterozoic terranes, the Allochthon Boundary Thrust (ABT), was largely agreed upon to the east and west of the impact, but its position was highly ambiguous near the impact itself. New Nd analysis shows that this boundary crosses onto the island on the NW side of the reservoir, and exits to the west of the previously established Cryptic Shear Zone (CSZ) at the southern end of the impact. The boundaries of these distinctive crustal terranes are further supported through aeromagnetic evidence.</p> <p>The 214 Ma hypervelocity event resulted in the instantaneous melting of target rocks located beneath the impact. Isotopic and elemental geochemistry was employed to characterize the composition of the meltsheet. These data show that the melt sheet was largely derived from the MIZ, but cannot rule out a small component of underlying Archean crust. Further isotopic, trace element and major elemental analyses are needed in order to fully decipher the target rock composition.</p> / Master of Science (MS)

Primary succession on the basaltic lava flows of Mt. Etna was studied usmg chronosequence theory to investigate the first 500 years of ecosystem development. Separate experiments were conducted to look at how plant species, nutrient availability and lichen activity on the lava changed over time under different conditions based on the site location (age, aspect and altitude on the volcano). By comparing the results of these different areas of study, close links were observed between soil development and nutrient availability. Lichens were found to be an important stage in primary succession introducing biomass to form a developing soil as well as weathering the lava surface. The plant species present on the lava were found to change as plants first colonised the lava and were then replaced as further species appeared over time. Nutrient availability was investigated in living plant material by measurement of the enzyme nitrate reductase and also in the developing soil. Two large inputs of nitrogen were observed in the chronosequences. An early input believed to be lichen derived and another steadily increasing input associated with the soil. The biomass of the nitrogen fixing lichen Stereocaulofl vesuvianum on the lava flows was found to change over time with a rapid increase over the first 100 years of the chronosequence followed by a slower decline as competition and shading from vascular plants covered available habitat. S. vesuvianum was also found to be an efficient weathering agent on the lava altering the surface morphology. This weathering was observed qualitatively by detailed visual examination of the lava surface by scanning electron microscopy. Weathering was also measured quantitatively using an intelligent machine vision computer system, to collate the surface changes of many images simultaneously and compare surface change to a baseline chronosequence, allowing discrimination of fine differences in the extent of weathering. Two of the experiments conducted on Mt. Etna (nitrate reductase activity and lichen weathering) were repeated on a second volcano, Mauna Loa (Hawaii). This tested if the trends observed on Etna were typical of primary succession on lava and the impact of a different climate regime (tropical) compared to Etna (temperate). Nitrate reductase activity was found to be very low in the primary colonising species studied on Hawaii indicating that nitrogen is limited on the early lava flows. Lichen weathering by Stereocaulon vulcani on Hawaii was found to occur in a comparable manner to S. vesuvianum on Etna, and was similarly controlled by the lichen biomass and associated climatic conditions.