Occurrence and geotechnical properties of loess in Canada

Sweeney, S.J. and Smalley, I.J., 1988. Occurrence and geotechnical properties of loess in Canada. Eng. Geol., 25: 123–134.

There are modest amounts of loess in Canada. As in most of North America it is probably produced by a combination of glacial grinding and cold weathering. Atterberg limits of Canadian loess are comparable with reference samples from the U.S.A. A deposit at Kamloops in British Columbia suffers a 15% linear collapse when loaded and wetted. Earlier estimates that the deposit was more than 100 m thick are probably in error; only the top part of the sedimentary deposit is loess.     

Some constraints on the formation of the Zambian Copperbelt deposits

The origin of the ores of the Zambian Copperbelt are examined by referring to the timing and physicochemical conditions of the formation of the orebodies and by reviewing the possible sources of Cu and Co available. The constraints imposed by these two conditions leads to the conclusion that the ores were formed during early diagenesis, primarily by bacterial action on metal rich solutions derived from the pre-Katangan basement rocks.     

Sulfur dioxide emissions and degassing behavior of Erebus volcano,Antarctica

Emission rates of sulfur dioxide (SO₂) were measured at Erebus volcano, Antarctica in December between 1992 and 2005. Since 1992 SO₂ emissions rates are normally distributed with a mean of 61 ± 27 Mg d^− 1 (0.7 ± 0.3 kg s^− 1) (n = 8064). The emission rates vary over minutes, hours, days and years. Hourly and daily variations often show systematic and cyclic trends. Long-wavelength, large amplitude trends appear related to lava lake area and both are likely controlled by processes occurring at depth. Time series analysis of continuous sequences of measurements obtained over periods of several hours reveals periodicity in SO₂ output ranging from 10 to 360 min, with a 10 min cycle being the most dominant. Closed and open-system degassing models are considered to explain observed variable degassing rates. Closed-system degassing is possible as rheological stiffening and stick/slip may occur within the system. However, the timescales represented in these models do not fit observations made on Erebus. Open-system degassing and convection fits the observations collected as the presented models were developed for a system similar to Erebus in terms of degassing, eruptive activity and process repose time. We show that with the observed emission rate (0.71 kg s^− 1) and a crystal content of 30%, magma will cool 65 °C to match observed heat fluxes; this cooling is sufficient enough to drive convection.     

Modeling Coronal Loop Abundances: Effects of Parameter Variations on Observables

Coronal abundance variations arise from and affect solar atmospheric processes such as coronal heating and structural dynamics. Lenz (1999) presented initial results of a numerical theoretical study of abundances and ion heating rates in static, steady-state coronal loops. We present here a closer investigation of two fundamental aspects of the physics of coronal abundances, relating modeling parameters to observables: (1) the effect of varying the abundances on the electron temperature and (2) the effect of varying the ion heating rate on abundances.     

Hydro-Climatic Trends of the Yellow River Basin for the Last 50 Years

Kendall's test was used to analyze the hydro-climatic trends of the Yellow River over the last half century. The results show that: (1) the runoff of the basin has decreased even after allowing for human uses, (2) the watershed has become warmer with a more significant increase in minimum temperature than in mean and maximum temperatures, and (3) no significant change in precipitation trend was observed. The major reasons for these results include human activities, global warming, land use/land cover change, and others, such as accuracy of natural runoff estimation, precipitation characteristics, groundwater exploitation, water transfer, and snowmelt. Homogeneity analysis indicated that precipitation, temperature, maximum temperature, and minimum temperature were all heterogeneous and the trends varied from region to region and from month to month. If the Intergovernmental Panel on Climate Change (IPCC) projections of continued warming in the region during the 21st century are correct, the present results then suggest that the trend towards reduced runoff is likely to lead to exacerbated problems for agriculture, industry, urban communities, and the overall regional environment.     

Tectonometamorphic evolution of the tip of the Himalayan metamorphic core in the Jajarkot klippe,west Nepal

New phase equilibrium modelling, combined with U–Th/Pb petrochronology on monazite and xenotime, and ⁴⁰Ar/³⁹Ar geochronology on white mica, reveal the style of deformation and metamorphism near the southern tip of the extruded Himalayan metamorphic core (HMC). In the Jajarkot klippe, west Nepal foreland, greenschist to lower amphibolite facies metamorphism is entirely constrained to the Cenozoic Himalayan orogeny, in contrast with findings from other foreland klippen in the central Himalaya. HMC rocks exposed in the Jajarkot klippe yield short‐lived, hairpin pressure–temperature–time–deformation paths that peaked at 550–600°C and 750–1,200 MPa at 25 Ma. The Main Central thrust (MCT) and the South Tibetan detachment (STD) bound the base and the top of the HMC, respectively, and were active simultaneously for at least part of their deformation history. The STD was active at c. 27–26 Ma and possibly as late as c. 19 Ma, while the MCT may have been active as early as 27 Ma and was still active at c. 22 Ma. The tectonometamorphic conditions in the Jajarkot klippe are characteristic of crustal thickening and footwall accretion of new material at the tip of the extruding metamorphic orogenic core. Our new results reveal that collisional processes active in the middle to late Miocene at the base of the HMC now exposed in the hinterland were also active earlier, during the Oligocene, at the tip of the southward‐extruding middle crust.     

Digital Data-Centric Geography: Implications for Geography's Frontier

The debate regarding geographic information systems (GIS) as tool, toolbox, or science still lingers in geography departments and among geographers. Analysis of geographic information is a vital component of decision making among business, governments, researchers, and academics. GIS users, geographers and nongeographers alike, use and benefit from problem-solving methods in numerous fields and contexts, making the use of GIS and the core competencies associated with using GIS a topic of intense debate. Complicating this ongoing discussion is the rise of data-centric approaches to research in geography that further expand the capabilities of spatial analysis and add to the expected knowledge of a GIS user and analyst. Building on a panel discussion at the 2016 American Association of Geographers (AAG) annual meeting, as well as informal dialogues on Twitter and other social media platforms that navigate this issue in academics and industry, this article explores how skills in research computing and programming operate in geography and GIS, especially given the rise of data-centric approaches to research in these realms. Some topics, like the costs and benefits of open and closed source software, are familiar from previous discussions in geography and GIS. Others, though, like the reward structures and recognition for computing skills or programming ability, have not been widely considered given the current landscape.