Re‐orientation of the extension direction and pure extensional faulting at oblique rift margins: comparison between the Main Ethiopian Rift and laboratory experiments

In this study, we draw on a unique combination of well‐resolved fault‐slip data and earthquake focal mechanisms to constrain spatial variations in style of faulting in the obliquely extending Main Ethiopian Rift, East Africa. These data show that both boundary and internal faults – oblique and orthogonal to the plate divergence (PD) respectively – exhibit almost pure dip‐slip motion, and indicate significant local deflection in orientation of the extension direction at rift margins. Scaled analogue models closely replicate the multidisciplinary observations from the rift and suggest that the process is controlled by the presence of a deep‐seated, pre‐existing weakness – oblique to the direction of PD – that is able to cause a local rotation in the orientation of the extension direction at rift margins. Minor counterclockwise block rotations are required to accommodate the difference in slip direction along the different fault systems, as supported by existing and new palaeomagnetic data from the rift.     

Effect of aerosol pollution on clouds and its dependence on precipitation intensity

In this study, simulations performed with a large-eddy resolving numerical model are used to examine the effect of aerosol on cumulus clouds, and how this effect varies with precipitation intensity. By systematically varying the surface moisture fluxes, the modeled precipitation rate is forced to change from weak to strong intensity. For each of these intensities, simulations of a high-aerosol case (a polluted case with a higher aerosol concentration) and a low-aerosol case (a clean case with a lower aerosol concentration) are performed. Whether or not precipitation and associated sub-cloud evaporation and convective available potential energy (CAPE) are large, liquid–water path (LWP) is larger in the high-aerosol case than in the low-aerosol case over the first two-thirds of the entire simulation period. In weak precipitation cases, reduction in aerosol content leads to changes in CAPE in the middle parts of cloud layers, which in turn induces larger LWP in the low-aerosol case over the last third of the simulation period. With strong precipitation, stronger stabilization of the sub-cloud layers in the low-aerosol case counters the CAPE changes in the middle parts of cloud layers, inducing smaller LWP in the low-aerosol case over the last third of the simulation period. The results highlight an interaction between aerosol effects on CAPE above cloud base and those in sub-cloud layers, and indicate the importance of a consideration of aerosol effects on CAPE above cloud base as well as those in sub-cloud layers. In the high-aerosol case, near the beginning of the simulation period, larger environmental CAPE does not necessarily lead to larger in-cloud CAPE and associated larger cloud intensity because aerosol-induced increase in cloud population enhances competition among clouds for the environmental CAPE. This demonstrates the importance of the consideration of cloud population for an improved parameterization of convective clouds in climate models.     

Engineering geomorphological interpretation of the Mitchell Creek Landslide,British Columbia,Canada

The recent assessment of the Mitchell Creek Landslide (MCL) in northern British Columbia is a good case history of engineering geomorphological analysis of a large landslide. It was completed using historic aerial photographs, with approximately 20-year time intervals dating back to the mid-twentieth century and field investigations completed between 2008 and 2014. The large bedrock slide initiated between 1956 and 1972 and continues to experience ongoing annual movements. Significant glacial downwasting and retreat has been observed in the photographic record, and it is hypothesized that alpine glaciation has contributed to development of the MCL. This paper documents four aspects of the engineering geomorphological assessment completed at the MCL: (i) topographic evolution, (ii) slope morphology, (iii) deformation features, and (iv) displacement behavior. Four distinct geomorphic zones have been defined at the MCL based on these analyses, controlled by different failure mechanisms. The extents of these zones have changed little over the documented history of the landslide, and rates of movement estimated from aerial photography have been consistent over the last 60 years. Retreat of the Mitchell Valley Glacier appears to have played an important role in landslide initiation, as the ice mass receded the kinematic freedom of the slope increased. This study of the initiation and development of the MCL demonstrates the capabilities of a multi-faceted approach to engineering geomorphology. The combination of historical aerial photographs with digital photogrammetric modeling and point cloud analysis techniques, and geomorphological mapping, allows for development of a robust understanding of landslide behavior.     

The Development of a Web‐based Demographic Data Extraction Tool for Population Monitoring

The Internet contains a great wealth of information available online. People search engines, such as WhitePages ( http://www.whitepages.com ), gather personal‐level demographic data, including full name, address, age and household members. Requiring only a surname and locational reference (e.g. city or postal code) as the minimum search criteria, such people search engines can be perceived as a gigantic database of demographic records. The objective of this article is to outline the development of a web‐based demographic data extraction tool for population monitoring. In this study, a web prototype was developed to extract web demographics of the Vietnamese‐American (VA) population in Texas, an ethnic minority with unique migration history, from WhitePages. After post‐processing, the personal‐level demographic data represent 40.3% of 202,003 VA in Texas reported by the American Community Survey (ACS) 2009. While all enumeration strategies, the web approach included, have their own strengths and weaknesses, this study suggests an alternative approach that is complementary to existing enumeration strategies. More research and development are needed to validate the accuracy of web demographics and further enhance data navigation and extraction rules. The utilization and release of web demographics must be cautious with regards to privacy and integrity of personal identity.     

Sampling oxygenated Archean hydrosphere: Implications from fractionations of Th/U and Ce/Ce* in hydrothermally altered volcanic sequences

Hydrothermally altered Archean igneous suites erupted in the submarine environment record variable excursions of Ce/Ce* and Th/U from primary magmatic values of 1 and ~ 4 respectively. Rhyolites of the 2.96 Ga bimodal basalt–rhyolite sequence of the Murchison Domain, Yilgarn Craton, Western Australia, hosting the Golden Grove VMS deposit, are enriched in MnO up to ten fold over primary values. Th/U ratios span 2.6–4.7, Ce/Ce* = 2.5–16, and Eu/Eu* = 1.3–3. The 2.8 Ga Lady Alma ultramafic–mafic subvolcanic complex of the same domain features highly dispersed MREE and LREE due to intense hydrothermal alteration. Th/U ratios span 0.005–0.16 from preferential addition of U, with Ce/Ce* = 0.6–2.2, and Eu/Eu* = 1–1.4. The eastern Dharwar Craton, India, includes greenstone terranes dominantly 2.7–2.6 Ga. Adakites of the Gadwal terrane preserve near primary magmatic Th/U, Ce/Ce*, and Eu/Eu*. In contrast, igneous lithologies of the Hutti greenstone terrane are characterized by total ranges of Th/U = 2–5.8, Ce/Ce* = 1.01–1.28, and Eu/Eu* = 0.82–1.26, and counterparts of the Sandur terrane have Th/U = 0.4–6.0, Ce/Ce* = 0.9–1.25, and Eu/Eu* = 0.8–1.8. Coexistence of Ce and Eu anomalies may reflect a two-stage process: low-temperature hydrothermal alteration at high water–rock ratios by oxidizing fluids, with evolution of the hydrothermal systems to high temperature, low water–rock ratios, under reducing conditions. Uranium is dominantly added to these lithologies over Th in common with Recent altered ocean crust. Iron-rich shales in the Sandur terrane record U-enrichment where Th/U = 2–4. Three shales record true negative Ce anomalies and Eu/Eu* = 0.8–2.4: true negative Ce anomalies, present in some other Archean iron formations, are interpreted as a signature of precipitates from the ocean water column whereas Eu anomalies are hydrothermal in origin. Volcanic flows of the 2.7 Ga Blake River Group, Abitibi greenstone terrane, Canada, preserve Th/U = 1.5–8.5, the conjunction of low Th/U values with Ce/Ce* = 1.4 in two samples, and Eu/Eu* = 0.15–1.3. Mobility of U and Ce in these hydrothermally altered Archean lithologies is in common with their mobility in Phanerozoic counterparts by oxygenated fluids.     

The concept of "sustainable ecological succession"; and its value in assessing the recovery of sediment seabed biodiversity from environmental impact

The problem of determining whether the biodiversity of an impacted muddy seabed is recovering can be resolved by drawing on a concept termed "sustainable ecological succession". At a site impacted by discharge of mine tailings, a suite of approximately 6 primary opportunist species (mostly polychaete worms) had started to sustain itself within 1-2 years after discharge ceased (1995), within the mix of 100+ other species which were not sustaining themselves. The start of a sustaining ecological succession is easily measurable by repeat surveys, and requires only the services of one taxonomic identifier to demonstrate the consistent presence and numbers of a limited range of species. At the assessed site, by 2000, some secondary opportunist species had entered the succession, and the species richness of the impacted area had come to equal that of the reference areas.     

Arctic microbial ecosystems and impacts of extreme warming during the International Polar Year

As a contribution to the International Polar Year program MERGE (Microbiological and Ecological Responses to Global Environmental change in polar regions), studies were conducted on the terrestrial and aquatic microbial ecosystems of northern Canada (details at: http://www.cen.ulaval.ca/merge/). The habitats included permafrost soils, saline coldwater springs, supraglacial lakes on ice shelves, epishelf lakes in fjords, deep meromictic lakes, and shallow lakes, ponds and streams. Microbiological samples from each habitat were analysed by HPLC pigment assays, light and fluorescence microscopy, and DNA sequencing. The results show a remarkably diverse microflora of viruses, Archaea (including ammonium oxidisers and methanotrophs), Bacteria (including filamentous sulfur-oxidisers in a saline spring and benthic mats of Cyanobacteria in many waterbodies), and protists (including microbial eukaryotes in snowbanks and ciliates in ice-dammed lakes). In summer 2008, we recorded extreme warming at Ward Hunt Island and vicinity, the northern limit of the Canadian high Arctic, with air temperatures up to 20.5 °C. This was accompanied by pronounced changes in microbial habitats: deepening of the permafrost active layer; loss of perennial lake ice and sea ice; loss of ice-dammed freshwater lakes; and 23% loss of total ice shelf area, including complete break-up and loss of the Markham Ice Shelf cryo-ecosystem. These observations underscore the vulnerability of Arctic microbial ecosystems to ongoing climate change.