Estimates of lichen growth–rate in northern Sweden

Two lichenometric techniques were compared in a study of lichen growth–rate in northern Sweden. The first technique, based on the maximum lichen diameter on glacier moraines, was identical to the technique used in the 1970s, whereas the other utilized the lichen diameter measured on 100 randomly selected boulders. The results indicate that it does not matter which technique is chosen, as long as the technique is used consistently on both the calibration surfaces and the surfaces to be dated. The use of data from both the 1970s and the 2000s increased the number of calibration surfaces available. The new calibration curve indicates that the age of Little Ice Age moraines was underestimated by up to about 30 years in the study conducted in the 1970s.     

Learning about Feminism in Digital Spaces: online methodologies and participatory mapping

Collaborative online research offers opportunities and constraints for geographers. This article critically appraises a collaborative research process that we used to illuminate spatial and political dynamics of feminism contained within the online group ‘Destroy the Joint’ (DTJ). A mostly Australian initiative of over 74 000 Facebook members, DTJ aims to end sexism and misogyny in multiple ways. It operates as a meeting place, discussion forum, and umbrella organisation for numerous micro-campaigns that change in response to broader social, cultural and political contexts, and occur in online and offline spaces. We formed a collaborative research agreement with the moderators of DTJ to reflect on its work, asking participants to put themselves on a map and complete a survey. Participatory GIS and survey-based research operated in the real and the more-than-real spaces that contain paradoxical possibilities. We use the term more-than-real to highlight the excesses of digital spaces: the affect that social media generates, and is generated by, characterises the more-than-real, where extremes in productive and corrosive relations can permeate. Survey results showed diverse appreciations of DTJ's multiple activist tactics (across seemingly ‘superficial’ and ‘meaningful’ interventions), and creative ideas for future campaigns. Mapping revealed both dispersed networks and urban activist concentrations. Nevertheless, after an initial peak of interest and enthusiasm for reflecting on DTJ, the reporting back of research findings to DTJ followers did not garner significant interest. This article tracks that collaborative research trajectory. Intentions to build a hybrid research collective were not realised because of how the more-than-real affords possibilities and limitations. The politics of ‘giving-back’ within the more-than-real are critically engaged with in this appraisal of an experimental online collaboration.     

Internal architecture of a till sheet,Tiskilwa Formation,north‐central Illinois,USA: Application of architectural element analysis

Thick till sheets deposited during the Quaternary form significant aquitards in many areas of North America. However, the detailed sedimentary heterogeneity and architecture and depositional history of till units are not well understood. This study utilizes architectural element analysis to delineate the internal sedimentary architecture of the Tiskilwa Formation exposed at two outcrop sections in north‐central Illinois, USA. Architectural element analysis facilitates systematic delineation of sedimentary architecture based on the nature of facies contacts and change in facies associations, delineation of unit geometries and understanding of depositional processes at different scales of resolution; making architectural element analysis suitable for the sedimentological analysis and palaeoenvironmental reconstruction of subglacial deposits. Eleven facies types are identified in this study, including sand, gravel and diamict facies that record a suite of subglacial depositional processes. Detailed analysis of facies contacts (bounding surface hierarchy) and change in facies associations allows the delineation of five architectural elements, including coarse‐grained lens, coarse‐grained sheet, mixed zone, diamict lens and diamict sheet elements. The spatial arrangement and genetic interpretation of elements, and their spatial relationship with fifth‐order bounding surfaces, allows the delineation of five larger scale architectural units (‘element associations’), which can be mapped in the local study area and record at least three stacked successions of meltwater accumulation and till deposition. The results of this study can be utilized for architectural analysis of till sheets and provide insight to groundwater flow pathways through till in the study area and elsewhere.     

Inferring groundwater contributions and pathways to streamflow during snowmelt over multiple years in a discontinuous permafrost subarctic environment (Yukon, Canada)

Research on large northern rivers suggests that as permafrost thaws, deeper groundwater flowpaths become active, resulting in greater baseflow, increased concentrations of weathering ions and reduced concentrations of dissolved organic carbon in the streamflow. In contrast, at the headwater-catchment scale, where understanding of groundwater/surface-water interactions is developed, inter-annual variability in climate and hydrology result in complex hydrological and chemical responses to change. This paper reports on a 4-year runoff investigation in an alpine discontinuous permafrost environment in Yukon, Canada, using stable isotopes, major dissolved ions and hydrometric data, to provide enhanced insight into the inter-annual-variability runoff-generation processes. Stable isotope results suggest that pre-event (old) water stored within the catchment dominates the snowmelt hydrograph, and dissolved ion results reveal that groundwater pathways occur predominantly in the near-surface during freshet. Dissolved organic carbon varies inter-annually, reflecting changing melt patterns, whereas weathering ions generated from deeper flowpaths become diluted. The total snow-water equivalent does not have a major influence on the fraction of snowmelt water reaching the stream or the runoff ratio. Results from multiple years highlight the considerable variability over short time scales, limiting our ability to detect climate-change influences on groundwater at the headwater scale.     

The geomorphic character and hydrological function of an upland swamp,Budderoo plateau,southern highlands,NSW, Australia

Upland swamps are a form of topogenous mire that occur on the plateau areas of eastern Australia. These systems are well recognized for their ecological value, but little is known about their internal hydrological function and how this relates to their geomorphic structure and evolution. In this study, the geomorphic, sedimentological, and hydrological properties of an intact upland swamp on the Budderoo Plateau NSW are investigated. The geomorphic structure of the swamp is simple, and the sedimentology comprises basal layers of coarse sands, overlain by several layers of organic accumulation up to 3.3?m in thickness. Each of these sedimentary units has different hydrological behaviors (rates of water throughflow and discharge) that drive the overall function of the swamp in response to rainfall of various magnitudes and duration. Four hydrological response types have been identified in the functioning of this swamp. These response types (RT) are characterized by different peaks and recession responses to rainfall. The form of the hydrograph produced is controlled by antecedent water table position and the amount, timing and duration of rainfall. Depending on antecedent moisture conditions, the swamp can operate either as a store for water or as a rapid conduit for water throughflow and overland flow.     

The dust trail of Comet 67P/Churyumov-Gerasimenko between 2004 and 2006

We report on observations of the dust trail of Comet 67P/Churyumov-Gerasimenko (CG) in visible light with the Wide Field Imager at the ESO/MPG 2.2 m telescope at 4.7 AU before aphelion, and at with the MIPS instrument on board the Spitzer Space Telescope at 5.7 AU both before and after aphelion. The comet did not appear to be active during our observations. Our images probe large dust grains emitted from the comet that have a radiation pressure parameter β<0.01. We compare our observations with simulated images generated with a dynamical model of the cometary dust environment and constrain the emission speeds, size distribution, production rate and geometric albedo of the dust. We achieve the best fit to our data with a differential size distribution exponent of −4.1, and emission speeds for a β=0.01 particle of 25 m/s at perihelion and 2 m/s at 3 AU. The dust production rate in our model is on the order of 1000 kg/s at perihelion and 1 kg/s at 3 AU, and we require a dust geometric albedo between 0.022 and 0.044. The production rates of large (>) particles required to reproduce the brightness of the trail are sufficient to also account for the coma brightness observed while the comet was inside 3 AU, and we infer that the cross-section in the coma of CG may be dominated by grains of the order of .     

Military pollution and natural purity: seeing nature and knowing contamination in Vieques, Puerto Rico

Military activities have produced contaminated environments at many sites around the world. This contamination and the associated health risks play a large role in how these places can be redeveloped after military use. In this essay we focus on the island of Vieques, Puerto Rico which was used as a bombing range by the US military for six decades until 2003. We examine the ways different groups of people perceive this formerly militarized landscape and the ways that these perceptions legitimatize certain redevelopment options over others. Through participant observation, semi-structured interviews and an analysis of textual materials we found that many local residents view the island as suffering from severe contamination while the large number of visitors, tourism promoters and North Americans now flocking to the post-militarized Vieques view it quite differently. These perceptions of purity and contamination, affected by different knowledges of the island’s history, have led to differing valuation of the landscape and contentious economic, political, and cultural battles over an island often labeled “natural” despite a history of military use and social exclusion.

A Comparison of Awareness,Attitudes, and Usage of Water Quality Conservation Practices Between Amish and Non-Amish Farmers

This study provides a unique examination of Amish farmers’ awareness of water quality issues and their attitudes toward and use of agricultural conservation practices compared with small non-Amish farmers in Northeastern Indiana. There is minimal research about the conservation beliefs and behaviors of this growing and highly diverse ethnoreligious minority, who have faith-based technological restrictions and are often hesitant to work with community outsiders, especially the government. We find that, compared with non-Amish farmers, Amish farmers have limited awareness of the linkages between common agricultural practices and broader water quality problems and lower levels of adoption of conservation practices, with the exception of cover crops. This information is essential for conservation practitioners who need to work with a diverse range of agricultural producers to increase the uptake of conservation practices that address critical water quality concerns.     

Experimental study of bubble coalescence in rhyolitic and phonolitic melts

We have experimentally studied the process of bubble coalescence in rhyolite and phonolite melts of natural composition. The experiments involved decompression of water-saturated melts equilibrated at pressures and temperatures from 100 to 150 MPa and 775 to 840 °C in vertically oriented, rapid-quench capable, cold seal pressure vessels. One type of experiments (rhyolite MCR-100, 120, 150 and phonolite LSP-120 series') approximates a “static” bubble coalescence case, where we held the decompressed samples for ∼5 seconds to 4320 minutes (3 days) before quenching. The second type (rhyolite LPC-100 series) replicates an “expanding” bubble coalescence environment, where we continually decompressed the experiments at a rate of 0.5 MPa/s, examining samples quenched at ending pressures between 10 and 80 MPa. Our “static” case (MCR-100, 120, and 150, and LSP-120) results show significant increases in the modal bubble sizes and in the sizes of the largest bubbles, corresponding to measurable broadening in the size distributions. Their bubble number densities (N_V) decrease as a function of hold time at their final pressures (P_F), and can be fit well by power law functions. Our “expanding” case experiments (LPC-100) show a significant drop in N_V during the duration of the experiments that can be fit by an exponential equation as N_V vs. either time or P_F. Average estimates of bulk coalescence rates indicate a ∼1 order of magnitude drop in N_V for “static” case rhyolites in a 2-3 day period, and ∼2 orders of magnitude for phonolites within a 3 day period. Despite a ∼2 order of magnitude difference in viscosity, coalescene in the phonolite is only slightly faster than the rhyolite. The “expanding” case experiments show a ∼1 order of magnitude drop in N_V over 180 seconds. Thus, N_V's decrease 4 orders of magnitude faster in expanding vs. static bubbly rhyolite melts. Our results imply that significant bubble coalescence can occur in rhyolite magmas at relatively fast (∼20 m/s) ascent rates in the conduit. Thus, bubble interconnectivity, leading to high permeability, is possible during ascent. Bubble coalescence may occur during second boiling in magma bodies that are stalled in the crust. The timescales over which this occurs is much faster than the estimated rise rates for bubbles to reach the top of the magma chamber.