Teaching Geographical Information Handling Skills for Lower-income Countries

Geographical Information Systems are seen by many as a quick 'fix' for the problems of lower-income countries and people in those countries have been encouraged to adopt this perception, along with the technology. As teachers of students from LICs, we seek to avoid reproducing a contextless transfer of technical skills and rather aim to promote an education based on the limitations of the technology and on the nature and construction of information. While identifying GIS as one of many components of 'geographical information', we emphasise the importance of including 'non-GIS' staff in the education process. We advocate a 'problem-posing' approach to the teaching of 'Geographical Information for Development' and discuss some of the challenges which this raises, both for teachers and students.     

Characterization of the subsurface architecture and identification of potential groundwater paths in a clay-rich floodplain using multi-electrode resistivity imaging

The interaction between surface water and groundwater in clay-rich fluvial environments can be complex and is generally poorly understood. Airborne electromagnetic surveys are often used for characterizing regional groundwater systems, but they are constrained by the resolution of the method. A resistivity imaging survey has been carried out in the Macquarie Marshes (New South Wales, Australia) in combination with water chemical sampling. The results have enabled the identification of buried palaeochannels and the location of potential recharge points. The data have been compared with previously published airborne electromagnetic data in the same area. Deeper less conductive features suggest that there is a potential connection between the Great Artesian Basin and groundwater contained within the shallow sand aquifer. Even though the chemistry of the groundwater samples does not indicate interaction with the Great Artesian Basin, the observed discontinuity in the saprolite implies potential for this to happen in other locations.     

Faunal utilization of created intertidal eastern oyster (Crassostrea virginica) reefs in the southeastern United States

Oyster cultch was added to the lower intertidal marsh-sandflat fringe of three previously createdSpartina alterniflora salt marshes. Colonization of these created reefs by oysters and other select taxa was examined. Created reefs supported numerous oyster reef-associated faunas at equivalent or greater densities than adjacent natural reefs. Eastern oyster (Crassostrea virginica) settlement at one site of created reef exceeded that of the adjacent natural reefs within 9 mo of reef creation. After only 2 yr, harvestable-sizeC. virginica (>75 mm) were present in the created reefs along with substantial numbers ofC. virginica clusters. The created reefs also had a higher number of molluscan, fish, and decapod species than the adjacent natural reefs. After 2 yr the densities ofC. virginica, striped barnacle (Balanus amphitrite), scorched mussel (Brachidontes exustus), Atlantic ribbed mussel (Geukensia demissa), common mud crab (Panopeus herbstii), and flat mud crab (Eurypanopeus depressus) within the created reefs were equivalent to that of adjacent natural reefs. From these data it is evident that created oyster reefs can quickly acquire functional ecological attributes of their natural counterparts. Because the demand for oysters continues to increase in the face of dwindling natural resources, habitat creation techniques need to evolve and these approaches need to consider the ancillary ecological benefits reef creation may provide. Reef function as well as physical and ecological linkages of oyster reefs to other habitats (marsh, submerged aquatic vegetation, and bare bottom) should be considered when reefs are created in order to provide the best use of resources to maintain the integrity of estuarine systems.     

The Optical Properties of Greater Florida Bay: Implications for Seagrass Abundance

Water column optical properties of Greater Florida Bay were investigated in the context of their impacts on seagrass distribution. Scattering played an important role in light attenuation throughout the shallow water system. The northwest region was characterized by an absence of seagrasses and the highest scattering by particles, mostly from resuspended carbonate sediments. Higher seagrass densities were observed in the open waters just north of the Florida Keys, where absorption coefficients were dominated by colored dissolved organic material and scattering was lower than in the northwest region. Patchy dense seagrass meadows were observed in the clear waters south of the Keys where scattering and absorption were low and contributed equally to light attenuation. In general, seagrasses were observed in areas where >7.5% of surface irradiance reached the plants and where optical properties were not dominated by scattering. Although the prevention of eutrophication and nuisance algal blooms may be necessary for preserving seagrass meadows in this system, our observations and model calculations indicate that nutrient control alone may be insufficient to permit seagrass recolonization if optical properties are dominated by particulate scattering from resuspended sediments.     

Comparisons of high-frequency acoustic fluctuations with ocean-temperature and sea-surface fluctuations in shallow water

Dynamic ocean processes produce small thermal variations that induce spatial and temporal variability in the ocean's index of refraction and in the spatial scale along an acoustic propagation path. This paper reports measurements and analysis of thermal microstructure effects on ping-to-ping amplitude and phase variability of shallow-water direct-path acoustic propagation in the 20-200 kHz frequency range. These measurements were conducted during a joint experiment conducted by the Naval Research Laboratory and the North Atlantic Treaty Organization Supreme Allied Commander Atlantic (SACLANT) Undersea Research Centre, La Spezia, Italy, in 8 m of water off American Beach, located between Pisa and Livorno, Italy. Experimental observations are compared with predictions for isotropic and anisotropic turbulence, as well as for sea-surface swell. Measured phase and log-amplitude variances coincide with predictions and are relatively insensitive to weak water-column stability. The sea-surface swell dominates phase variances for this data and turbulence dominates log-amplitude variances. These results provide a reasonable lower limit on high-frequency ping-to-ping amplitude and on phase variability produced by benign shallow-water thermal fluctuations.     

Crystal structure, Raman and FTIR spectroscopy, and equations of state of OH-bearing MgSiO3 akimotoite

MgSiO₃ akimotoite is stable relative to majorite-garnet under low-temperature geotherms within steeply or rapidly subducting slabs. Two compositions of Mg–akimotoite were synthesized under similar conditions: Z674 (containing about 550 ppm wt H₂O) was synthesized at 22 GPa and 1,500 °C and SH1101 (nominally anhydrous) was synthesized at 22 GPa and 1,250 °C. Crystal structures of both samples differ significantly from previous studies to give slightly smaller Si sites and larger Mg sites. The bulk thermal expansion coefficients of Z674 are (153–839 K) of a ₁ = 20(3) × 10^?9 K^?2 and a ₀ = 17(2) × 10^?6 K^?1, with an average of α ₀ = 27.1(6) × 10^?6 K^?1. Compressibility at ambient temperature of Z674 was measured up to 34.6 GPa at Sector 13 (GSECARS) at Advanced Photon Source Argonne National Laboratory. The second-order Birch–Murnaghan equation of state (BM2 EoS) fitting yields: V ₀ = 263.7(2) Å³, K _T0 = 217(3) GPa (K′ fixed at 4). The anisotropies of axial thermal expansivities and compressibilities are similar: α _a  = 8.2(3) and α _c  = 10.68(9) (10^?6 K^?1); β _a  = 11.4(3) and β _c  = 15.9(3) (10^?4 GPa). Hydration increases both the bulk thermal expansivity and compressibility, but decreases the anisotropy of structural expansion and compression. Complementary Raman and Fourier transform infrared (FTIR) spectroscopy shows multiple structural hydration sites. Low-temperature and high-pressure FTIR spectroscopy (15–300 K and 0–28 GPa) confirms that the multiple sites are structurally unique, with zero-pressure intrinsic anharmonic mode parameters between ?1.02 × 10^?5 and +1.7 × 10^?5 K^?1, indicating both weak hydrogen bonds (O–H···O) and strong OH bonding due to long O···O distances.     

The influence of thermal and cyclic stressing on the strength of rocks from Mount St. Helens, Washington

Stratovolcanoes and lava domes are particularly susceptible to sector collapse resulting from wholesale rock failure as a consequence of decreasing rock strength. Here, we provide insights into the influence of thermal and cyclic stressing on the strength and mechanical properties of volcanic rocks. Specifically, this laboratory study examines the properties of samples from Mount St. Helens; chosen because its strength and stability have played a key role in its history, influencing the character of the infamous 1980 eruption. We find that thermal stressing exerts different effects on the strengths of different volcanic units; increasing the heterogeneity of rocks in situ. Increasing the uniaxial compressive stress generates cracking, the timing and magnitude of which was monitored via acoustic emission (AE) output during our experiments. AEs accelerated in the approach to failure, sometimes following the pattern predicted by the failure forecast method (Kilburn 2003). Crack damage during the experiments was tracked using the evolving static Young’s modulus and Poisson’s ratio, which represent the quasi-static deformation in volcanic edifices more accurately than dynamic elastic moduli which are usually implemented in volcanic models. Cyclic loading of these rocks resulted in a lower failure strength, confirming that volcanic rocks may be weakened by repeated inflation and deflation of the volcanic edifice. Additionally, volcanic rocks in this study undergo significant elastic hysteresis; in some instances, a material may fail at a stress lower than the peak stress which has previously been endured. Thus, a volcanic dome repeatedly inflated and deflated may progressively weaken, possibly inducing failure without necessarily exceeding earlier conditions.     

Complex environmental gradients predict distributions of river-dependent plants in eastern Australia

We used principal components analysis and multiple logistic regression to investigate the relationships between environmental variables and the distributions of 71 species of river-dependent vascular plants in north-eastern New South Wales, Australia. Our analysis defined seven main environmental factors, summarised (in order of decreasing frequency of statistically significant association with species distributions) as exposure, salinity, stream size, stone scarcity, nutrient enrichment, grazing pressure and rockiness. The main environmental correlates of the presence or absence of macrophyte species in our study were broadly similar to those reported elsewhere, but the relatively low apparent importance of nutrients and grazing was unexpected. We were not able to fully separate the effects of climate-related and non-climatic environmental variables because variables of both types loaded strongly on some principal components, but we suggest that both types of variables should be included in models that aim to forecast potential shifts in plant distributions under projected climatic change. Vascular plants have been neglected in monitoring programs for Australian rivers and their conservation requires a better understanding of patterns and trends in distribution and abundance.