Rainfall-related debris flows in Carhuacocha Valley, Cordillera Huayhuash, Peru

Continuous heavy rainfall hit northern Peru in the second half of the 2008/2009 summer season. From the end of January to the beginning of March, the Cordillera Huayhuash experienced abnormally high precipitations that exceeded 270?mm. The antecedent rainfall, aggravated with a severe rainstorm of 20?mm on March 7 triggered a large debris flow in the upper Carhuacocha Valley early in the morning on March 8. The debris flow interrupted drainage from the upper part of the valley damming a lake in the narrow depression between the trough slope and the lateral moraine. As a result of the drainage interruption, water percolated through the moraine dam of Cangrajanca Lake where a secondary mass movement occurred in its inner slope. In September 2009, we mapped the debris flow and related landforms and estimated the total area and volume of both mass movements using geodetic measurements. About 104,000?m³ of sediments was moved from the trough slope towards the moraine from which 534,000?m³ flowed to Cangrajanca Lake subsequently. We analysed the rainfall conditions that triggered the debris flow using rainfall data from the nearby stations. We also compared the precipitation preceding the event with the rainfall thresholds for debris flow initiation.     

Choosing Between Two Kind of Sampling Patterns Using Geostatistical Simulation: Regularly Spaced or at High Uncertainty Locations?

Data from a mineral deposit are commonly obtained by core drilling. This kind of sampling involves high costs, limiting the number of drill holes. Additional holes should be located to bring the maximum benefit. The benefit can be evaluated by various ways and must take into account the goals of sampling. This article presents a case study where the deposit has been sampled and the new drillings must be added to reduce the uncertainty about a transfer function, Net Present Value (NPV) of the mining project. There are basically two ways to choose locations where new drillings should be placed for cases where the aim of sampling is to reduce uncertainty about a global function: the addition of new drillings outlining a quasi regular grid with previously collected drillings or the addition of new drillings on the locations of high uncertainty about the attribute of interest (or the attribute that is considered most influential in the transfer function). The performances of these patterns on reducing the uncertainty measured by the function selected are compared. The results point out that the most efficient pattern relates to the distribution (histogram) of the uncertainty about the attribute of interest. Thus, the choice of which sampling pattern should be adopted varies depending on data distribution and its influence on the transfer function.     

Hägerstrand meets big data: time-geography in the age of mobility analytics

Journal of Geographical Systems -     

Evaluating the genetic effects of the invasive Ocenebra inornata on the native oyster drill Ocenebra erinacea

Studies focusing on the effect of invasive species on the genetic diversity of native marine invertebrates remain scant. Here we report diversity among French populations of the intertidal gastropod Ocenebra erinacea (Linnaeus, 1758) sampled in the presence and absence of the invasive Ocenebra inornata (Recluz, 1851). Between 1999 and 2004, a total of 352 individuals of O. erinacea was collected from 15 sites (five of which had the invasive present) and was genotyped at the mitochondrial locus Cytochrome Oxidase 1 (cox1). No statistical difference was observed between polymorphism levels recorded within native populations exposed to the invasive, compared with populations sampled in the absence of O. inornata. No sign of native population decline was detected in response to the invader. While significant shifts in native O. erinacea population sizes have previously been reported in the literature, genetic effects may take longer to accumulate, or may be undetectable without a larger panel of genetic markers. By contrast, large genetic distances and significant population differentiation were recorded between Atlantic and Mediterranean O. erinacea samples, suggesting that these populations have distinct evolutionary histories. Comparison of genetic divergence within the closely related genus Nucella suggests that the Atlantic populations of O. erinacea and those from Thau Lagoon in the Mediterranean may belong to different species or subspecies.     

Phytoliths in palaeoecology

With increasing interest in climate change and other issues associated with the history of the environment and anthropogenic evolution there is an ongoing requirement to investigate the Earth's natural systems. A key approach is for scientists to look back into geological time, perhaps millions of years, to see how the world has reacted to natural climatic changes in the past. Using evidence from the fossil record, fluctuations in palaeoclimate can be assessed with reference to changes in global floral and faunal patterns. Phytoliths, Greek for 'plant stones', is a fossil group that is being increasingly utilized in the understanding of past climates and environments.     

Contemporary Eolian Sediments in the Alpine Zone,Colorado Front Range

Particle-size distribution, mineralogy, sphericity, and weathering characteristics from eolian material deposited on four snow patches in the alpine zone of the Colorado Front Range are reviewed against information available on the role of eolian transport. A comparison is also made with particle-size distributions from various tundra surfaces and other soil-loss processes. The eolian deposits exhibit properties intermediate between those of loesses and cover sands. Eolian transport exhibits a sharp drop in competence from alpine ridge crest to valley bottom.     

WEATHERING TRENDS IN FINE DEBRIS BENEATH A SNOW PATCH,NIWOT RIDGE,FRONT RANGE,COLORADO

Seven soil pits dug in a downhill sequence beneath Martinelli snow patch, Niwot Ridge, Front Range, Colorado, reveal that soils are coarse-grained with only limited evidence of silt translocation. Clay mineralogy within the pits exhibits a widespread and distinct change at a depth of ～15–20 cm. The most common characteristic of this change is a distinct increase in vermiculite in the lower layer, usually accompanied by a decrease in kaolinite and/or smectite. This pattern is interpreted to reflect decreased weathering intensity with depth. Microenvironments beneath the snow patch which exhibit high chemical weathering rates on coarse surficial debris also appear to experience high rates of clay production relative to referenced dry alpine sites, with specific clay mineralogies varying in a fashion commonly found in humid temperate environments. Data generated in this study appear to provide site-specific support for the regionally-developed Synthetic Alpine Slope Model. Spatial variations in eolian additions and meltwater produce complex patterns in chemical weathering of fines beneath large snow patches, although the nature of clay-mineral change is typical of humid, temperate, mid-latitude environments. [Key words: chemical weathering, alpine environments, clay mineralogy, Synthetic Alpine Slope Model.]     

From aqueous solution to solid solutions: A process oriented review of the work performed within the FUNMIG project

The Fundamentals of Radionuclide Migration (FUNMIG) project was organised in some Research and Technological Development Components (RTDCs) integrated by a number of Work Packages (WP’s) attempting to cover the key migration processes at different scales (laboratory to repository) and in different geological media, mainly clay and granite, but also some salt rock related work was performed. The main RTDCs of interest for this review paper are numbers 1 and 2, which concerned laboratory studies of well-established and less-established migration processes. Some additional interesting outcomes arise also from RTDCs 3, 4 and 5 devoted to the upscaling and applicability of migration processes to clay, granite and salt rock environments, respectively. This review discusses the contribution of the various parts of the FUNMIG project in the process oriented context of understanding the mechanistic approximation to what can be seen as the final and thermodynamically stable stage of the long chain of processes which are covered under the general term of sorption and that culminate in the formation of solid solutions.     

Satellite-derived estimates of potential carbon sequestration through afforestation of agricultural lands in the United States

Afforestation of marginal agricultural lands represents a promising option for carbon sequestration in terrestrial ecosystems. An ecosystem carbon model was used to generate new national maps of annual net primary production (NPP), one each for continuous land covers of ‘forest’, ‘crop’, and ‘rangeland’ over the entire U. S. continental area. Direct inputs of satellite “greenness” data from the Advanced Very High Resolution Radiometer (AVHRR) sensor into the NASA-CASA carbon model at 8-km spatial resolution were used to estimate spatial variability in monthly NPP and potential biomass accumulation rates in a uniquely detailed manner. The model predictions of regrowth forest production lead to a conservative national projection of 0.3 Pg C as potential carbon stored each year on relatively low-production crop or rangeland areas. On a regional level, the top five states for total crop afforestation potential were: Texas, Minnesota, Iowa, Illinois, and Missouri, whereas the top five states for total rangeland afforestation potential are: Texas, California, Montana, New Mexico, and Colorado. Afforestation at this level of intensity has the capacity to offset at least one-fifth of annual fossil fuel emission of carbon in the United States. These projected afforestation carbon gains also match or exceed recent estimates of the annual sink for atmospheric CO₂ in currently forested area of the country.     

Enigmatic Efflorescence in Kärkevagge, Swedish Lapland: The Key to Chemical Weathering?

The second marvel to catch the eye of the visitor to Kärkevagge, after the impressive boulder deposit on the floor of the valley, is the series of prominent white stripes running down the valley's dark cliffs. Streams and springs descending the eastern flank of Kärkevagge are marked by the presence of whitish coatings on the black rock surfaces and on cobbles lining ephemeral waterways. These were referred to as 'lime crusts' by early investigators, but they are not reactive to HCl. We believe that they are a precipitate resulting from acid attack on the local rocks. Pyrite is common in many of the rocks in the valley and its oxidation produces sulfuric acid. As the dissolved mineral elements are carried in the drainage water, efflorescence forms on the surfaces where the water flows due to evaporation or to changes in temperature. The exact mineralogy of the white crusts is unknown, but the crusts are dominated by Al, S, and O, and in some cases by Ca, depending on the substrate and local conditions. Gypsum, illite, and chlorite have been identified by X–ray diffraction of some scrapings of white–coated rocks. However, we believe that some unidentified oxy–hydroxy aluminum sulfates make up the bulk of the precipitates.