A simple and efficient GIS tool for volume calculations of submarine landslides

A numeric tool is presented for calculating volumes of topographic voids such as slump scars of landslides, canyons or craters (negative/concave morphology), or alternatively, bumps and hills (positive/convex morphology) by means of digital elevation models embedded within a geographical information system (GIS). In this study, it has been used to calculate landslide volumes. The basic idea is that a (singular) event (landslide, meteorite impact, volcanic eruption) has disturbed an intact surface such that it is still possible to distinguish between the former (undisturbed) landscape and the disturbance (crater, slide scar, debris avalanche). In such cases, it is possible to reconstruct the paleo-surface and to calculate the volume difference between both surfaces, thereby approximating the volume gain or loss caused by the event. I tested the approach using synthetically generated land surfaces that were created on the basis of Shuttle Radar Topography Mission data. Also, I show the application to two real cases, (1) the calculation of the volume of the Masaya Slide, a submarine landslide on the Pacific continental slope of Nicaragua, and (2) the calculation of the void of a segment of the Fish River Canyon, Namibia. The tool is provided as a script file for the free GIS GRASS. It performs with little effort, and offers a range of interpolation parameters. Testing with different sets of interpolation parameters results in a small range of uncertainty. This tool should prove useful in surface studies not exclusively on earth

Habitat mapping on a deep-water coral reef off Norway, with a comparison of visual and computer-assisted sonar imagery interpretation

The Sula Ridge Reef complex, a large cold-water coral reef structure on the mid-Norwegian shelf built mainly by Lophelia pertusa, was mapped entirely using a high-resolution sidescan sonar. In addition, a dense echosounding grid, underwater vide observations and dives using the manned research submersible Jago, provided precise high-quality ground-truthing, and allowed a detailed interpretation of the reef structure and its surrounding geological features. The result of this visual sidescan sonar interpretation is a facies map that delineates different potential habitats within the coral reef environment, e.g. live coral reef, dead coral structure and sediment-covered coral/rubble, etc. In an attempt to improve this interpretation, computer-assisted image analysis was applied to a representative section of the sonar data to try to reveal patterns 'invisible' to the human eye (using the TexAn software). Texture analysis uses Grey-Level Cooccurrence Matrices (GLCMs) to calculate statistical indices quantifying the distribution of grey levels and their spatial relationship within the image. For example, regions of rough textures (coral mounds) can be distinguished from areas of smooth background sediment or zones of heterogeneous texture resulting from sediment-covered coral debris and dropstones colonized by sponges. The results of the computer-assisted approach were carefully compared with the earlier visual interpretation ro identify the differences and to see where the interpretation could be improved. Overall, it shows that texture analysis is a useful tool to make facies/habitat mapping from sidescan sonar easier and faster, revealing details overlooked during visual interpretation. However, validation of certain details by an experienced interpreter is still necessary, and therefore visual and computer-assisted interpretation should be used as complementary tools

Climate change and the Viking-age fjord environment of the Eastern Settlement, South Greenland

An electron-proton/ion collider facility (eRHIC) is under consideration at Brookhaven National Laboratory (BNL). Such a new facility will require the design and construction of a new optimized detector profiting from the experience gained from the H1 and ZEUS detectors operated at the HERA collider at DESY. The details of the design will be closely coupled to the design of the interaction region, and thus to the machine development work in general. An overview of the accelerator and detector design concepts will be provided.Comment: 5 pages, 3 figures, Invited talk at the International Europhysics Conference on High-Energy Physics, Lisbon, Portugal, July 21-27, 200