Revolving rivers in sandpiles: from continuous to intermittent flows

In a previous paper [Phys. Rev. Lett. 91, 014501 (2003)], the mechanism of "revolving rivers" for sandpile formation is reported: as a steady stream of dry sand is poured onto a horizontal surface, a pile forms which has a river of sand on one side owing from the apex of the pile to the edge of the base. For small piles the river is steady, or continuous. For larger piles, it becomes intermittent. In this paper we establish experimentally the "dynamical phase diagram" of the continuous and intermittent regimes, and give further details of the piles topography, improving the previous kinematic model to describe it and shedding further light on the mechanisms of river formation. Based on experiments in Hele-Shaw cells, we also propose that a simple dimensionality reduction argument can explain the transition between the continuous and intermittent dynamics.Comment: 8 pages, 11 figures, submitted to Phys Rev

Evolution and the Second Law of Thermodynamics: Effectively Communicating to Non-Technicians

Given the degree of disbelief in the theory of evolution by the wider public, scientists need to develop a collection of clear explanations and metaphors that demonstrate the working of the theory and the flaws in antievolutionist arguments. This paper presents tools of this sort for countering the anti-evolutionist claim that evolutionary mechanisms are inconsistent with the second law of thermodynamics. Images are provided to replace the traditional misunderstanding of the law, i.e., “everything always gets more disordered over time,” with a more clear sense of the way in which entropy tends to increase allowing a thermally isolated system access to a greater number of microstates. Accessible explanations are also provided for the ways in which individual organisms are able to minimize entropy and the advantages this conveys

Evaluating hydrology preservation of simplified terrain representations

We present an error metric based on the potential energy of water flow to evaluate the quality of lossy terrain simplification algorithms. Typically, terrain compression algorithms seek to minimize RMS (root mean square) and maximum error. These metrics fail to capture whether a reconstructed terrain preserves the drainage network. A quantitative measurement of how accurately a drainage network captures the hydrology is important for determining the effectiveness of a terrain simplification technique. Having a measurement for testing and comparing different models has the potential to be widely used in numerous applications (flood prevention, erosion measurement, pollutant propagation, etc). In this paper, we transfer the drainage network computed on reconstructed geometry onto the original uncompressed terrain and use our error metric to measure the level of error created by the simplification. We also present a novel terrain simplification algorithm based on the compression of hydrology features. This method and other terrain compression schemes are then compared using our new metric

The Carboniferous Southern Pennine Basin, UK

Many of the Carboniferous outcrops located in the Derbyshire region of the Peak District National Park, UK, have provided sites for both significant and pioneering research relating to the clastic sedimentology of marine palaeoenvironments, particularly so during the 1960s and 1970s when early models describing the sedimentary architecture of fluvio-deltaic, submarine slope and deep-marine submarine-fan sedimentation were first developed. The area was subject to hydrocarbon exploration from the 1920s to 1950s, which although unsuccessful in economic terms left a legacy of sub-surface data. Despite a long-history of sedimentological research, the deposits exposed at several classic localities in the Pennine Basin continue to broaden and challenge our current understanding of sedimentary processes to this day

Model a Catchment Basin

The purpose of this resource is to introduce what a catchment basin is and how it works. Students will make a 3-dimensional model of a catchment basin to understand how water moves through the basin and explore how water is affected when there are changes in the basin. Educational levels: Primary elementary, Intermediate elementary, Middle school, High school

Glacial Geology of the Androscoggin River Valley in Oxford County, Western Maine

Guidebook for field trips in southern and west-central Maine, October 13, 14 and 15, 1989: New England Intercollegiate Geological Conference 81st annual meeting: Trip B-2; C-

Isotopic characteristics of the Garonne River and its tributaries

The Garonne is the largest river in the south-west of France, and its drainage basin stretches between the Pyrenees and the Massif Central mountains. Until now, no water stable isotope study has been performed on the whole Garonne river basin which is composed of different geological substrata, and where the water resources are limited during the dry summer period. This study focuses on the Garonne river and its tributaries from the Pyre´ne´es foothill upstream to its confluence with the Lot River downstream. The aim of the study is to determine the origins of the surface waters using their chemical and stable isotopic compositions (18O, D and 13C), to better understand their circulation within the drainage basin and to assess the anthropogenic influences. The Garonne displays a specific 18O seasonal effect, and keeps its Pyre´nean characteristics until its confluence with the Tarn River. The difference in the dissolved inorganic carbon (DIC) comes mainly from the change in lithology between the Pyre´ne´es and the Massif Central mountains. Agriculture activity is only detected in the small tributaries