Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session B7: Emergent Patterns in Geophysical Processes |
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Sponsoring Units: DCMP Chair: Raymond Goldstein, University of Cambridge Room: Colorado Convention Center Korbel 4A-4B |
Monday, March 5, 2007 11:15AM - 11:51AM |
B7.00001: Dynamics of precipitation pattern formation at geothermal hot springs Invited Speaker: The spectacular terraced landscape at geothermal hot springs is a world-wide phenomenon, shown here to arise from the nonlinear interplay between turbulent fluid transport and precipitation dynamics. The system is modeled successfully using a discrete space-time model, justified both from renormalization group considerations and our experience modeling phase transition kinetics in condensed matter systems. A variety of scaling laws are predicted and compared with field observations. [Preview Abstract] |
Monday, March 5, 2007 11:51AM - 12:27PM |
B7.00002: Scaling in Columnar Joints Invited Speaker: Columnar jointing is a fracture pattern common in igneous rocks in which cracks self-organize into a roughly hexagonal arrangement, leaving behind an ordered colonnade. We report observations of columnar jointing in a laboratory analog system, desiccated corn starch slurries. Using measurements of moisture density, evaporation rates, and fracture advance rates, we suggest an advective-diffusive system is responsible for the rough scaling behavior of columnar joints. This theory explains the order of magnitude difference in scales between jointing in lavas and in starches. We investigated the scaling of average columnar cross-sectional areas in experiments where the evaporation rate was fixed using feedback methods. Our results suggest that the column area at a particular depth is related to both the current conditions, and hysteretically to the geometry of the pattern at previous depths. We argue that there exists a range of stable column scales allowed for any particular evaporation rate. [Preview Abstract] |
Monday, March 5, 2007 12:27PM - 1:03PM |
B7.00003: How the Icicle Got Its Shape Invited Speaker: The growth of icicles is considered as a free-boundary problem. A synthesis of atmospheric heat transfer, geometrical considerations, and thin-film fluid dynamics leads to a nonlinear ordinary differential equation for the shape of a uniformly advancing icicle, the solution to which defines a parameter-free shape which compares very favorably with that of natural icicles. Away from the tip, the solution has a power-law form identical to that recently found for the growth of stalactites by precipitation of calcium carbonate. This analysis thereby explains why stalactites and icicles are so similar in form despite the vastly different physics and chemistry of their formation. [Preview Abstract] |
Monday, March 5, 2007 1:03PM - 1:39PM |
B7.00004: Snow spikes: formation of laboratory penitentes Invited Speaker: Spike-shaped structures are produced by light-driven ablation in very different contexts. Penitentes 1–-4 m high are common on Andean glaciers, where their formation changes glacier dynamics and hydrology. Laser ablation can produce cones 10–-100 microns high with a variety of proposed applications in materials science. We report the first laboratory generation of centimeter-scale snow and ice penitentes. Systematically varying conditions allows identification of the parameters controlling the formation of ablation structures. We demonstrate that penitente initiation and coarsening require cold temperatures, so that ablation leads to sublimation. Once penitentes have formed, further growth of height can occur by melting. The penitentes initially appear as small structures (3 mm high) and grow by coarsening to 1-5 cm high. Our results are an important step towards understanding ablation morphologies. [Preview Abstract] |
Monday, March 5, 2007 1:39PM - 2:15PM |
B7.00005: Triboelectrification and Razorbacks: Geophysical Patterns Produced in Dry Grains Invited Speaker: |
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