Bulletin of the American Physical Society
77th Annual Meeting of the Southeastern Section of the APS
Volume 55, Number 10
Wednesday–Saturday, October 20–23, 2010; Baton Rouge, Louisiana
Session BA: The Role of Physics in Atmospheric, Ocean, and Earth Sciences |
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Chair: Solomon Bililign, North Carolina A&T University Room: Nicholson Hall 119 |
Thursday, October 21, 2010 8:30AM - 9:00AM |
BA.00001: The role of physics in atmospheric, ocean and Earth science Invited Speaker: The Earth system is a very complex system made of the Atmosphere, the Biosphere, the Hydrosphere, the Cryosphere and the solid portion of the Earth's surface. These components interact with each other in very complex highly nonlinear ways. Advances in remote sensing techniques and computational capabilities have allowed Earth system science to make substantial advances and contributions in the fields of geophysical fluid dynamics, chemistry, biology, cloud and aerosols dynamics and interactions, and computational science. Some of the major scientific achievements will be described. The scientific issues facing our field will be discussed, including challenges of climate and feedback mechanisms. Throughout the presentation, emphasis will be given to the physics behind our science. [Preview Abstract] |
Thursday, October 21, 2010 9:00AM - 9:30AM |
BA.00002: Mesoscale eddies and vertical mixing in the ocean Invited Speaker: Mesoscale eddies are fundamental players in the vertical transport and mixing in the ocean. Here we investigate the vertical velocities associated with coherent vortices using a high-resolution primitive-equation model in an idealized configuration and in a simulation of the Gulf of Mexico. In the vortex cores and inside intense vorticity filaments, the motion is strongly ageostrophic, and vertical velocities associated with vortices can reach unexpected magnitudes and levels of spatial complexity. Mesoscale anticyclones appear as ``islands'' of increased penetration of wind energy into the ocean interior. The wind energy injected at the surface is transferred at depth through the generation and subsequent straining effect of Vortex Rossby Waves (VRWs), and through near-inertial internal oscillations trapped inside anticyclonic eddies. [Preview Abstract] |
Thursday, October 21, 2010 9:30AM - 10:00AM |
BA.00003: Tracking the movement of magma through the crust in the East African rift Invited Speaker: Although fault and magmatic processes have achieved plate spreading at mid-ocean ridges throughout Earth's history, intense volcano-tectonic rifting episodes have rarely been observed. A 65 km-long segment of the subaerial Red Sea rift in Ethiopia experienced a major volcano-tectonic rifting episode in September 2005. Incipient seafloor spreading centers in the Afar rift are surrounded by continental crust and mantle lithosphere stretched and intruded during the past 30 Ma as Africa and Arabia have rifted apart above a mantle plume. We use seismic data and complementary space-based geodetic and remote sensing data to determine the length and timescales of magmatism and faulting, the partitioning of strain between faulting and magmatism, and their implications for the maintenance of along-axis segmentation. Most of the magma for the initial and subsequent 12 intrusions was sourced from the center of the Dabbahu-Manda Hararo rift segment. Strain is accommodated primarily by axial dike intrusions fed from mid-segment magma chamber(s). These findings show that episodic (approximate century interval), rapid opening of discrete rift segments is the primary mechanism of plate boundary deformation. The length scale ($\sim $65 km) and intensity of crustal deformation ($\sim $6 m), as well as the volume of intrusive and extrusive magmatism ($>$3 cubic km) provokes a re-evaluation of seismic and volcanic hazards in subaerial rift zones. [Preview Abstract] |
Thursday, October 21, 2010 10:00AM - 10:30AM |
BA.00004: Exploring the interior of an active volcano with deformation models Invited Speaker: The migration of restless magma within an active volcano produces a deformation signature at the Earth's surface. The internal structure of a volcano and specific movements of the magma control the actual deformation that we observe. Data from radar satellites can map this deformation for an entire volcanic system and ground-based seismic instruments can image the internal structure. Deformation models simulate this internal structure, subjected to the forces of magma movements, and provide the quantitative linkage between the observed surface deformation and the movements of magma at depth. Satellite radar data indicate that Okmok volcano, Alaska, subsided more than a meter during its eruption in 1997. The deformation pattern suggests magma extraction from a shallow reservoir. New seismic tomography reveals two weak zones within Okmok. The shallow weak zone corresponds to a region of fluid-saturated rock that extends from the caldera surface to a depth of 2 km. The deep weak zone indicates the presence of the magma chamber at a depth of about 4 km. We construct finite element models (FEMs) to simulate deformation caused by magma extraction from a chamber that is surrounded by a viscoelastic rind of country rock. Thermal models define the brittle-ductile transition and thickness of the viscoelastic rind. This assemblage, which represents the deep weak zone, is embedded in an elastic model domain that includes a shallow weak zone filling the caldera. Because the predicted surface deformation is the combined elastic and viscous response to magma extraction, these viscoelastic FEMs reduce the required magma chamber depressurization (compared to strictly elastic models) to within lithostatic constraints, while simultaneously predicting the magnitude and pattern of deformation observed with satellite radar data. More precisely, the satellite radar data are best predicted by an FEM simulating a rind viscosity of 7.5$\times $10$^{16}$ Pa$\cdot $s and a magma flux of -4.2$\times $10$^{9}$ kg/d from the magma chamber. Additionally, the shallow weak zone provides a co-eruption stress regime and neutral buoyancy horizon that support lateral magma propagation from the central magma reservoir to the observed lava extrusion near the rim of the caldera. [Preview Abstract] |
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