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The Influence of Slope Breaks on Lava Flow Surface DisruptionChanges in the underlying slope of a lava flow impart a significant fraction of rotational energy beyond the slope break. The eddies, circulation and vortices caused by this rotational energy can disrupt the flow surface, having a significant impact on heat loss and thus the distance the flow can travel. A basic mechanics model is used to compute the rotational energy caused by a slope change. The gain in rotational energy is deposited into an eddy of radius R whose energy is dissipated as it travels downstream. A model of eddy friction with the ambient lava is used to compute the time-rate of energy dissipation. The key parameter of the dissipation rate is shown to be rho R(sup 2/)mu, where ρ is the lava density and mu is the viscosity, which can vary by orders of magnitude for different flows. The potential spatial disruption of the lava flow surface is investigated by introducing steady-state models for the main flow beyond the steepening slope break. One model applies to slow-moving flows with both gravity and pressure as the driving forces. The other model applies to fast-moving, low-viscosity, turbulent flows. These models provide the flow velocity that establishes the downstream transport distance of disrupting eddies before they dissipate. The potential influence of slope breaks is discussed in connection with field studies of lava flows from the 1801 Hualalai and 1823 Keaiwa Kilauea, Hawaii, and 2004 Etna eruptions.
Document ID
20140010487
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Glaze, Lori S.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Baloga, Stephen M.
(Proxemy Research, Inc. Gaithersburg, MD, United States)
Fagents, Sarah A.
(Hawaii Univ. Honolulu, HI, United States)
Wright, Robert
(Hawaii Univ. Honolulu, HI, United States)
Date Acquired
August 6, 2014
Publication Date
January 1, 2014
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
GSFC-E-DAA-TN13655
Funding Number(s)
CONTRACT_GRANT: NNXAR10G
CONTRACT_GRANT: NNX10AP63G
WBS: WBS 811073.02.01.05.80
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
disruption
lava
surface
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