Schaefer, C.J. and Kattenhorn, S.A. (2003)
Thermal modeling of the cooling history of a basalt lava flow: Effect of flow shape and thermal perturbations induced by inflation fissures
Eos, Transactions of the American Geophysical Union, 84.
We use the finite element code ABAQUS to model the thermal evolution of small aspect ratio flows, both with and without an inflation fissure. The program accounts for radiation of heat and convection at exposed boundaries, latent heat of crystallization, and conduction of heat into the underlying substrate. In models that do not include an inflation fissure, the results predict that the final portion of a lava flow to solidify occurs slightly below the center of the flow, in agreement with field observations and previous analytical and numerical model results. Using the assumption that cooling fractures grow approximately perpendicular to isotherms, predicted isotherm patterns can be reconciled with fracture characteristics in cooled ESRP flows. The incremental introduction of an inflation fissure during cooling results in a one-month shorter time to complete solidification and significantly perturbs the isotherm patterns, and hence cooling fracture characteristics, of the flow. Furthermore, the inflation fissure dictates the location of the final portion of the flow to solidify (the "lava core") and may even cause the flow interior to segment into multiple lava cores. Based on these model results and our field observations of inflation fissure geometries, we hypothesize that the lava cores ultimately undergo rapid convective cooling and intense fracturing in response to being pierced by an inflation fissure, resulting in the development of a highly fractured zone (or "entablature") slightly below the flow center.
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