Thermal and Rheological Controls on the Emplacement of Basaltic Lava Flows

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9902851CashmanBasaltic lava flows, although emplaced under a wide range of conditions, can be classified as one of three types - pahoehoe, `a`a, or blocky - on the basis of both flow surface morphology and on the mechanism by which the flows advance. Qualitatively, the formation of distinct flow types can be explained by differences in strengths of lava crusts and in the rheologies of flow interiors. However, limiting conditions for transitions between flow types must be quantitatively understood for accurate modeling of the mechanics of flow, and for predicting the rates and ultimate extent of lava flow advance during effusive eruptions. We suggest that key to this understanding is quantification of feedback between parameters controlling the stability of lava crusts and the consequent cooling (and crystallization) of lava flow interiors. Toward this end, we will perform (a) field-based studies of lava flows in Hawai`i (Mauna Loa and Kilauea) and Italy (Mt. Etna) to document rates of lava cooling and crystallization, (b) laboratory and theoretical studies to determine the effect of crystals on lava rheology, and (c) analog experiments of non-laminar systems to determine limiting flow conditions for preservation of stable crusts. We anticipate that the results will have broad applications to modeling and predictions of lava flow behavior, in addition to contributing to research on suspension rheology and to general studies of surface solidification of stirred (disrupted) flows.