Thermal and Rheological Controls on the Emplacement of Basaltic Lava Flows

9902851现金玄武岩熔岩流虽然在各种条件下侵位，但根据流面形态和流动推进的机制，可以分为三种类型之一--Pahoe-hoe，`a`‘a，或块状。从定性上讲，不同流动类型的形成可以用熔岩结壳强度和流动内部流变性的差异来解释。然而，必须定量地了解不同流动类型之间转换的限制条件，以便准确地模拟流动机制，并预测喷发喷发期间熔岩流动的速度和最终范围。我们认为，这种理解的关键是量化控制熔岩壳稳定性的参数与随后熔岩流内部冷却(和结晶)之间的反馈。为此，我们将：(A)实地研究夏威夷(莫纳罗亚和基拉韦厄)和意大利(Mt.(B)实验室和理论研究，以确定晶体对熔岩流变学的影响，以及(C)非层流系统的模拟实验，以确定保存稳定结壳的极限流动条件。我们预计，这些结果将在模拟和预测熔岩流动行为方面有广泛的应用，此外还有助于悬浮流变学的研究和搅拌(破坏)流表面凝固的一般研究。

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.