Rheological Evolution of Basaltic Lava Flows During Cooling and Crystallization

玄武岩覆盖了地球和其他几个行星和卫星表面的大部分。熔岩流和其他结构（如圆锥体和圆顶）的形态与熔岩的物理性质、渗出率和环境因素（如表面介质（海底与陆上）和坡度）有关。熔岩的重要物理性质包括粘度、屈服强度、热扩散率和热容，所有这些都随温度（T）和晶体分数（#966;，其本身随T变化）而变化。熔体粘度可以在一个单一的喷发事件中变化许多数量级，尽管最近的进展结晶玄武岩浆的流变学仍然相对较差的约束。PI和研究生将在适合玄武岩火山作用的条件下测量来自各种构造环境的玄武岩熔岩的流变学和热特性，并将这些特性的变化作为T，成分（X）和#966;的函数。其目的是提供一个更好的理解，这些属性如何在一个特定的时刻，在整个流动，并在一个单一的量子岩浆从喷口到最终的侵位。通过结合岩浆的流变学和热性质的信息，我们试图探索潜在的复杂的反馈之间的关系，结晶，潜热释放，熔体粘度和屈服强度，控制整体流变学和流动形态。待研究的熔岩样本将来自基拉韦厄（夏威夷）、拉基（冰岛）、埃特纳（意大利）、富埃戈和帕卡亚（危地马拉）以及阿纳尔（哥斯达黎加）。实验测量将包括：使用平行板和同心圆筒粘度计，测定熔体粘度从1到1012 Pa.s作为温度的函数。屈服强度将在与熔岩流相关的低应力下通过测量应变率作为应力的函数来确定，用于精心选择的时间序列实验，以获得具有不同晶体含量的样品。液体热容和熔化焓将通过滴量热法测定。玻璃和过冷液体的热容，以及过冷条件下的结晶焓，将通过差示扫描量热法测定。熔体粘度和多相岩浆流变学（有效粘度和表观屈服强度）将被参数化为T，X和#966;的函数。该研究计划将被划分为较小的项目，这将为综合研究生和本科生的培训和教育提供许多机会。该项目将提供数据和模型，并将其应用扩展到自然灾害、行星地质学和材料科学。

Basaltic lavas cover large portions of the surface of the Earth and several other planets and moons. The morphology of lava flows and other structures such as cones and domes is related to the physical properties of the lava, the effusion rate, and environmental factors such as surface medium (submarine vs subaerial) and slope. Important physical properties of lavas include viscosity, yield strength, thermal diffusivity and heat capacity, all of which vary with temperature (T) and crystal fraction (φ, which itself varies with T). Melt viscosity can vary by many orders of magnitude within a single eruptive event, and despite recent advances the rheology of crystallizing basaltic magma is still relatively poorly constrained. The PI and graduate students will measure the rheological and thermal properties of basaltic lavas from various tectonic settings at conditions appropriate to basaltic volcanism, and model variations in these properties as a function of T, composition (X) and φ. The aim is to provide a better understanding of how these properties can vary across a flow at a particular instant in time, and within a single quantum of magma from vent to final emplacement. By combining information on rheological and thermal properties of magma, we seek to explore potentially complex feedback relationships between crystallization, latent heat release, melt viscosity and yield strength that control the overall rheology and flow morphology. The lava samples to be studied will come from Kilauea (Hawaii), Laki (Iceland), Etna (Italy), Fuego and Pacaya (Guatemala), and Arenal (Costa Rica). Experimental measurements will include: determination of melt viscosity from 1 to 1012 Pa.s as a function of temperature, using parallel-plate and concentric-cylinder viscometers. Yield strength will be determined at low stresses relevant to lava flows by measuring strain rate as a function of stress, for carefully selected time series experiments to obtain samples with different crystal contents. Liquid heat capacity and the enthalpy of fusion will be determined by drop calorimetry. Heat capacity of glasses and supercooled liquids, and enthalpy of crystallization under supercooled conditions, will be determined by differential scanning calorimetry. Melt viscosity and multiphase magma rheology (effective viscosity and apparent yield strength) will be parameterized as a function of T, X and φ. The research program will be divided into smaller projects that will provide many opportunities for integrated graduate and undergraduate training and education. The project will provide data and models with applications extending to natural hazards, planetary geology and materials science.