Abstract Basaltic fissure eruptions may evolve rapidly and unpredictably complicating hazard management. Localization of an elongate fissure to one or more focused vents may take days to months, and depends on fluid dynamic processes, such as thermally-driven viscous fingering, in the sub-volcanic plumbing system. However, fluid dynamics in a dyke geometry are poorly understood. We perform scaled analogue experiments to investigate convective magma exchange flow within a dyke-like conduit, and discover flow regimes ranging from chaotic mingling to stable, well-organized exchange, over the parameter space relevant for natural eruptions. Experiments are scaled via the Grashof number Gr, which is a Reynolds number for buoyancy-driven exchange flows. We propose that chaotic exchange at high Gr hinders thermally-driven localization by suppressing viscous fingering, whereas flow organization at low Gr enhances localization. Consequently, progressive decrease in Gr through increasing magma viscosity or decreasing dyke width pushes a fissure eruption towards a tipping point that results in rapid localization. Our findings indicate that current conceptual models for magma flow in a dyke require revision to account for this convective tipping point, and provide a quantitative framework for understanding the evolution of fissure eruptions.

中文翻译：

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对流临界点启动玄武岩裂隙喷发的定位

摘要 玄武岩裂隙喷发可能发展迅速且不可预测，使灾害管理复杂化。将细长裂缝定位到一个或多个集中喷口可能需要数天到数月的时间，并且取决于火山下管道系统中的流体动力学过程，例如热驱动的粘性指法。然而，人们对堤坝几何中的流体动力学知之甚少。我们进行了比例模拟实验，以研究堤坝状管道内的对流岩浆交换流，并在与自然喷发相关的参数空间中发现从混沌混合到稳定、组织良好的交换的流态。实验通过 Grashof 数 Gr 进行缩放，Gr 是浮力驱动的交换流的雷诺数。我们提出高 Gr 下的混沌交换通过抑制粘性指法来阻碍热驱动的定位，而低 Gr 下的流动组织增强了定位。因此，通过增加岩浆粘度或减小岩脉宽度，Gr 的逐渐减少将裂缝喷发推向导致快速定位的临界点。我们的研究结果表明，目前岩脉岩浆流动的概念模型需要修订以解释这一对流临界点，并为理解裂隙喷发的演变提供定量框架。