It is increasingly recognized that the gravitational stability of explosive eruption columns is governed by complex ash-pumice-gas (multiphase) interactions as well as the mechanics of turbulent entrainment in the lower momentum-driven (fountain) and upper buoyancy-driven (plume) regions of typical Plinian eruption columns (volcanic jets). We use analog experiments on relatively dense mono- and bi-disperse particle-freshwater and particle-saltwater jets injected into a linearly stratified saltwater layer to revisit, characterize and understand how transitions among Buoyant Plume (BP), Total Collapse (TC) and Partial Collapse (PC) multiphase jet regimes in a traditional source strength (−Ri₀) - particle concentration (ϕ₀) parameter space are modified by particle inertial effects expressed through a Stokes number (St) and particle buoyancy effects expressed through a Sedimentation number (Σ). We show that “coarse particles” (1.4 ≤St ≤ 6.0) enhance entrainment and modify significantly published conditions favoring BP and TC jets. Furthermore, the transition between BP and TC regimes occurs smoothly over a PC regime that extends a large \(-\text {R}\text {i}_{0} \leftrightarrow \phi _{0}\) parameter space. Large volume annular sedimentation waves excited periodically at the fountain-plume transition height and the cloud level of neutral buoyancy (LNB) in PC and TC regimes lead to “phoenix clouds” spreading at multiple altitudes and build terraced deposits. Applied to volcanic jets, we develop a new set of conceptual models for jets in the BP, TC and PC regimes that make explicit links among source parameters, column heights, sedimentation wave properties, cloud structures and deposit architectures. These conceptual models make predictions for cloud structures and deposit characteristics that agree with observations made for well-studied historic and pre-historic eruptions and explain the origin of common but enigmatic features of proximal explosive eruption deposits, such as alternating air-fall and pyroclastic flow layering in subaerial deposits and terracing in submarine Catastrophic-Caldera Forming (CCF) eruption deposits. Additionally, our models provide guidance for real-time monitoring of eruption column stability for eruptions undergoing a typical BP→PC→TC regime evolution and predict pyroclastic flows to occur more frequently as columns transition from the PC→TC regime. Our experimental results combined with scaling considerations expressed through a set of new conceptual models provide exciting new pathways for future laboratory-, computer- and field-based studies of explosive eruptions.

人们越来越认识到，爆炸喷发柱的重力稳定性受复杂的灰-浮石-气体（多相）相互作用以及下部动量驱动（喷泉）和上部浮力驱动（羽流）的湍流夹带力学控制典型的普林尼亚喷发柱（火山喷流）的区域。我们对注入线性分层咸水层的相对密集的单分散和双分散颗粒淡水和颗粒咸水射流进行模拟实验，以重新审视、表征和了解浮力羽流 (BP)、完全坍塌 (TC) 和部分传统源强度 (−Ri ₀ ) - 粒子浓度 ( ϕ ₀ ) 下的坍缩 (PC) 多相射流状态) 参数空间由通过斯托克斯数 (St) 表示的粒子惯性效应和通过沉降数 (Σ) 表示的粒子浮力效应进行修改。我们表明“粗颗粒”（1.4 ≤St ≤ 6.0）增强了夹带并显着修改了有利于 BP 和 TC 射流的公开条件。此外，BP 和 TC 机制之间的过渡在扩展大\(-\text {R}\text {i}_{0} \leftrightarrow \phi _{0}\)参数空间。在 PC 和 TC 状态下，在喷泉-羽流过渡高度和中性浮力 (LNB) 云层周期性激发的大体积环形沉积波导致“凤凰云”在多个高度扩散并形成梯田沉积。应用于火山喷流，我们为 BP、TC 和 PC 状态的喷流开发了一套新的概念模型，这些模型在源参数、柱高、沉积波特性、云结构和沉积结构之间建立了明确的联系。这些概念模型对云结构和沉积物特征进行预测，这些预测与对经过充分研究的历史和史前喷发的观察结果一致，并解释了近端爆炸性喷发沉积物的常见但神秘特征的起源，例如地下沉积物中的交替空气坠落和火山碎屑流分层以及海底灾难性火山口形成 (CCF) 喷发沉积物中的梯田。此外，我们的模型为实时监测经历典型 BP→PC→TC 体系演化的喷发柱稳定性提供指导，并预测火山碎屑流在柱从 PC→TC 体系转变时更频繁地发生。我们的实验结果与通过一组新概念模型表达的缩放考虑相结合，为未来实验室、计算机和现场的爆炸性喷发研究提供了令人兴奋的新途径。我们的模型为实时监测喷发柱稳定性提供了指导，这些喷发经历了典型的 BP→PC→TC 体系演变，并预测火山碎屑流在柱从 PC→TC 体系转变时更频繁地发生。我们的实验结果与通过一组新概念模型表达的缩放考虑相结合，为未来实验室、计算机和现场的爆炸性喷发研究提供了令人兴奋的新途径。我们的模型为实时监测喷发柱稳定性提供了指导，这些喷发经历了典型的 BP→PC→TC 体系演变，并预测火山碎屑流在柱从 PC→TC 体系转变时更频繁地发生。我们的实验结果与通过一组新概念模型表达的缩放考虑相结合，为未来实验室、计算机和现场的爆炸性喷发研究提供了令人兴奋的新途径。