Sedimentary peels from pyroclastic density current deposits: revealing basal flow-boundary processes.

稀火山碎屑密度流（PDCs）代表了火山爆发期间发生的一些最移动的和最危险的事件。它们是低浓度气体和颗粒混合物的输运过程，属于颗粒密度流。它们可以直接从喷口喷出，也可以在距离喷发中心数公里的地方，通过密集的火山碎屑流的流剥离而产生。它们的低密度是它们高流动性的原因，使它们能够克服地形障碍，迄今为止，对它们的内部动力学知之甚少。在稀PDC中，颗粒既起驱动动量的作用，又构成合成存款。因此，对稀释PDC留下的交错层沉积物的沉积学研究是这些流动的最丰富和最具启发性的自然数据来源。一个独特的高分辨率的数据集，现在已经获得了通过浸渍的沉积物的通古拉瓦火山（厄瓜多尔）的2006年喷发与固化树脂在广泛的实地活动。这种技术允许生产沉积果皮，保留原始的颗粒组织和分层。由此产生的数据集是用于精细调查和教育目的的罕见工具。作为对沉积皮的补充，两次探地雷达和地面激光扫描测绘提供了关于矿床内部和表面三维几何形状的更多信息。我们计划通过实验室表征结合专门设计的，有针对性的模拟实验对这些数据集进行详细调查。我们的目标是获得独特的见解，在流动床界面的动态稀释PDCs和颗粒运输的形态动力学。Peel数据集还将作为学生、研究人员和公众教育传播工具的核心部分。

Dilute pyroclastic density currents (PDCs) represent some of the most mobile and dangerous events occurring during explosive volcanic eruptions. They are a transport process of gas and particle mixtures at low concentration that belong to the class of particulate density currents. They can be directly emitted from a vent or be produced kilometres away from the eruptive centre by flow stripping from dense pyroclastic flows. Their low density is responsible for their high mobility, allowing them to overcome topographic obstacles and to date, little is known of their internal dynamics.In a dilute PDC, particles play the role of both driving momentum and make up the resultant deposit. Sedimentological studies on the cross-bedded deposits left by dilute PDCs thus represent the richest and most revealing source of natural data for these flows. A unique high-resolution dataset has now been acquired by impregnating the deposits of the 2006 eruption of Tungurahua volcano (Ecuador) with a solidifying resin during extensive field campaigns. This technique permits to produce sedimentary peels that preserve both the original grain organization and stratification. The resulting data-set is a rare tool for fine-scale investigation and educational purposes. As a complement to the sedimentary peels, two surveys of ground penetrating radar and terrestrial laser scanner mapping provide additional information on the three dimensional geometry of the deposits, both internal and surficial. We plan a detailed investigation of these datasets through laboratory characterisation in combination with specially designed, targeted, analogue experiments. Our goal is to gain unique insights into the dynamics of dilute PDCs and the morphodynamics of grain transport at the flow-bed interface. The peel dataset will also serve as the central piece of an educational dissemination tool for students, researchers, and the public.