Explosive Volcanism: Controls on the Style and Intensity of Historical Eruptions of Vesuvius

霍顿-EAR-0087586维苏威火山可能是世界十年来最危险的火山。60万人居住在火山口周围10公里的范围内，历史上它经历了9次大喷发(VEI 3)和多次小型喷发。这座重要的火山是许多小组早期广泛的实地和岩石学研究的主题，这些研究为这一计划提供了一个支撑框架。维苏威火山历史上的特征是持续的爆炸性喷发，这是一种极具破坏性的事件，稳定喷发的羽流可能会逐渐或突然地让位于柱体坍塌和/或熔融岩浆作用。这项研究的重点是在公元79年期间，从稳定的普林尼安喷发到产生极具破坏性的火山碎屑密度流的云雾状爆炸的突然转变的原因。公元79年的喷发，摧毁了庞贝和赫库兰尼姆(Lirer等人，1973年，Sigurdsson等人。1982、1985，Cioni et al.(1992)，通常被认为是普林尼安火山作用的典型例子。该程序将描述喷发强度和类型变化的宏观参数与浮石结构和化学的微观观察联系起来。这项研究将(I)描述从单个喷口喷发出来的火山岩碎片(火山碎屑)的混合物，以及(Ii)对比气泡形成和微晶结晶的模式，以反映岩浆成分、喷发方式和喷发强度的广泛光谱。火山碎屑中的大小晶体(斑晶和微石)和气泡(气泡)在洞室和管道中冻结在母批岩浆的历史方面，代表着了解火山地下演化的“微观窗口”。我们将解释喷发风格关键变化前后泡沫度和微晶结晶度的平均值和极值的变化。通过使用这种严格限制的历史喷发，我们预计这项工作的结果将广泛应用于记录较少的历史性或史前喷发，并将极大地提高我们对火山喷发期间喷发方式/强度突然变化的理解，并有助于预测维苏威火山(和其他锥形火山)下一次喷发的时间，而是它将如何喷发，从灾害管理和减灾的角度来看，这是一个同样重要的问题。

HoughtonEAR-0087586Vesuvius is perhaps the most dangerous of the world's Decade Volcanoes. 600 000 people live within 10 km of the crater and it has experienced 9 large (VEI 3) and numerous minor eruptions in historical times. This important volcano has been the subject of extensive earlier field and petrological studies by many groups, which supply an underpinning framework for this program. The sustained explosive eruptions, which characterize Vesuvius's history, are highly destructive events in which stable eruption plumes may give way gradually or abruptly to column collapse and/or phreatomagmatism. The study focuses on the cause of the abrupt transition from stable Plinian eruption to phreatomagmatic explosions generating highly destructive pyroclastic density currents during the 79 AD eruption. The AD 79 eruption, which destroyed Pompeii and Herculaneum (Lirer et al 1973, Sigurdsson et al. 1982, 1985, Cioni et al. 1992), is generally regarded as the 'type' example of Plinian volcanism. The program links macroscopic parameters describing the changes in eruption intensity and style with microscopic observations of pumice texture and chemistry. The study will (i) characterize the mixture of volcanic rock fragments (pyroclasts) emerging from single eruptive vents at a single moment and (ii) contrast patterns of vesiculation and microlite-crystallization for wide spectra of magma composition, and eruptive style and intensity. Large and small crystals (phenocrysts and microlites respectively) and gas bubbles (vesicles) in pyroclasts 'freeze in' aspects of the history of the parent batch of magma in the chamber and conduit, and represent 'microscopic windows' into the subsurface evolution of the volcano. We will interpret the changes in mean and extreme values of vesicularity and microlite-crystallinity before and after the key change in eruptive style. By using such well-constrained historical eruptions, we expect that the results of this work will have broad application to less well-documented historic or prehistoric eruptions and will greatly improve our understanding of abrupt changes in eruptive style/intensity during explosive volcanism, and aid in forecasting not when Vesuvius (and other cone volcanoes) will next erupt but how it will erupt, a question that is equally important from a perspective of hazard management and mitigation.