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

维苏威火山可能是世界上最危险的十年火山。60万人居住在火山口10公里范围内，它经历了9次大喷发（VEI 3）和许多次小喷发。这个重要的火山已经成为许多小组广泛的早期野外和岩石学研究的主题，这些研究为本计划提供了基础框架。持续的爆炸性喷发是维苏威火山历史的特征，是高度破坏性的事件，在这种事件中，稳定的喷发羽流可能逐渐或突然让位给柱崩塌和/或呼吸岩浆作用。研究的重点是在公元79年火山喷发期间，从稳定的普林尼火山喷发突然转变为产生高度破坏性火山碎屑密度流的呼吸火山喷发的原因。公元79年的火山喷发摧毁了庞贝城和赫库兰尼姆（Lirer et al. 1973, Sigurdsson et al. 1982, 1985, Cioni et al. 1992），通常被认为是普林尼火山活动的“典型”例子。该程序将描述喷发强度和风格变化的宏观参数与浮石结构和化学的微观观察联系起来。该研究将(i)描述单一喷发口在单一时刻出现的火山岩碎片（火山碎屑）混合物的特征，（ii）对比岩浆组成、喷发风格和强度的广泛光谱的水泡和微岩结晶模式。火山碎屑中的大晶体和小晶体（分别为斑晶和微晶岩）和气泡（囊泡）“冻结”了岩浆房和管道中母批岩浆的历史，并代表了火山地下演化的“微观窗口”。我们将解释在喷发方式发生关键变化之前和之后，泡泡度和微晶结晶度的平均值和极值的变化。通过使用这些约束良好的历史喷发，我们期望这项工作的结果将广泛应用于记录较少的历史或史前喷发，并将大大提高我们对爆炸性火山活动期间喷发风格/强度突变的理解，并有助于预测维苏威火山（和其他锥状火山）下一次喷发的时间，而不是它将如何喷发，从危害管理和减轻的角度来看，这个问题同样重要。

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.