Surface Morphology of Pyroclasts from Mount St. Helens and Vesuvius: Characterization and Interpretation

该项目将开发和测试一种方法， 形态特征的识别与分析 结晶玻璃状幼年火山碎屑 火山碎屑沉积：1）1980年圣海伦火山的产物， 公元79年维苏威火山的沉积物。 广泛的 从火山泥流到普利尼亚福尔斯的沉积物都是由这两个 事件 两个矿床的地层和喷发现象 已经被很好地研究和表征。 初级晶粒表面形态的集体特征将是 根据字符的连续变化来解释 这两次爆发的原因。 机械的相对影响和 谷物表面的化学过程将通过 火山灰的喷发、搬运、沉积和冷却。 每个主要地层的足够的火山碎屑数据集 将检查这些沉积物的水平，以确定关键结构 对解释环境历史很有用。 在 此外，还将进行实验研究， 在水中淬火的热碎片的形态，和织构 通过在专门设计的 设备. 火山碎屑形态学研究方法的发展 用计算机调查和验证结果 分析是这项研究的组成部分。 各种技术 用于火山灰形态的分析， 最适合确定沉积物历史的 从单个组件的特性。

This project will develop and test a methodology for the identification and analysis of morphological features on crystalline and glassy juvenile tephra from two calssic pyroclastic deposits: 1) the 1980 products of Mount St. Helens, and 2) the A.D. 79 deposits of Vesuvius. A wide range of deposits from lahars to plinian falls were produced by these two events. The stratigraphy and eruptive phenomena of both deposits have been well studied and characterized. Collective features of primary grain-surface morphology will be interpreted in terms of the successive changes in the character of these two eruptions. The relative effects of mechanical and chemical processes on grain surfaces will be traced through the eruption, transportation, deposition and cooling of the tephra. Data sets of sufficient pyroclasts from every major stratigraphic level of these deposits will be examined to identify key textures useful for interpretation of environmental histories. In addition, experimental studies will be done to investigate the morphology of hot fragments quenched in water, and the textures produced by abrasion of primary clasts in a specially designed device. Development of a methodology for pyroclast morphologic investigation and verification of the results using computer analysis are integral parts of this study. Various techniques for analysis of tephra morphologies will be tested to determine which are best suited to determine the history of the deposits from the characteristics of the individual components.