Causes and Consequences of Holocene Mafic Explosive Volcanism in Central OR

在过去的一万年里，俄勒冈中部一直是纽伯里火山和分布在俄勒冈中部喀斯喀特山脉的火山口喷发的地方。大多数火山喷发产生了玄武岩熔岩流和火山渣锥，人们怀疑许多火山喷发还产生了大量的喷发柱，这些喷发柱可能在大片地区散布少量的火山灰。作为俄勒冈州中部最大的城市，本德的人口自2000年以来增长了50%（目前人口约为75000人），而且本德位于喀斯喀特山脉的东部（顺风），建在纽贝里火山(指定为a ？非常高的威胁？因此，重要的是要了解产生火山灰的火山爆发可能对空中交通、娱乐和农业造成的潜在危害的范围。为了确保当地居民可以使用这项工作，他们将与美国地质调查局和美国林务局的科学家和口译员协调，翻译发现并改善与俄勒冈中部火山活动各方面相关的推广工作。为了改进俄勒冈中部的火山危害评估，有人建议研究几次不同喷发产生的沉积物，其中许多发生在过去的2000年里。具体来说，他们将对(1)北姊妹层状火山（Yapoah、Four-in-One和Collier Cone）北部的年轻岩屑锥进行测绘和取样；(2)年轻盾状火山Belknap Crater；(3)纽伯里火山最近的玄武岩喷发，大约在7000年前沿着其西北裂谷带喷发。目标之一是确定火山灰和矿渣沉积物的厚度和分布，因为它们构成了该地区未来喷发的主要危害，以及岩浆的挥发性（水和二氧化碳）含量，以确定上升岩浆的挥发性含量对喷发方式（爆炸性或喷涌性，即以火山灰沉积物或熔岩流为主）的控制程度。特别是，人们相信这项工作将提供对导致玄武岩岩浆爆发的条件的见解。另一个目标将是利用亚高山湖泊岩心研究更远的火山灰沉积物；这项工作将与地理系的同事合作，因为鉴定这些岩心中的火山灰沉积物将使他们能够评估过去2000年植物对火山爆发的反应。从整体上看，这项工作的独特之处在于，他们希望结合岩石学（通过研究岩浆挥发物和火山泥层结构）和物理火山学（通过研究火山泥层沉积物的性质）的方法，以形成推动单成因或小多成因岩浆喷发的岩浆系统的全面图景。

Central Oregon has been the site of numerous volcanic eruptions in the past 10,000 years from both Newberry Volcano and vents distributed throughout the central Oregon Cascades. Most of these eruptions have produced basaltic lava flows and cinder cones and it is suspected that many of the eruptions also created substantial eruption columns that could have distributed small amounts of volcanic ash over large regions. As the population of the largest city in central Oregon, Bend, has increased by 50% since 2000 (the population is currently ~ 75,000) and as Bend lies east (downwind) of the Cascades and is constructed on distal lava flows and scoria cones from Newberry Volcano (designated a ?very high threat? volcano by the USGS), it is important to understand the scope of potential future hazards posed by ash-producing eruptions that could affect air traffic, recreation, and agriculture. To insure that this work is available to local populations, they will coordinate with both U.S. Geological Survey and U.S. Forest Service scientists and interpreters to translate findings and improve outreach efforts related to all aspects of volcanism in central Oregon. To improve volcanic hazard assessment in central Oregon, it is proposed to study deposits produced by several different eruptions, many of which have occurred over the past 2000 years. Specifically, they will map and sample deposits from (1) young scoria cones north of North Sister stratovolcano (Yapoah, Four-in-One, and Collier Cone); (2) the young shield volcano Belknap Crater; and (3) the most recent basaltic eruptions of Newberry Volcano, erupted along its northwest rift zone about 7000 years ago. One of the goals is to determine both the thickness and distribution of ash and scoria deposits, as these pose the primary hazard from future eruptions in the region, and the volatile (water and carbon dioxide) content of the magma, to determine the extent to which the volatile content of the rising magma controls the eruptive style (explosive or effusive, that is, dominated by ash deposits or lava flows). In particular, it is believed that this work will provide insights into conditions that cause basaltic magma to erupt explosively. Another goal will be to study more distal ash deposits using sub-alpine lake cores; this work will be collaborative with colleagues from the Geography department, as identification of ash deposits in these cores will allow them to assess the vegetative response to eruptions over the past 2000 years. Taken as a whole, the proposed work is unique in its approach in that they hope to combine methods from petrology (by studying magmatic volatiles and tephra textures) and physical volcanology (by studying the nature of the tephra deposits) to develop of comprehensive picture of the magmatic systems that drive monogenetic or small polygenetic mafic eruptions.