Causes and Consequences of Holocene Mafic Explosive Volcanism in Central OR

在过去的10,000年里，俄勒冈州中部发生了多次火山喷发，这些火山来自纽伯里火山和分布在俄勒冈州中部喀斯喀特地区的喷口。这些喷发中的大多数都产生了玄武岩熔岩流和煤渣锥，人们怀疑许多喷发还产生了大量的喷发柱，可能会将少量火山灰分布在大片地区。由于本德是俄勒冈州中部最大的城市，自2000年以来人口增加了50%(目前人口约为75,000人)，本德位于瀑布以东(顺风)，建造在纽伯里火山(被指定为非常高的威胁？)的远端熔岩流和斯科石锥上。由于火山喷发(由美国地质勘探局提供)，重要的是了解产生火山灰的喷发可能影响空中交通、娱乐和农业的未来潜在危险的范围。为了确保当地居民能够获得这项工作，他们将与美国地质调查局和美国林业局的科学家和翻译协调，翻译调查结果，并改进与俄勒冈州中部火山活动各个方面相关的外联工作。为了改进俄勒冈州中部的火山危险性评估，有人建议研究几次不同喷发产生的沉积物，其中许多喷发发生在过去2000年。具体地说，他们将绘制北姐妹层状火山(Yapoah，Four-in-One，Collier Cone)北部年轻的斯科里亚圆锥体的地图并取样；(2)年轻的盾形火山贝尔克纳普陨石坑；(3)纽贝里火山最近的玄武岩喷发，大约7000年前沿着其西北裂谷地带喷发。其中一个目标是确定火山灰和火山渣沉积的厚度和分布，因为它们构成该区域未来喷发的主要危险，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(爆炸性或热液性，即以火山灰沉积或熔岩流为主)的控制程度。特别是，人们相信这项工作将为玄武岩岩浆爆炸喷发的条件提供洞察力。另一个目标将是利用亚高山湖泊岩心研究更多的远端火山灰沉积；这项工作将与地理系的同事合作，因为识别这些岩芯中的火山灰沉积将使他们能够评估过去2000年来火山喷发的植被反应。总的来说，这项工作的独特之处在于，他们希望将岩石学(通过研究岩浆挥发和火山灰结构)和物理火山学(通过研究火山灰矿床的性质)的方法结合起来，全面描绘驱动单成因或小型多成因镁铁质喷发的岩浆系统。

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.