Constraints on the tempo and magnitude of explosive volcanism: facilitating long-term ash fall hazard assessments

对爆发性火山活动的速度和强度的限制：促进长期火山灰坠落危险评估

• 批准号: MR/Y011767/1
• 负责人: Paul Albert
• 金额: $ 75.48万
• 依托单位: Swansea University
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FY011767%2F1
• 关键词: Constraints; tempo; magnitude; explosive; volcanism

Explosive volcanic eruptions have devastating impacts in near-vent areas where pyroclastic density currents can cause significant loss of life, yet the injection of large volumes of ash into the atmosphere and its subsequent dispersal over hundreds to thousands of kilometres, pose significant and far-reaching hazards. Ash fall is a severe and wide-ranging volcanic hazard; causing roof collapse, health (respiratory) and agricultural issues and wide-scale interruptions to essential infrastructure. Even ash emitted during moderately explosive eruptions can ground air traffic as was demonstrated by the 2010 Eyjafjallajökull eruption (Iceland). As such widespread volcanic ash dispersals present huge economic and societal costs. Disturbingly, 800 million people live within 100 km of active volcanoes globally, yet statistical studies of global eruption databases indicate significant under-recording of past volcanic eruptions deeper in time. For instance, this analysis would indicate up to 66% of VEI 5 eruptions, equivalent in scale to the 1980 Mount St Helens eruption, are missing within the geological record spanning the last 200,000 years. Our understanding of the magnitude and frequency of eruptions at a particular volcano is typically skewed to recent activities, because records of older eruptions are fragmentary often owing to erosion and/or burial by more recent eruptions. The better-preserved, shorter-term records, however, do not necessarily reflect the full range of volcanic activity, or variations in the tempo of activity. This is a major obstacle for long-term volcanic hazard assessments and hampers our ability to: i) determine changing eruption-rates through time, ii) evaluate magnitude-frequency relationships and iii) project the recurrence intervals of hazardous ash dispersals. This research has overcome this impasse by reconstruct comprehensive long-term records of explosive volcanism for volcanoes in southern and central Japan. This research exploits the under-utilised record of volcanic ash layers preserved in dense networks of marine and lake sediment cores away from the volcano. These continuous sediment sequences present unprecedented repositories of ash fall (preserved as visible and microscopic deposits), which are not susceptible to destructive near-source volcanic processes. Using state-of-the-art chemical 'fingerprinting' techniques, it is possible to pinpoint the volcanic source of the distal ash layers, whilst tracing these ash fall events across a network of cores provides the opportunity to computationally model and map past ash dispersals, and calculate eruption magnitudes. Integrating cutting-edge dating techniques (40Ar/39Ar/14C) to date the ash deposits, enables us to reveal the timing and tempo of past explosive eruptions at an individual volcano, and importantly determine the recurrence intervals of widespread hazardous volcanic ash dispersals from these volcanoes. Our research in south and central Japan has been successfully tackling eruption un-reporting and plugged the gaps in the eruption records of numerous volcanoes. In the next phase of our research we will expand the application of our methods to address the volcanoes of NE Japan and the Kurile Arc, utilising newly available marine cores from International Ocean Discovery Programme (IODP) and Japan Agency For Marine-Earth Sciences and Technology (JAMSTEC). In addition, using our ability to produce comprehensive eruption records, we will explore volcano-climate interactions. The distal volcanological records generated in this project will continue to be examined in partnership with those directly responsible for volcanic hazard assessments at individual volcanoes, and policy-makers working in the field.

爆炸性火山喷发在近火山口地区造成毁灭性影响，火山碎屑密度流可造成重大的生命损失，但大量灰烬注入大气并随后扩散到数百至数千公里，造成重大而深远的危害。火山灰降落是一种严重而广泛的火山灾害；造成屋顶坍塌、健康（呼吸）和农业问题，并使基本基础设施大面积中断。就像2010年Eyjafjallajökull火山喷发（冰岛）所证明的那样，即使是在中度爆炸性喷发期间排放的火山灰也可以使空中交通中断。如此广泛的火山灰扩散带来了巨大的经济和社会成本。令人不安的是，全球有8亿人居住在活火山100公里以内，然而，对全球火山爆发数据库的统计研究表明，对过去更深时间的火山爆发的记录严重不足。例如，这一分析将表明，在过去20万年的地质记录中，高达66%的VEI 5级喷发（相当于1980年圣海伦火山喷发的规模）是缺失的。我们对某座火山喷发的规模和频率的理解通常是偏向于最近的活动，因为较早的喷发记录是碎片化的，通常是由于最近的喷发的侵蚀和/或掩埋。然而，保存较好的短期记录并不一定反映火山活动的全部范围或活动速度的变化。这是长期火山危险评估的一个主要障碍，妨碍了我们以下方面的能力：1)确定随时间变化的喷发率，2)评估震级-频率关系，3)预测危险火山灰扩散的复发间隔。这项研究通过重建日本南部和中部火山爆发活动的全面长期记录，克服了这一僵局。这项研究利用了未被充分利用的火山灰层记录，这些记录保存在远离火山的密集的海洋和湖泊沉积物岩心网络中。这些连续的沉积物序列呈现出前所未有的灰烬落库（以可见和微观沉积物的形式保存），它们不容易受到破坏性的近源火山作用的影响。使用最先进的化学“指纹”技术，可以精确定位远端火山灰层的火山来源，同时通过岩心网络追踪这些火山灰坠落事件，为计算模型和绘制过去的火山灰扩散图提供了机会，并计算出喷发的震级。结合先进的年代测定技术（40Ar/39Ar/14C）对火山灰沉积物进行年代测定，使我们能够揭示单个火山过去爆发爆发的时间和速度，并重要地确定这些火山广泛的危险火山灰扩散的复发间隔。我们在日本南部和中部的研究已经成功地解决了火山喷发未报告问题，并填补了许多火山喷发记录的空白。在我们研究的下一阶段，我们将利用国际海洋发现计划（IODP）和日本海洋地球科学技术机构（JAMSTEC）新获得的海洋岩心，扩大我们的方法在解决日本东北部和千岛岛弧火山问题上的应用。此外，利用我们生产全面喷发记录的能力，我们将探索火山与气候的相互作用。本项目产生的远端火山学记录将继续与在个别火山直接负责火山危害评估的人员和在实地工作的决策者合作进行审查。