Building volcanic ash records to date and correlate paleoenvironmental archives and improve volcanic histories

建立迄今为止的火山灰记录并关联古环境档案并改善火山历史

• 批准号: RGPIN-2018-04926
• 负责人: Jensen, Britta
• 金额: $ 2.55万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=654595
• 关键词: Building; volcanic; ash; records; date

Volcanic ashes (or tephra) are important for research reconstructing past environments and volcanic histories. Each tephra can be geochemically “fingerprinted” and dated, linking together the geologic records they were deposited in through space and time. Northwestern North America includes the Aleutian arc, the third most active volcanic arc in the world, and the less active, but more hazardous, Cascade arc. Surprisingly, tephra records for this region are underdeveloped, particularly for the most recent ~18,000 years. We are often missing critical data such as geochemistry, stratigraphy, age, and volcanic source. The overarching goal for my research program is to build a comprehensive volcanic record for NW North America that will inform both paleoenvironmental and volcanological studies. My proposal explores this long-term objective through these two themes:***Building tephra frameworks to date, correlate and interpret records of past climate: ***Understanding how and why Earth's climate is changing today requires us to understand the natural variability of climate in the past. This is particularly relevant to Canada as northern regions experience amplified climate change. Key data for reconstructing past climate can be found in annually laminated (varved) lake deposits from SW Alaska, Canadian arctic ice cores held in the Canadian Ice Core Archive, and Gulf of Alaska marine sediment cores. Tephra are essential for dating and correlating these deposits to help interpret their significance, but few have been studied. This proposal presents several projects that will study tephra within these deposits, integrating them with one another, while building towards the objective of developing a tephra framework for future paleoenvironmental studies.***Improving our understanding of volcanic processes and histories through tephra:***Tephra are a fundamental component in parsing past volcanic events, such as the magnitude and frequency of past eruptions, the underlying processes driving them, and their hazards to modern society. Data used to examine these questions are often gathered from deposits close to or on the volcanoes, but reoccurring eruptions and erosion often destroys this proximal evidence of past eruptions. Distal (>10 km from source) tephra help fill these gaps and develop more complete volcanic histories. This aspect of the proposal is fundamentally intertwined with the previous theme, but here I focus on how tephra in these deposits can help us understand eruption histories and dynamics. For this specific proposal I aim to address some fundamental problems that hinder our ability to use tephra in this manner. This includes refining geochemical techniques for tracing tephra to their volcanic source or region, and examining historical eruptions, such as the 1980 eruption of Mount St. Helens, to improve our interpretation of pre-historic eruptions through their geologic records.

火山灰（或火山灰）对于重建过去环境和火山历史的研究非常重要。每一个火山碎屑都可以通过地球化学的“指纹”和年代测定，将它们在空间和时间上沉积的地质记录联系在一起。北美西北部包括阿留申弧，世界上第三大活跃火山弧，以及不太活跃但更危险的喀斯喀特弧。令人惊讶的是，这个地区的火山灰记录是欠发达的，特别是最近的18,000年。我们经常缺少关键数据，如地球化学、地层学、年龄和火山源。我的研究计划的总体目标是建立一个全面的火山记录西北北美，将告知古环境和火山学研究。我的提议通过以下两个主题探讨了这一长期目标：*** 建立迄今为止的火山灰框架，关联和解释过去气候的记录：*** 了解今天地球气候如何变化以及为什么变化需要我们了解过去气候的自然变异性。这对加拿大尤其重要，因为北方地区的气候变化加剧。重建过去气候的关键数据可以在阿拉斯加西南部每年的层状（纹状）湖泊沉积物、加拿大冰芯档案中保存的加拿大北极冰芯和阿拉斯加湾海洋沉积物芯中找到。火山灰对于确定这些沉积物的年代和相互关联以帮助解释它们的意义是必不可少的，但很少有人研究过。该提案提出了几个项目，将研究这些矿床中的火山灰，将它们彼此结合起来，同时为未来的古环境研究建立火山灰框架。通过火山灰提高我们对火山过程和历史的理解：* 火山灰是解析过去火山事件的基本组成部分，例如过去火山爆发的规模和频率，驱动它们的潜在过程以及它们对现代社会的危害。用于研究这些问题的数据通常是从火山附近或火山上的沉积物中收集的，但重复发生的喷发和侵蚀往往会破坏过去喷发的近距离证据。远火山点（距离火山源>10公里）有助于填补这些空白，并形成更完整的火山历史。这方面的建议是从根本上交织在一起的前一个主题，但在这里我专注于如何火山灰在这些存款可以帮助我们了解喷发的历史和动力学。对于这个具体的建议，我的目标是解决一些基本的问题，阻碍我们以这种方式使用tephra的能力。这包括改进地球化学技术，以追踪火山灰的火山源或地区，并检查历史上的喷发，如1980年的圣海伦火山喷发，以改善我们通过地质记录对史前喷发的解释。