EAR-PF: A New Technique for Determining Eruption Timescales Applied to Large Igneous Provinces and Climatic Events over Earth History

本奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。Joseph Biasi被授予NSF EAR博士后奖学金，以研究火山爆发与地球生命历史之间的联系。火山爆发时，大量的二氧化碳、硫和火山灰会被释放到大气中，影响地球的气候。在某些情况下，火山爆发会在短短几天内向大气中释放大量气体，导致当地或全球气候的突然变化，有可能导致物种灭绝。然而，如果在几十年内释放出同样数量的气体，那么火山喷发对气候的影响就会小得多。科学家可以直接观察目前的活火山，并记录它们爆发需要多长时间；然而，没有关于史前火山爆发持续时间的记录。目前的项目扩展了Biasi博士之前的工作，即开发一种方法，利用火山的热量来确定过去喷发的持续时间。火山的管道系统（岩浆房、火山颈等）位于更古老的岩石中，岩浆通过这个管道系统会加热宿主岩石。长期喷发比短期喷发更能加热宿主岩石，因为有更多的时间将热量从岩浆传递到宿主岩石。比亚西博士将把这一原理应用于多个火山喷发，年龄从数千年到数亿年不等。这项研究将帮助我们了解过去火山爆发的影响，以及如何为未来的火山爆发做准备。在达特茅斯学院和俄勒冈大学进行这项研究时，Biasi博士将指导初级研究人员并授课。他还将开发地球科学课程计划、实验室和活动，供初中和高中教育者在课堂上使用。拟议中的研究将采用一种新技术，称为磁地热测量（MGT）。这种技术可以限制岩浆流过管道或流入侵入体的时间。在浅层侵入物（如补给堤）的情况下，MGT确定的时间尺度大致相当于喷发的时间尺度。MGT将烘烤接触测试（经典的古地磁技术）与热建模相结合，可以应用于年轻（1 Ma）和古老（2 Ga）的岩浆系统。MGT技术将应用于富兰克林LIP和哥伦比亚河洪水玄武岩的岩壁和堤防，这两者都与全球气候事件有关。之所以选择LIP，是因为LIP个别喷发的时间尺度几乎没有限制，而且还因为它们对地球历史的影响。最后，将MGT技术应用于山羊岩火山杂岩（侵蚀级联弧复合火山）。山羊岩的结果将作为“对照组”，并为LIP结果提供关键的比较点。通过将MGT结果与先前公布的挥发物含量和挥发物溶解度的估计相结合，我可以大致确定每次LIP喷发期间挥发物（CO2, H2S, SO2）的通量。这些挥发物通过全球变暖（CO2）或变冷（SO2）直接影响地球的气候和生物。这些结果将提供长期气候变化与大型火山爆发后推断的短期气候变化之间缺失的联系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Dr. Joseph Biasi has been awarded an NSF EAR Postdoctoral Fellowship to investigate the connections between volcanic eruptions and the history of life on this planet. During eruptions, large amounts of carbon dioxide, sulfur, and volcanic ash can be released into the atmosphere, affecting the earth’s climate. In some cases, eruptions release huge amounts of gases into the atmosphere in just a few days, causing a sudden change in local or global climate with the potential to cause the extinction of species. However, if that same amount of gas is released over a few decades, then the climate effects of the eruption will be much smaller. Scientists can directly observe currently active volcanoes and record how long they take to erupt; however, no records for durations of prehistoric volcanic eruptions exist. The current project expands on Dr. Biasi’s prior work to develop a method to determine the duration of past eruptions using heat from the volcano. The plumbing systems of volcanoes (magma chamber, volcanic neck, etc.) are hosted in older rocks, and the magma that passes through this plumbing system heats up the host rock. Long-lived eruptions heat up more host rock than short-lived eruptions because there is more time to transfer heat from the magma to the host rock. Dr. Biasi will apply this principle to multiple volcanic eruptions, ranging in age from thousands of years to hundreds of millions of years old. This research will help us understand how impactful volcanic eruptions were in the past, and how to prepare for future eruptions. While conducting this research at Dartmouth College and the University of Oregon, Dr. Biasi will mentor junior researchers and teach classes. He will also develop geoscience lesson plans, labs, and activities that middle- and high-school educators can use in their classrooms. The proposed research will employ a new technique, called magnetic geothermometry (MGT). This technique can constrain the amount of time that magma flowed through a conduit or fed an intrusion. In the case of shallow intrusives (such as feeder dikes) the timescales determined by MGT are roughly equivalent to the timescales of eruption. MGT combines the baked contact test (a classic paleomagnetic technique) with thermal modeling and can be applied to young (1 Ma) and old (2 Ga) magmatic systems. The MGT technique will be applied to sills and dikes of the Franklin LIP and the Columbia River flood basalts, both of which are associated with global climatic events. LIPs were chosen because there are few constraints on the timescales of individual LIP eruptions, and because of their impact on Earth History. Finally, the MGT technique will be applied to the Goat Rocks volcanic complex (an eroded Cascade arc composite volcano). Results from Goat Rocks will serve as a ‘control group’ and provide a crucial point of comparison for the LIP results. By combining the MGT results with previously published estimates of volatile content and volatile solubility, I can roughly determine the flux of volatiles (CO2, H2S, SO2) during individual LIP eruptions. These volatiles directly affect the Earth’s climate and organisms via global warming (CO2) or cooling (SO2). These results will provide the missing link between long-term climatic changes and short-term changes inferred to follow large eruptions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.