RUI: Rapid Variation of the Geomagnetic Field in Reversal: Evidence from the Sheep Creek Range, North Central Nevada

RUI：地磁场反转的快速变化：来自内华达州中北部羊溪山脉的证据

• 批准号: 0409684
• 负责人: Scott Bogue
• 金额: $ 12.89万
• 依托单位: Occidental College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409684&HistoricalAwards=false
• 关键词: RUI; Rapid; Variation; Geomagnetic; Field

The goal of this study is to determine whether the unusual magnetism of two lava flows in the Sheep Creek Range (north central Nevada) resulted from extremely rapid (i.e., degrees/day) geomagnetic field change during a polarity reversal. In both flows, rock near the flow base, magnetized relatively early as the flow cooled, has a remanence direction similar to the lava flow directly below. Rock from the interior of the flow, presumably the last to cool and become magnetized, has a remanence direction much closer to the overlying flow. A similar pattern in a lava flow from Steens Mountain (Oregon), also magnetized during a geomagnetic polarity reversal, has been interpreted as evidence that the field was changing as fast as several degrees per day as the flow was cooling. Field change this rapid cannot be reconciled with commonly accepted ideas about deep-earth properties and processes.The primary activity of this research will be a detailed paleomagnetic and rock magnetic study of samples to be collected on closely spaced vertical profiles through the two flows. The goal will to be fully characterize vertical changes in magnetization direction and inferred ancient field intensity and to determine whether rapid field change or some remagnetization process preferentially affecting the flow interiors can better explain the changes. The conclusion will depend strongly on whether there exists a correlation between rock magnetic properties and remanence direction consistent with the hypothesis of preferential remagnetization.The broader impacts of this project are twofold. The first is to provide research opportunities to at least 5 Occidental College students over the next 3 years. Research is an integral part of the undergraduate program at Occidental College and the centerpiece of each student's experience as a geology major. In addition, this research will contribute toward an understanding of what future generations might experience in the not-to-distant future if (as some believe) the geomagnetic field is in the early stages of a polarity reversal. Knowledge of transitional field behavior in the geologic past can provide a rational basis for anticipating and adapting to an environment that will be different in significant ways from the one we live in now.

这项研究的目的是确定羊溪山脉（内华达州中北部）两股熔岩流的异常磁性是否是由于极其快速的（即，度/天）的地磁场变化。在这两个流动，岩石附近的流动基地，磁化相对较早的流动冷却，有一个剩磁方向类似的熔岩流直接下方。 来自流动内部的岩石，大概是最后冷却并被磁化的，其剩磁方向更接近上覆流动。来自俄勒冈州的斯蒂恩斯山（Steens Mountain）的熔岩流也有类似的模式，在地磁极性反转期间也被磁化，这被解释为磁场变化的证据，即当熔岩流冷却时，磁场变化的速度高达每天几度。磁场变化如此之快，与人们普遍接受的关于地球深部性质和过程的看法是不一致的，这项研究的主要活动将是对通过两股水流在间隔很近的垂直剖面上收集的样品进行详细的古地磁和岩石磁学研究。我们的目标将是充分表征磁化方向的垂直变化和推断古磁场强度，并确定是否快速的磁场变化或一些再磁化过程优先影响流内部可以更好地解释的变化。 这一结论将在很大程度上取决于岩石磁性和剩磁方向之间是否存在与优先再磁化假设相一致的相关性。首先是在未来3年内为至少5名西方大学生提供研究机会。研究是西方学院本科课程的一个组成部分，也是每个学生作为地质学专业经验的核心。 此外，这项研究将有助于了解如果（正如一些人所认为的那样）地磁场处于极性反转的早期阶段，后代在不远的将来可能会经历什么。 了解过去地质时期的过渡场行为，可以为预测和适应一个与我们现在生活的环境有很大不同的环境提供一个合理的基础。