Super-eruptions, Eruptive Centers and Time-volume Behavior of a Continental Hotspot: The Central Snake River Plain

最大和潜在最具破坏性的火山喷发类型被称为超级喷发。这类事件是人类经验之外的事情，但可以肯定的是，它们将在未来发生。尽管公众对这些罕见但具有潜在破坏性的事件有所了解，但对它们的最终起源、直接原因和环境影响的基础研究还很匮乏。在北美，过去1600万年来最多产的超级喷发来源是蛇河平原-黄石热点地区，从爱达荷州西南部和内华达州北部一直延伸到黄石公园本身。该地区最强烈的事件发生在12-9 Ma之间，流纹岩的喷发约为10,000-20,000千米3(作为参考，1980年的圣海伦斯火山喷发只涉及不到1千米3的岩浆)。在这次爆发中喷发的岩浆是高温流纹岩，这是一种不同寻常的岩浆类型，在过去被忽视了，直到现在才被彻底研究，关于它的起源和在大喷发期间的行为。也许这些岩浆及其喷发方式最重要的方面是任何一次事件所涉及的岩浆的绝对体积，这在很大程度上决定了环境影响的程度。只有通过对野外火山单元的详细测绘才能重建火山喷发的这一方面和其他方面，这是一项需要经验丰富的研究人员全职关注的困难项目。因此，这个项目将资助一名博士后研究人员，他将负责将不同的岩石露头联系在一起，以建立单位对比和体积，并使用这些数据来确定蛇河平原中部流纹岩喷发的数量和频率。这项工作还将涉及矿物和化学分析以确定单个单位的指纹，以及放射性测年以确定绝对年龄。所有这些信息将与新的和现有的岩石学数据一起用于约束流纹岩岩浆的成因和储存史。这些结果将有助于我们了解重大火山活动(最终是由地幔异常高的热流驱动)期间的地球大陆地壳，并为评估下一次此类事件可能造成的环境破坏程度提供基础。

The largest and potentially most devastating types of volcanic eruptions are known as super-eruptions. Such events are outside human experience, yet it is quite certain that they will occur in the future. Despite some public awareness of these rare but potentially devastating events, there is a shortfall of basic research into their ultimate origins, immediate causes, and environmental impacts. In North America, the most prolific source of super-eruptions for the past 16 million years has been the Snake River Plain-Yellowstone hotspot trace, stretching from SW Idaho and northern Nevada to Yellowstone itself. The most intense episode in this region occurred between ~12 and 9 Ma, with the eruption of the order of 10,000 - 20,000 km3 of rhyolite (for reference, the 1980 eruption of Mount St. Helens involved less than 1 km3 of magma). The magmas erupted during this flare-up were high-temperature rhyolites, an unusual type of magma that has been somewhat neglected in the past and only now is being thoroughly studied with respect to its origin, and behavior during large eruptions. Perhaps the most important aspect of these magmas and the way they erupt is the sheer volume of magma involved in any one event, which largely determines the magnitude of the environmental impact. This and other aspects of the eruptions can only be reconstructed through detailed mapping of volcanic units in the field, a difficult project that requires the full-time attention of an experienced researcher. Therefore, this project will fund a post-doctoral researcher who will be charged with tying together different rock outcrops to establsh unit correlations and volumes, and to use these data to establish the volume and frequency of rhyolitic eruptions from the central Snake River Plain. The work will additionally involve mineral and chemical analysis to fingerprint individual units, and radiometric dating to establish absolute ages. All this information will be used constrain genesis and storage history of the rhyolitic magmas in conjunction with new and existing petrologic data. The results will help inform our understanding of Earth's continental crust during major episodes of volcanism (ultimately driven by unusually high heat flux from the mantle), and provide a basis for assessing the degree of enviromental disruption that might be expected from the next such event.