RUI: Reconstructing ancient terrestrial landscapes of the southeastern Columbia Basin

随着地质年代的变化，水、风和火山活动重塑了地球表面。在华盛顿州东南部，今天的景观反映了两个难以想象的事件：巨大的熔岩喷发和更晚的冰河时代的特大洪水，它们冲刷并重塑了景观。该项目关注这两个事件之间缺失的间隔，并利用古代土壤来了解这些古代景观形成时的环境。12名本科生将参与研究经验，其中将包括在地球科学中广泛使用的现场和实验室技术。本研究的目的是描述华盛顿州东南部和俄勒冈州东北部哥伦比亚河玄武岩喷发后的陆地环境，并重建形成该地区景观的地质过程。这将通过建立一个横跨哥伦比亚盆地东南部的野外站点网络来完成，这些站点将暴露出风化的玄武岩接触层和古土壤。在每个地点，接触物和下面的玄武岩的形态将被表征，样品将被收集用于实验室分析微观形态特征和散装化学丰度。熔岩流在整个地区以不同的海拔暴露出来，从而可以研究降水梯度及其对玄武岩风化的影响，并测量暴露时间或热成岩作用造成的成土差异。这些分析将提供以下能力：(1)更好地了解喀斯喀特抬升的时间和随后哥伦比亚盆地的干旱化；(2)重建冰河时期爆发洪水造成的地形，这些洪水发生在最近的冰河时期洪水之前；(3)区分原始土壤风化和埋藏后的过程。这项研究将增加对太平洋西北地区复杂构造的理解，并为特大洪水对陆地景观形成的影响提供见解。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。

Landscapes change over geological time as water, wind, and volcanic activity reshape Earth’s surface. In southeastern Washington State, today’s landscape reflects two events of unimaginable size: mammoth eruptions of molten lava and much later, Ice Age mega-floods that scoured and reshaped the landscape. This project focuses on the missing interval between these two events and uses ancient soils to learn about the environment when these ancient landscapes formed. Twelve undergraduate students will be engaged in research experiences that will incorporate field and laboratory techniques that are in wide use in the geosciences.The goal of this research is to characterize terrestrial environments following the eruption of the Columbia River Basalts in southeastern Washington and northeastern Oregon, and to reconstruct the geological processes that shaped the landscape in this area. This will be accomplished by creating a network of field sites across the southeastern Columbia Basin that expose weathered basalt contacts and paleosols. At each site the morphology of the contact and underlying basalt will be characterized, and samples will be collected for lab analyses of micromorphological features and bulk chemical abundances. Lava flows are exposed throughout the region at different elevations, allowing for the study of precipitation gradients and their influence on basalt weathering, and to measure differences in pedogenesis caused by exposure time or thermal diagenesis. These analyses will provide the ability to (i) better understand the timing of Cascade uplift and the subsequent aridification of the Columbia Basin, (ii) reconstruct the landforms caused by periods of glacial outburst flooding that predate the most recent Ice Age floods and (iii) distinguish original soil weathering from post-burial processes. This research will increase understanding of the complex tectonics of the Pacific Northwest and provide insights into the impact of megafloods in shaping the terrestrial landscape.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.