Formation, morphology, and retreat of autogenic waterfalls

地球的地形是由构造板块的运动(构造地形)和气候(侵蚀地形)共同塑造的。因此，气候或构造的变化可以记录在微妙的地形变化中。例如，在构造断层穿过河流的地方，断层运动的变化可能会导致瀑布的形成。这些瀑布可以在景观中保留数千到数百万年，使地质学家能够利用瀑布的存在和位置来推断地球历史上过去的变化。然而，最近的研究表明，即使在气候和构造强迫保持不变的情况下，瀑布也可能自发形成。因此，使用瀑布从景观中读取地球历史需要区分自形成的瀑布和那些在气候或构造变化后形成的瀑布。这个项目试图区分这样的瀑布，从而从根本上提高我们破译地球历史上过去变化的能力。除了这一科学进展之外，该项目还将通过利用人们对瀑布的敬畏之心，通过创建在线视频和K12课堂访问，重点关注山溪灾害和瀑布形成，促进公众对地球科学的兴趣。该项目还将支持两名女性早期科学家的博士和硕士项目，并为本科生提供培训。该项目的目标是研究瀑布自形成(或自生形成)的机制，以及自形成瀑布的形态和侵蚀率。这将通过实验室实验、实地工作和建模的组合来实现。实验室水槽实验将测试自生瀑布形成的条件，这些结果将与现有的基岩台阶发展理论以及将作为项目一部分收集的假定自生瀑布的大型数据库进行比较。实验室和现场工作将允许开发定量的、无量纲度量来识别现场的自生瀑布，并将允许评估自然界中自生瀑布的普遍存在。最后，这些结果将被应用于建立一个解释自生瀑布形成和撤退的河流长剖面演变模型，并可用于预测景观对自生动力和外部扰动的耦合响应。因此，该项目填补了关于自生过程如何改变基岩地貌的基本知识空白，从而增强了我们‘阅读’记录在地形图中的地球历史记录的能力。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Earth’s topography is sculpted by both the movement of tectonic plates (which build topography) and climate (which erodes topography). As such, changes in climate or tectonics can be recorded in subtle topographic variations. For example, where tectonic faults cross rivers, changes in fault movement can lead to waterfall formation. These waterfalls can remain in landscapes for thousands to millions of years, allowing geologists to use the presence and position of waterfalls to infer past changes in Earth history. However, recent work has suggested that waterfalls may also spontaneously self-form, even when climate and tectonic forcing remains constant. Therefore, using waterfalls to ‘read’ Earth history from landscapes requires distinguishing self-formed waterfalls from those that form following changes in climate or tectonics. This project seeks to distinguish such waterfalls, thereby fundamentally improving our ability to decipher past changes in Earth history. Beyond this scientific advance, the project will promote public interest in the Earth sciences via harnessing the awe of waterfalls to engage in community outreach through the creation of online videos and K12 classroom visits focused on mountain stream hazards and waterfall formation. The project will also support the PhD and masters project of two female early-career scientists, as well as provide training for undergraduate students. The goal of this project is to investigate the mechanisms by which waterfalls can self-form (or form autogenically), as well as the morphology and erosion rates of self-formed waterfalls. This will be accomplished through a mix of laboratory experiments, field work, and modeling. Laboratory flume experiments will test the conditions under which autogenic waterfalls form, and these results will be compared to existing theory for the development of bedrock steps as well as a large database of putative autogenic waterfalls that will be collected as part of the project. The lab and field work will allow development of quantitative, non-dimensional metrics to identify autogenic waterfalls in the field, and will allow assessment of the ubiquity of autogenic waterfalls in nature. Finally, these results will be applied to develop a river long profile evolution model that accounts for autogenic waterfall formation and retreat, and can be used to predict the coupled response of landscapes to autogenic dynamics and external perturbations. This project thus fills a fundamental knowledge gap on how autogenic processes modify bedrock landscapes, thereby enhancing our ability to ‘read’ the record of Earth history recorded in topography.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.