The role of bedrock erodibility in the topography and landscape evolution of the Appalachian Mountains

基岩侵蚀性在阿巴拉契亚山脉地形和景观演化中的作用

• 批准号: 2333215
• 负责人: James Spotila
• 金额: $ 34.22万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-02-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2333215&HistoricalAwards=false
• 关键词: role; bedrock; erodibility; topography; landscape

Mountains linger on the continents long after they are built by tectonic motions. During their erosional decay, these diminishing mountains are subject to modification by changing conditions, including climate, basin dynamics, and renewed tectonics, resulting in complex signals. Another factor that controls the evolution of these landscapes is the material properties of the eroding bedrock, which change through time as rocks are exhumed. Correlations exist between topography and rock type in many ancient mountain ranges, including in the Appalachian Mountains, the type locality of this phenomenon. In sedimentary rocks of the Appalachians, the role of bedrock properties is at least qualitatively clear, but in metamorphic rocks the relationships are murkier. The purpose of this investigation is to determine the degree to which metamorphic rocks of the high Blue Ridge control the landscape and to quantify specifically what makes them durable. This will contribute to understanding of the origin of the Appalachian landscape, as well as to the processes that control erodibility along ancient passive margins. This project also supports a program for developing and adding a field experience as a required element for eighth grade Earth Science classes in a rural Appalachian middle school (~350 students/year), where currently no field trips are included in the curriculum. The specific goals of this project are to measure bedrock properties of complex metamorphic rock of the Virginia and North Carolina Blue Ridge, including rock strength (e.g., point-load testing), discontinuities (e.g., fracture scanlines), mineralogy, and sensitivity to chemical and physical surface processes via laboratory testing (freezing/thawing, heating/cooling, microwave acid digestion, and slake testing). A large data collection effort (~150 locations, 500 samples) will fill a major data gap for the material properties of complex Blue Ridge rock types. Samples will be acquired from both natural and anthropogenic exposures and will be compared to relative topographic position (i.e., ridges and peaks vs. valley bottoms) as well as a host of other geomorphic metrics. Data will be synthesized to test the degree to which bedrock controls topography and ultimately be integrated into a model of what controls long-term erodibility in this setting.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.

山脉在构造运动形成后很长一段时间内仍然在大陆上徘徊。在侵蚀衰退过程中，这些不断缩小的山脉会受到气候、盆地动态和新构造等条件变化的影响，从而产生复杂的信号。控制这些景观演变的另一个因素是侵蚀基岩的物质特性，随着岩石的挖掘，这些物质特性会随着时间的推移而发生变化。在许多古代山脉中，地形和岩石类型之间存在相关性，包括阿巴拉契亚山脉，即这种现象的典型产地。在阿巴拉契亚山脉的沉积岩中，基岩性质的作用至少在定性上是清楚的，但在变质岩中，这种关系则更加模糊。这项调查的目的是确定蓝岭高处的变质岩对景观的控制程度，并具体量化是什么让它们经久耐用。这将有助于了解阿巴拉契亚景观的起源，以及控制沿古代被动边缘的侵蚀性的过程。该项目还支持一项计划，该计划旨在开发和增加实地经验，作为阿巴拉契亚乡村中学（每年约 350 名学生）八年级地球科学课程的必修内容，目前该学校的课程中不包括实地考察。 该项目的具体目标是测量弗吉尼亚州和北卡罗来纳州蓝岭复杂变质岩的基岩特性，包括岩石强度（例如点载荷测试）、不连续性（例如裂缝扫描线）、矿物学和化学敏感性通过实验室测试（冷冻/解冻、加热/冷却、微波酸消解和熟化测试）进行物理表面处理。大量数据收集工作（约 150 个位置，500 个样本）将填补复杂蓝岭岩石类型材料特性的主要数据空白。样本将从自然和人为暴露中获取，并将与相对地形位置（即山脊和峰顶与谷底）以及许多其他地貌指标进行比较。数据将被合成，以测试基岩控制地形的程度，并最终整合到控制该环境中长期侵蚀性的模型中。该奖项反映了 NSF 的法定使命，并通过使用基金会的知识进行评估，被认为值得支持。优点和更广泛的影响审查标准。