Collaborative Research: Landscape Evolution in the McMurdo Dry Valleys: Erosion Rates and Real-time Monitoring of Rock Breakdown in a Hyperarid, Subzero Environment

南极洲麦克默多干旱山谷地区是地球上最冷、最干燥、最多风的地方之一，经常被用来比较火星表面。它也是南极洲最大的无冰地区，因此它的沉积物和地貌包含了南极大陆其他地方或世界上无法获得的过去气候的独特记录。然而，为了准确地解释任何地质特征，我们必须了解它是如何形成和随时间变化的。特别是，在干旱的山谷里，我们对地球上最基本的地质现象之一--物理岩石破裂--的速度和原因了解很少。例如，干燥的山谷缺乏水分，这被认为是地球上大多数其他地方岩石破裂的关键因素。在这种看似惰性的环境中，是什么使岩石破碎？这个项目旨在通过“倾听”干燥山谷中岩石的破裂来回答这个问题。我们将在巨石上安装传感器，这些传感器充当微型地震仪，记录岩石上和岩石内部最微小的微破裂。同时，我们将监测岩石周围的天气和环境，以记录触发破裂事件的条件。在我们收集这些数据的同时，我们将从干燥山谷中不同年龄(从数千年到数百万年)的沉积物中收集岩石样本。对这些样品的测量将使我们能够看到岩石破裂的速度有多快，以及它们的特征如何随着地质时间的变化而变化。合并后的数据集将使未来的科学家能够更准确地了解南极洲，甚至可能是火星的古气候和地形。该项目还将在妇女人数仍然很少的领域为两名女性调查员提供支助。该项目还将为学生提供独特的接触和体验，范围从小学生到将直接从事项目各个方面工作的本科生和研究生。技术摘要麦克默多干燥山谷中的岩石经历了地球上一些最低的侵蚀速度。然而，我们目前对不同风化因素(湿度、冰冻温度、热循环、盐结晶或水化以及风蚀)在这些和其他环境中所起的相对作用的了解是有限的。此外，在干旱山谷，没有对风化和相关岩石侵蚀速率的变化进行系统评估，这些变化可能会随着空中暴露时间、岩性和质地的变化而发生重大变化。这项研究旨在(1)确定岩石破裂的主要驱动因素，(2)更好地量化侵蚀速率，(3)确定影响干旱山谷风化和侵蚀的岩性和环境因素。岩石破裂(破裂)将使用定制的声发射监测系统在就地巨石上实时记录。通过将声发射数据与岩石表面及其附近的微气象测量相结合，这项研究将在短时间(分钟到月)内直接测试与这种独特的极地沙漠气候下岩石破裂的环境驱动因素有关的假设。将使用宇宙成因核素技术，包括6种同位素(Be-10、Al-26、He-3、Ne-21、Cl-36、C-14)的新组合，以及岩石性质测量(例如，强度、弹性系数、热性质)，以阐明长期(KYR至MyR)巨石侵蚀率、岩性、岩石性质和空中暴露时间之间的复杂关系。通过将这些测量与声发射系统的短期破裂数据相结合，拟议的工作将彻底检查哪些岩性和环境因素以及颗粒尺度过程正在推动干旱山谷的地貌演变。通过限制巨石侵蚀速率并确定其对岩石性质和年龄的敏感性，结果将直接适用于该地区的宇宙成因核素暴露年龄研究。此外，由此得到的关于干燥山谷中风化过程及其与岩石形态的关系的信息可以用来解决关于火星上形成类似岩石形态的假设。项目调查员将参加由贡扎加大学运营的小学外展项目，该项目将支持一名本科生和研究生。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。

Non-technical AbstractThe McMurdo Dry Valleys region of Antarctica is one of the coldest, driest, and windiest places on the planet, and is often used as a comparison for the surface of Mars. It is also the largest ice-free region of Antarctica, and thus its deposits and landforms contain unique records of past climate not accessible elsewhere in the Antarctic continent or the world. In order to accurately interpret any geologic feature, however, we must understand how it forms and changes through time. In particular, in the Dry Valleys, we have a poor understanding of the rates and causes of one of Earth's most fundamental geologic phenomenon - physical rock breakdown. For example, the Dry Valleys lack moisture, which is thought to play a key role in rock breakdown in most other locations on the planet. What serves to fracture rocks in this seemingly inert environment? This project aims to answer that question by 'listening' as rocks crack in the Dry Valleys. We will instrument boulders with sensors that act as miniature seismographs, recording even the smallest microcracking on and within the rocks. At the same time, we will monitor the weather and environment around the rocks to record the conditions that trigger cracking events. While we collect these data, we will gather rock samples from deposits of different ages (from thousands to millions of years old) in the Dry Valleys. Measurements on these samples will allow us to see how quickly rocks breakdown and how their characteristics change over geologic time. The combined datasets will allow future scientists to more accurately understand the paleoclimates and landscapes of Antarctica, and possibly even Mars. This project will also serve to support two female investigators in a field where women are still largely underrepresented. The project will also provide unique exposure and experience to students, ranging from elementary students to the undergraduate and graduate students who will be working directly on various aspects of the project. Technical AbstractRocks in the McMurdo Dry Valleys experience some of the lowest erosion rates on Earth. However, our current understanding of the relative role that different weathering factors (moisture, freezing temperatures, thermal cycling, salt crystallization or hydration, and wind abrasion) play in these and other environments is limited. Further, in the Dry Valleys, there has been no systematic evaluation of the variance in weathering and associated rock erosion rates, which may change significantly as a function of subaerial exposure duration, lithology, and texture. This research seeks to (1) characterize the primary drivers of rock breakdown, (2) better quantify erosion rates, and (3) determine the lithological and environmental factors that influence weathering and erosion in the Dry Valleys. Rock breakdown (cracking) will be recorded in real-time on in situ boulders using a custom acoustic emission monitoring system. By coupling acoustic emission data with micrometeorological measurements at and near rock surfaces, this study will directly test hypotheses relating to the environmental drivers of rock breakdown under this unique polar desert climate over short (minute to monthly) timescales. Cosmogenic nuclide techniques including a novel combination of 6 isotopes (Be-10, Al-26, He-3, Ne-21, Cl-36, C-14) together with rock property measurements (e.g., strength, elastic moduli, thermal properties) will be used to elucidate the complex relationship between long-term (kyr to Myr) boulder erosion rates, lithology, rock properties, and subaerial exposure duration. By synthesizing these measurements with short-term cracking data from the acoustic emission system, the proposed work will thoroughly examine which lithological and environmental factors and grain-scale processes are driving geomorphic evolution in the Dry Valleys. By constraining boulder erosion rates and determining their sensitivity to rock properties and age, the results will be directly applicable to cosmogenic nuclide exposure age studies in this region. Additionally, the resulting information on weathering processes and their relationship to rock morphology in the Dry Valleys can be used to address hypotheses as to formation of similar rock morphologies on Mars. The Project Investigators will participate in an elementary school outreach program run by Gonzaga University, and the project will support an undergraduate and graduate student.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.