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

Non-technical Abstract

The 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 Abstract

Rocks 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.