Collaboration with Prof. Chris Poulsen, University of Michigan. Topography in mountainous regions is a product of the erosion and export of material across the landscape. The frequency and magnitude of erosion events occurring in these regions is controlled by the local climate. The topography of the mountain ranges, in turn, influences the climate. This suggests a coupling between atmospheric and geomorphic processes in regions of active mountain building. Observational studies of climate-topography-erosion relationships, however, have been equivocal. One potential reason for this disparity in observational results is that the modern climate, for which most studies depend on, is a poor representation of the integrated climate history over landscape. Over the timescale of mountain building, climate can vary due to orbital variations, greenhouse gas concentrations, and the development of topography. This work will develop a coupled climate-landscape evolution model framework to quantitatively investigate interactions between climate, topography, and erosion on geologic timescales. The co-evolution of climate and landscapes will be modeled at different latitudes (e.g. tropical, sub-tropical, and mid-latitude) and for different orbital configurations in order to increase our understanding of the spatial and temporal variability inherent in the coupled climate and landscape systems. This work will complement previous and ongoing empirical studies exploring the interaction of climate and topography.
This project will quantify how differences in rock strength result in changes in channel morphology of bedrock streams, providing a potential method to remotely map rock strength from observations of channel morphology. The field area is in a natural experiment in central Arizona where streams flow over a wide range of rock types and exhibit significant changes in morphology. The project will provide insight into why and how rock strength influences bedrock erosion processes and morphology at the reach scale. Measurements of channel morphology and characteristics will be compared to quantitative estimates of rock strength. Additionally, a series of controlled laboratory experiments using a flume in collaboration with Elowyn Yager and a rock fatigue apparatus in collaboration with S.J. Jung will quantify the susceptibility of the different rock types to abrasion and damage accumulation. The results of the proposed work will result in quantitative relationships between channel morphology and rock strength. Moreover, because of the focus on understanding why and how rock strength influences reach scale channel morphology, we will develop a quantitative framework for predicting rock strength from channel morphology in locations beyond our field site.
In addition to local controls on channel morphology, as mentioned above in the central Arizona project, lithology can influence the rate of landscape transience over longer, geologic time and space scales. In this project, we seek to understand how lithology influences landscape evolution and transience over geologic timescales. Preliminary work suggests that the Salmon River incised a deep (~1.2 km) gorge starting at about 9 million years ago. This gorge cuts through a number of different rock types, sending off waves of transients into the surrounding landscapes. The rate at which these knickzones propagate is being controlled by the local lithology. We are quantifying the rate of knickpoint propagation and the rock mass properties that control the erosional resistance. The results will inform numerical models of landscape evolution on typical ranges of erodibility values and what rock mass properties dictate the resistance.
Photo above: transient river in Idaho. Hyperactive Laborador for scale.
Rivers in mountainous landscapes are influenced by two fundamental properties of its environment: (1) the rate of vertical baselevel fall, which is driven by rock-uplift and (2) the supply of coarse, bedload sediment from upstream hillslope processes. Our work uses natural experiments in diverse places such as tropical Taiwan and southern Peru to quantify how bedrock rivers evolve. We estimate rates of erosion using cosmogenic nuclides and optically stimulated luminescence. Field-work and GIS analysis are used to measure channel width and slope. These data provide great insights into the interaction between sediment supply and the morphology of the river. We use these data to inspire and inform new numerical models that quantify river evolution over a range of timescales and provide insight into the tectonic environments in which they evolve.
How do landslides and sediment transport influence basin wide erosion rates estimated by cosmogenic nuclides? Specifically, how do pulses of landslide activity, from events such as earthquakes or large, rare storm events imprint the cosmogenic nuclide inventory, and how long do these impacts last? Answering this requires estimates of landslide sizes and information on the transport capacity of the fluvial system.
Another question our group purses related to geochronology techniques is: how do landscape dynamics influence thermochronology age distributions?
How can we quantify glacial erosion over long time scales?
What impact do glaciers have on both the local topography and topography downstream of maximum glaciations?
dr. brian yanites
department of earth and
1001 e. 10th st.
bloomington in 47405