Geology Club Seminar

Ridgelines, defined here as along-ridgetop topographic profiles of drainage divides from near a basin's outlet to its furthest headwaters, occur across almost every landscape on Earth and other rocky planets, yet, surprisingly, these features have received almost no study from the geomorphology community. For over a century, geomorphologists have analyzed rivers, hillslopes and even hilltops to infer the tectonic and climatic history of the landscape, but this idea has not been explored for ridgelines. I propose that ridgelines may also encode information about climate, tectonics, and lithology in a manner analogous to river longitudinal profiles (the latter of which has been the subject of thousands of papers over decades of geomorphic research, whereas the former has yet to be explored).

In this talk, I will focus on the ability of ridgelines to record tectonic forcing. I begin by developing a theoretical framework for ridgeline morphology and then test the theoretical predictions against ridgelines from analog experiments and observations from natural landscapes. Results from my analyses identify a characteristic ridgeline morphology and show that, below a threshold uplift rate near 1 mm yr-1, the slope of ridgelines, normalized for basin area, becomes steeper with increasing uplift rates. My results indicate the transition from fluvial to debris-flow dominated channel networks causes the thresholding of ridgeline slope.

In this talk, I describe a new technique for inferring uplift rates from ridgeline morphology. This approach can be combined with other uplift proxies to increase confidence in predictions and refine estimates of adjustment timescales in transient landscapes responding to tectonic forcing. This work marks a first step in ridgeline research, which—if even a fraction as effective as river analysis—could significantly advance our understanding of the dynamic interactions between tectonics, climate, and topography.