CAREER: Tectonically dead but geomorphologically alive: Investigating the role of hard rocks as triggers of widespread, long-term landscape change in continent interiors

Though seemingly static to humans, watersheds – and the river networks they host – gradually and/or abruptly change configuration, growing, shrinking, and even disappearing over timescales of thousands to millions of years. River network reorganizations have remained enigmatic staples of landscapes in the interiors of continents for over a century. When far from any active geologic faults, little is known about what triggers them, how frequently they initiate, or how fast they evolve. In this project, the principal investigator will evaluate the hypothesis that resistant rocks near the outlets of rivers trigger and regulate the widespread river network reorganization in continent interiors. As human societies depend on water to develop and thrive, constraining the underlying regulators of past, current, and future distributions of rivers is fundamental to understanding the availability and sustainability of water resources on the Earth’s surface and subsurface. Through this project’s discoveries, the principal investigator will create an immersive, collaborative teaching initiative to train undergraduate and graduate students in topics and techniques of high environmental relevance. The work will foster the integration of scientific knowledge in higher education in the US, Brazil, and in collaborating high schools of the New York Metro area. Despite being in tectonically dead settings, landscapes in continent interiors are rife with evidence of drainage network reorganization and ongoing topographic change. Currently, no unifying mechanism systematically explains the spatial distribution, magnitudes, modes, and timing of drainage divide migration and river capture events in those landscapes. This research project will mechanistically link (i) rates of drainage divide migration and (ii) frequency-magnitudes of river capture events to lithologic changes of up to hundreds of kilometers downstream. The principal investigator’s research group will (i) constrain drainage area exchange rates between large neighboring drainage basins of the tectonically dead eastern Paraná Basin in southeast Brazil using cosmogenic nuclides, (ii) directly link those rates to basin-pair differences in rock properties (i.e. rock erodibilities, tensile, and compressive strengths), and (iii) integrate the empirical evidence with numerical modeling of landscape evolution using the Landlab library. Using this integrated Field + Laboratory + Numerical Modeling triad, the research results will systematically explain rates of drainage reorganization in continent interiors independent of external, hard-to-constrain triggers. Τhe project will also create a seamless doorway between scientific discovery and undergraduate education through scaffolded training opportunities in Quantitative Geomorphology. The activities will inspire and empower the participating, student populations to tackle environmental challenges. 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.