Collaborative Research: The Lake Superior basin: Natural geomorphic experiment, deepwater-terminating ice stream, and isostatically adjusting rift

Glaciers, lakes, rivers, and the solid Earth interact to reshape the surface environment. This applies to the Lake Superior Basin, a basin that formed as a rift in Earth's crust 1.1 billion years ago and since has hosted mountains, lakes, glaciers, rivers, and human inhabitants. Past and present lake-level change is responding to ancient ice-sheet retreat, whose unweighting of Earth's surface causes our planet's crust to bend and underlying mantle to flow.

This project takes a multidisplinary approach to better understand the shaping of this continental landscape. The research team is reconstructing how the geological past of the Lake Superior basin impacts ongoing uplift and tilting of the land surface as well as surface processes including river erosion. Lake-level fall incites rivers to slice downwards through sediment and rock, while lake-level rise drowns the river mouths, causing deposition of gravel and sand.

Mapping the three-dimensional patterns of the rivers encompassing the Lake Superior Basin, as they cut through materials ranging from soft mud to hard rock, is critical for understanding erosional processes. Additionally, dating landforms associated with past water-terminating glaciers and simulating their dynamics using computer models will improve scientists' ability to predict the fate of Earth’s existing ice sheets.

Indigenous Ojibwe partners will consult in the research and share knowledge of both land and lake. Through a partnership with the Superior Hiking Trail Association, the project team will enhance outdoor recreation by providing public scientific knowledge of the region and its natural history. Finally, the research team is self-examining its approaches and practices to learn how to better include and support upcoming generations of Earth scientists.

Through the nexus of the Lake Superior basin, this research is answering fundamental questions about river incision, (de)glacial landscape and lake-scape evolution, water-terminating glacier instabilities, and glacial isostatic adjustment. Lake Superior provides a uniquely suited testbed to advance each of these knowledge areas and to understand their feedbacks.

Synchronous base-level fall on Lake Superior triggered river incision and knickpoint propagation across myriad lithologies, providing replicate natural experiments in erosional mechanics. The project team is applying traditional glacial geological approaches together with state-of-the-art topographic analyses to map lake-level evolution and the extent of glacial and fluvial process domains.

Paleolake shorelines and spillways were modified by, and record, glacial isostatic adjustment, which can be further constrained via detailed seismic imaging of three-dimensional solid-Earth structure and extensive modern global navigation satellite system data. These data are being used to probe deeply into the mechanisms and feedbacks surrounding the marine ice sheet instability, critical for understanding the response and sensitivity of marine-terminating outlet glaciers and ice sheets.

The research team is partnering with local nonprofit and government organizations to share the narrative of the Lake Superior region, integrate Indigenous knowledge, and build an inclusive field-research program whose goal is to invite a diversifying next generation into the geosciences

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.