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Glacial isostatic adjustment directed incision of the Channeled Scabland by Ice Age megafloods

Pico, Tamara and David, Scott R. and Larsen, Isaac J. and Mix, Alan C. and Lehnigk, Karin and Lamb, Michael P. (2022) Glacial isostatic adjustment directed incision of the Channeled Scabland by Ice Age megafloods. Proceedings of the National Academy of Sciences of the United States of America, 119 (8). Art. No. e2109502119. ISSN 0027-8424. PMCID PMC8872708. doi:10.1073/pnas.2109502119.

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During the last deglaciation, dozens of glacial outburst floods—among the largest known floods on Earth—scoured the Channeled Scabland landscape of eastern Washington. Over this same period, deformation of the Earth’s crust in response to the growth and decay of ice sheets changed the topography by hundreds of meters. Here, we investigated whether glacial isostatic adjustment affected routing of the Missoula floods and incision of the Channeled Scabland from an impounded, glacial Lake Columbia. We used modern topography corrected for glacial isostatic adjustment as an input to flood models that solved the depth-averaged, shallow water equations and compared the results to erosion constraints. Results showed that floods could have traversed and eroded parts of two major tracts of the Channeled Scabland—Telford-Crab Creek and Cheney–Palouse—near 18 ka, whereas glacial isostatic adjustment limited flow into the Cheney–Palouse tract at 15.5 ka. Partitioning of flow between tracts was governed by tilting of the landscape, which affected the filling and overspill of glacial Lake Columbia directly upstream of the tracts. These results highlight the impact of glacial isostatic adjustment on megaflood routing and landscape evolution.

Item Type:Article
Related URLs:
URLURL TypeDescription Information CentralArticle
Pico, Tamara0000-0002-3629-0922
David, Scott R.0000-0002-7925-7452
Larsen, Isaac J.0000-0003-3094-4830
Mix, Alan C.0000-0001-7108-3534
Lehnigk, Karin0000-0001-7239-3913
Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY). Edited by Thomas Dunne, Bren School of Environmental Science and Management, University of California, Santa Barbara, CA; received May 26, 2021; accepted December 15, 2021. T.P. acknowledges funding from the NSF-EAR (Division of Earth Sciences) Postdoctoral Fellowship and the University of California President’s Postdoc Fellowship. M.P.L and I.J.L. acknowledge support from a collaborative NSF grant (1529110 and 1529528). K.L. acknowledges support from an NSF Graduate Research Fellowship. Data Availability: Source data for this research, including hydrodynamic modeling data, GIA-corrected topographic reconstructions, and analysis scripts, are publicly available on Zenodo ( Source data have been deposited in Zenodo ( All other study data are included in the article and/or SI Appendix. Author contributions: T.P., I.J.L., A.C.M., and M.P.L. designed research; T.P. performed research; S.R.D. and K.L. contributed new reagents/analytic tools; T.P. analyzed data; and T.P. and M.P.L. wrote the paper. The authors declare no competing interest. This article is a PNAS Direct Submission. This article contains supporting information online at
Funding AgencyGrant Number
University of CaliforniaUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:Channeled Scabland; glacial isostatic adjustment; erosional history
Issue or Number:8
PubMed Central ID:PMC8872708
Record Number:CaltechAUTHORS:20220215-959810500
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Official Citation:Glacial isostatic adjustment directed incision of the Channeled Scabland by Ice Age megafloods. Tamara Pico, Scott R. David, Isaac J. Larsen, Alan C. Mix, Karin Lehnigk, Michael P. Lamb. Proceedings of the National Academy of Sciences Feb 2022, 119 (8) e2109502119; DOI: 10.1073/pnas.2109502119
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113450
Deposited By: Tony Diaz
Deposited On:15 Feb 2022 18:14
Last Modified:25 Feb 2022 16:50

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