Geologic mapping of the northern plains of Mars, based on Mars Orbiter Laser Altimeter topography and Viking and Mars Orbiter Camera images, reveals new insights into geologic processes and events in this region during the Hesperian and Amazonian Periods. We propose four successive stages of lowland resurfacing likely related to the activity of near‐surface volatiles commencing at the highland‐lowland boundary (HLB) and progressing to lower topographic levels as follows (highest elevations indicated): Stage 1, upper boundary plains, Early Hesperian, <−2.0 to −2.9 km; Stage 2, lower boundary plains and outflow channel dissection, Late Hesperian, <−2.7 to −4.0 km; Stage 3, Vastitas Borealis Formation (VBF) surface, Late Hesperian to Early Amazonian, <−3.1 to −4.1 km; and Stage 4, local chaos zones, Early Amazonian, <−3.8 to −5.0 km. At Acidalia Mensa, Stage 2 and 3 levels may be lower (<−4.4 and −4.8 km, respectively). Contractional ridges form the dominant structure in the plains and developed from near the end of the Early Hesperian to the Early Amazonian. Geomorphic evidence for a northern‐plains‐filling ocean during Stage 2 is absent because one did not form or its evidence was destroyed by Stage 3 resurfacing. Remnants of possible Amazonian dust mantles occur on top of the VBF. The north polar layered deposits appear to be made up of an up to kilometer‐thick lower sequence of sandy layers Early to Middle Amazonian in age overlain by Late Amazonian ice‐rich dust layers; both units appear to have outliers, suggesting that they once were more extensive.

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Dams are socio‐ecological structures fundamentally serving human population growth and economic development. Yet, dams have significantly reduced landscape connectivity, altered hydrologic and geomorphic dynamics, and are a leading cause of freshwater biodiversity decline. As dams age and are no longer used for their original intended purpose, they increasingly threaten both humans and ecosystems. Consequently, dam removal is an increasingly accepted strategy to restore river systems across the United States; since the 1970s, more than 1,400 dams have been removed. As the removal trend continues, important decisions must be made regarding which dams are still ecologically and economically viable and which are optimal for removal to facilitate restoration and subsequent protection. Therefore, it is critical to prioritize dams for removal where rivers, freshwater resources, and ecosystem services will benefit most. To that end, this study uses geospatial analysis and a multi‐criteria decision framework to evaluate dams suitable for removal in the western United States in watersheds with existing conservation priorities, and to examine watershed dynamics in which they are situated. Results reveal 24 top‐ranked dams no longer performing essential ecological and social functions as optimal sites for removal to restore waterways. Of these top‐ranked dams, four are already in the planning process for removal, indicating the model is performing as intended. These results are critical for managers and policymakers to understand where dam removals could enhance overall riverine connectivity and where river restoration could result in subsequent protection of newly free‐flowing river segments in the National Wild and Scenic Rivers System.