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Pediments of the Sonoran Desert in the United States have intrigued physical geographers and geomorphologists for nearly a century. These gently sloping bedrock landforms are a staple of the desert landscape that millions visit each year. Despite the long-lived scientific curiosity, an understanding of the processes operating on the pediment has remained elusive. In this study we revisit the extensive history of pediment research. We then apply geospatial, field, and laboratory cosmogenic10Be nuclide dating and back-scattered electron microscopy methods to assess the pace and processes of landscape change on pediment systems abutting the Salt River in Arizona. Our study focuses on the Usery pediments linked to base-level fluctuations (river terraces) of the Salt River. Relict pediment surfaces were reconstructed with dGPS data and kriging methodologies utilized in ArcGIS—based on preserved evidence of ancient pediment surfaces.10Be ages of Salt River terraces established a chronology of incision events, where calculating the volume between the reconstructed relict pediment and modern surface topography established minimum erosion rates (∼41 mm/ka to ∼415 mm/ka). Pediment area and length appear to have a positive correlation to erosion rate and development of planar pediment surfaces. Field and laboratory observations reveal that pediment systems adjust and stabilize at each Salt River terrace. Relief reduction across the pediment begins with pediment channel incision via headward erosion. Next, tributary drainage capture begins and collapses interfluves. Lateral stream erosion promotes planation where the porosity of decayed granite along channel banks exceeds the bedrock underneath ephemeral channels. [ABSTRACT FROM PUBLISHER]

The role of President John Quincy Adams (1825-29) as a patron of the arts and as the person responsible for the sculptural program of the United States Capitol has largely gone unnoticed. Adams had studied more works of art than any other president before him, and his knowledge of the arts was at least equal to that of Jefferson. In 1825, when a competition for the design of the main pediment of the Capitol yielded no acceptable proposal, Adams--at first involuntarily--got involved in the design process and eventually determined the features of a pediment celebrating the American Constitution. No ancient or modem models existed on which Adams and his advisors could have drawn. While classical forms prevail, their iconography is uniquely American, emphasizing a relationship between the individual figures that is allegorical and literal--and consequently difficult to read and easily misunderstood. Adams was aware of that fact and suggested an explanatory inscription that was never carried out. Crawford's pediment for the Senate wing of the Capitol overcame the problems facing Adams by discarding allegories and concentrating on "telling a story." [ABSTRACT FROM AUTHOR]