We measured 10 Be in fluvial sediment samples (n ‫؍‬ 27) from eight Great Smoky Mountain drainages (1-330 km 2). Results suggest spatially homogeneous sediment generation (on the 10 4-10 5 yr time scale and Ͼ100 km 2 spatial scale) at 73 ؎ 11 t km ؊2 yr ؊1 , equivalent to 27 ؎ 4 m/m.y. of bedrock erosion. This rate is consistent with rates derived from fission-track, long-term sediment budget, and sediment yield data, all of which indicate that the Great Smoky Mountains and the southern Appalachians eroded during the Mesozoic and Cenozoic at ϳ30 m/m.y. In contrast, unroofing rates during the Paleozoic orogenic events that formed the Appalachian Mountains were higher (Ն10 2 m/m.y.). Erosion rates decreased after termination of tectonically driven uplift, enabling the survival of this ancient mountain belt with its deep crustal root as an isostatically maintained feature in the contemporary landscape.

We use in situ‐produced and meteoric 10Be, analyzed in soils from 28 pits on four hillcrest‐parallel transects along a 14° hillslope in the Great Smoky Mountains, North Carolina, as tracers of soil production and transport. We rely upon amalgamation both to investigate and smooth spatial variability in 10Be concentrations. Lidar indicates that the hillslope is topographically complex and that soil is moved downslope diffusively until it encounters the ephemeral channel network and is rapidly exported. In situ‐produced 10Be, measured in depth profiles, indicates that over millennial timescales, soils are mixed above the soil‐saprolite boundary. In contrast, meteoric 10Be concentrations increase with depth and are correlated to concurrent increases of dithionite‐extractable Al and pH, observations explained by similar Al and Be mobility in the soil. The concentrations of both meteoric and in situ‐produced 10Be increase downslope proportional to the maximum soil particle path length. The data suggest virtual downslope soil velocities of 1.1–1.7 cm yr−1 in a well‐mixed active transport layer ∼60 cm thick. The thickness of this transport layer is constant downslope and depends on the rooting depth and consequent root wad thickness of downed trees on the slope, both of which reflect depth to the soil/saprolite boundary. Both meteoric and in situ‐produced 10Be suggest that soil production is balanced by surface denudation at rates between 10 and 13 m Myr−1. Soil residence times on the slope range from 21 to 33 kyr based on the meteoric 10Be inventories. Major element geochemical analysis suggests little if any elemental loss during soil transport downslope.

The direct and secondary effects of rapidly changing climate caused large rivers draining the Atlantic passive margin to incise quickly into bedrock beginning about 35,000 years ago. Measured in samples from bedrock fluvial terraces, 10-beryllium shows that both the Susquehanna and Potomac Rivers incised 10- to 20-meter-deep gorges along steep, convex lower reaches during the last glacial cycle. This short-lived pulse of unusually rapid down-cutting ended by 13,000 to 14,000 years ago. The timing and rate of downcutting are similar on the glaciated Susquehanna and unglaciated Potomac Rivers, indicating that regional changes, not simply glacial meltwater, initiated incision.