Document Type

Thesis

Abstract

Although the Appalachian mountains have been tectonically passive for approximately 180 million years, the range has the traits- high relief, steep slopes, incised tributary gorges, and regular mass wasting- of a tectonically active range. The conventional hypothesis posits that the mountains remain in a state of dynamic equilibrium, in which steady denudation at the surface occurs evenly throughout the landscape in combination with corresponding isostatic rebound, maintaining the relief. However, this hypothesis has been questioned by studies finding differential erosion rates on opposite sides of waves of knickpoints that appear to communicate a change in base level due to either climate change, drainage capture, or epeirogenic uplift. In this study, knickpoints were searched through the analysis of longitudinal profiles of tributaries in the Dan River, Smith River, and Mayo River basins, all watersheds located in the Blue Ridge Mountains of Virginia within the greater Roanoke River basin. Knickpoints were spatially clustered and found more frequently at higher elevations. In particular, migratory knickpoints were more common and likely to be at elevations of 500 - 800 meters, while the smaller number of stationary knickpoints were moderately skewed toward lower elevations. Given the marginal influence of lithology on the spatial placement of knickpoints, the landscape of the study region appears to be in disequilibrium, supporting the hypothesis of landscape disequilibrium causing the high relief characteristic of the Appalachians. However, the ultimate cause behind the nature the Appalachian landscape, whether driven by factors such as climate change or epeirogenic uplift, remains unknown.

Date Awarded

2015

Department

Geology

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