Theories that propose feedbacks among climate, tectonics, and surface processes commonly assume that erosion is enhanced by glacial activity. Indeed, studies have shown that glaciers appear to limit the elevation of mountain ranges; however, comparisons between rates of glacial and nonglacial erosion are diffi cult to make. Ideally, such comparisons must hold precipitation and lithology constant, while only varying the erosional regime. Located in a climatic transition zone during the Pleistocene, the east-west-trending valleys of the Bitterroot Range present an opportunity for a quantitative analysis of glacial and nonglacial erosion because the north-facing sides of the valleys were glaciated, whereas the south-facing slopes were not. The different erosional regimes operating on either side of the valleys created strongly asymmetric ridges. Ridgelines separating the east-west-trending valleys have been pushed southward by glacial headwall retreat such that ridge-to-valley distances are ~50% greater on the north-facing slopes than on the south-facing slopes. In addition, mean hillslope angles are 6° lower on the glaciated slopes than on the unglaciated slopes, and calculations of geophysical relief suggest that, on average, glaciers have removed nearly twice as much rock as nonglacial processes. Finally, we conclude that, although rates of vertical incision by glacial processes in the Bitterroot Range were more rapid than nonglacial processes, the dominant geomorphological impact of glaciers was lateral erosion by headwall retreat.
9Thorough characterization of the spatiotemporal variability in soil thermal properties can 10 facilitate better designs for horizontal geothermal heat pump (HGHP) systems by reducing ground heat 11 exchanger (GHEX) costs. Results are presented from a new monitoring network installed across a range 12 of glaciated terrains in Indiana (USA), including the first known observations of the dynamic range of 13 thermal conductivity that occurs at the depth of horizontal GHEX installations. In situ thermal 14 conductivity data can vary significantly on a seasonal basis in coarse-grained outwash sediments (0.8-151.4 W m -1 K -1 ), whereas clay-and silt-dominated moraine sediments have a dampened seasonal range 16 within 10% of the annual mean. Thermal conductivity across the network ranges from 0.8 to 2.0 W m -1 17 K -1 depending on soil parent material, climatic setting, and particularly, soil-moisture variability. Results 18 indicate that the standard industry practice to estimate thermal properties from soil type often leads to 19 suboptimal GHEX design (i.e., GHEX design lengths were 44% to 52% longer than necessary to meet 20 performance specifications). This research suggests that expanding the characterization of soil thermal 21 properties in specific settings where HGHPs are targeted will improve understanding of the dynamic 22 aspects of ground heat exchange and lead to more optimal HGHP system designs. 23 Keywords: soil thermal properties, geothermal heat pump, thermal conductivity, ground temperature, 24 soil moisture 25 © 2015. This manuscript version is made available under the Elsevier user license
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