Quantifying Physical Characteristics and Weathering of Bedrock in Relation to Landscape Development in the Colorado Front Range
Horne, Alexandra Michelle
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Bedrock weathering is a fundamental component of critical zone geomorphology that can be influenced by rock strength, fracture spacing, mineralogy, and topoclimate. By quantifying rock strength, we can characterize bedrock weathering across a landscape and interpret its influence on the evolution of local geologic features, such as tors. This study measured the compressive strength and fracture characteristics of bedrock throughout the Boulder Creek watershed to assess the degree of weathering. Test sites included glacially polished and adjacent weathered alpine bedrock, weathered tors and saprolite in areas of lower elevation, and several highway road exposures. The data collected shows an inversely proportional relationship between depth/degree of weathering and the compressive strength of bedrock. Once bedrock begins to weather, it weakens to an intermediate range of compressive strength, and with increased chemical and physical weathering becomes the weakest local rock measured. At lower elevations, structural anisotropy, microclimate, and regolith removal are the dominant forces governing tor location, size, and differential weathering.