Date of Award
Master of Science (MS)
Environmental Engineering and Earth Science
Kelly Best Lazar
The critical zone (CZ) is the life sustaining outer layer of the earth that spans from the top of unweathered bedrock to the tops of the trees. This dynamic zone is always evolving because a variety of chemical, physical, and biological processes transform bedrock into regolith, creating a spatially heterogeneous CZ architecture. This study aims to investigate the relationships between regolith thickness, seismic velocities, and chemical profiles as a function of slope position and it is hypothesized bedrock composition, fracture density, and foliation are the key factors controlling the physical heterogeneity in the top 1-2 meters of the CZ. To test this hypothesis, seismic refraction tomography, structure from motion, and X-ray fluorescence (XRF) was used to quantify CZ structure across scales ranging from the 100s of meters to the 10s of centimeters in the Piedmont region of South Carolina. Seismic velocities track changes in structure (e.g. saprolite, fractured bedrock, and bedrock), while the role of bedrock composition was assessed using hand-held X-Ray fluorescence (XRF) XRF collected from two deep (>2 m) soil trenches. The seismic refraction and XRF data were integrated with three-dimensional models constructed using structure from motion (SFM). Results from the landscape sized seismic lines show significant depth to bedrock variability. Trench sized seismic lines show significant variations in depth to saprolite. Chemical data shows variations with depth expected in ultisol soil profiles as well as some variation suggesting preservation of bedrock features in the top few meters of the CZ.
Topping, Leah, "Quantifying Heterogeneity Along a Hillslope Using Seismic Refraction, Structure From Motion, and X-Ray Fluorescence in the Piedmont, South Carolina" (2023). All Theses. 4049.