Investigating the tectonic geomorphology of the Santa Ynez Mountains, CA and developing middle school geoscience lessons

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Nutt, Mara

Issue Date

2023

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Thesis

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geomorphology , outreach , teaching , tectonics

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The understanding of how topography responds to tectonic and climatic forcingsto shape landscapes (1) and engaging young people in the geosciences (2) are the two focuses of my thesis. First, I discuss my tectonic geomorphology work in the Santa Ynez Mountains, CA (SYM), then my work planning, teaching, evaluating, and publishing a pair of lessons about rock weathering I taught to ~300 middle schoolers. The tectonic geomorphology project is being prepared for publication, and my outreach work has been accepted to the National Science Teachers Association’s Magazine ‘Science Scope’. The SYM is a case study landscape in which climate is held constant while tectonic and lithologic forcings vary. Compiling past thermochronology and marine terrace exhumation/uplift rate data in addition to new cosmogenic radionuclide erosion rates, we analyze the spatial and temporal changes in uplift/erosion in the SYM. The relief of the SYM reflects the million-year timescale exhumation rate gradient from west to east, while more recent active faulting is impacting marine terrace uplift rates on the order of 50 thousand years. Erosion rates from CRN are an order of magnitude lower than exhumation/uplift rates, and do not show any trend with topography or exhumation/uplift rates. Additionally, our topographic analysis shows that relative channel steepness and mean hillslope angle increase along the west east transect, with rock strength controlling smaller scale steepness and gradients. This study shows that while topography does respond to variation in tectonic forcing and rock strength, the timescales of response can vary. In middle school classrooms we taught students about rock weathering, both with respect to impacts on long term climate and soil formation through hands on experiments. Lesson 1 has students investigate how changing the temperature and acidity of weathering agents affects the rate of rock weathering of sandstone and limestone (using sugar cubes and chalk, respectively, as models) and if the products of weathering different rock types impact the climate on geologic timescales by adding CO2 to the atmosphere or not. Lesson 2 focuses on how weathering impacts our day to day lives. Students perform experiments simulating how bedrock weathering of different rock types (mudstone and granite) occur at different rates, produce different small particles, and interact with weathering agents differently. These lessons bring rock weathering into the classroom with cross cutting concepts and connect the earth, climate, and human society together in an interactive way.

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