Blocky Hillslopes: From Outcrops to Flatirons

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

A nontechnical description of the project that explains the signficance and importance The majority of earth's land surface consists of hillslopes, but current mathematical models of hillslope evolution fail to capture many of the key elements of real landscapes. Most hillslopes, especially in mountainous and arid terrain, are rough and rocky. The goal of this project is to advance knowledge of how such common rocky hillslopes evolve through time. The landscape near Boulder, Colorado, serves as a natural experiment in which several rocky landforms can be used to test conceptual and quantitative models of rocky hillslope evolution. This project will test the hypothesis that all hillslope features can be simulated by numerical model that is based upon the differences in the density and orientations of the fractures that bound the blocks. This project will increase knowledge of how common landscapes evolve by acknowledging the roles played by the type of rock being eroded and the degree of fracturing of that rock. These qualities are important in evaluating the controls on landslides and other slope movements and can help in the evaluating risks from natural hazards. The project has a very strong education and outreach component that will develop the topic for various audiences, including undergraduate students, science teachers, and the general public. A technical description of the project Current models of landscape evolution fail to capture the key elements of real landscapes. This project is designed to test to what degree a single model utilizing the same rule set can reproduce the features of various rock types and orientations. This new suite of models will illuminate erosional hillslope processes in rocky terrain, and allow quantitative exploration of how these patterns arise. Research will include both fieldwork and numerical modeling. Fracture distributions, geometry of block edges in outcrop, block sizes in talus, and locations of trees capable of prying out blocks will be documented in the field and on imagery from digital elevation models. Cosmogenic isotope analyses will constrain local rates of erosion. A hierarchy of numerical models will be developed and constrained by the field measurements. The project builds upon a long-standing partnership with the education outreach program of the University of Colorado Division of Continuing Education, "Science Discovery." An existing curriculum that focuses on streams will be augmented by materials that illustrate local hillslopes and their evolution. These curricular materials will also be demonstrated to middle school teachers who participate in a week-long teacher training workshop each summer. Presentations will be also designed for teenagers interested in science through a monthly evening "Teen Cafe" series held in Boulder, and for local retirement communities. The broader history of landscape evolution discovered through this project will be meshed with evolution of the iconic landforms of the Boulder area that local residents see out their windows.