T126 Showcase of Undergraduate Research Posters by 2YC and 4YCU Geoscience Students (Posters)

Monday, 10 October 2022
2:00 PM - 6:00 PM
Exhibit Hall F

THE HERMOSA CLIFFS OF SW COLORADO: AN ANALYSIS OF MASS WASTING MECHANISMS AND HAZARDS

Paper number: T126-25
Program: Technical Sessions
Time: 2:00 PM – 6:00 PM

Authors

Abstract

In the US, landslides cause over $1 billion in damage and over 25 deaths each year. Landslide hazards in a particular region require careful mapping, attention to the local geology, hydrology, and topography, and analysis of past landslide activity. Here we present progress on such an effort for an iconic stretch of cliffs located in southwestern Colorado. Along the “Million Dollar Highway” north of Durango, CO, is an imposing 15-mile, ~2000-ft high escarpment known as the Hermosa Cliffs. Although 1:24,000 Geologic mapping from 2004 identified deposits from 12 large landslides along the foot of the Hermosa Cliffs, development has progressed into and around those deposits. Fire-related debris flows coming off the Hermosa Cliffs in 2018 caused millions of dollars in property damage. And as development expands into the region on and near these large slide deposits, it is important to have a clear understanding of the specific hillslope hazards presented by the escarpment.

We used a combination of fieldwork and analysis of new USGS LiDAR data for the region (including surface roughness and slope), to re-map all quaternary deposits along the foot of the cliffs as a 1:10,000-scale ‘strip’ map. Relative ages of deposits were determined through analysis of cross-cutting relationships, surface roughness, and soil development. As part of that mapping, we distinguish among six types of deposits and their associated processes 1) larger, deep-seated landslides that appear to be generally older, 2) larger, more fluid landslides 3) rock avalanches of various age, 4) colluvial aprons below steep cliff faces, 5) alluvial fans constructed by debris flow and frequent channel avulsion, and 6) young, smaller slumps from the material on top of the cliffs. Together, these processes present a range of hazards to development below the cliffs. Further work will be required to determine whether any of the landslide deposits have been reactivated in recent centuries, but the mapping presented has already helped to refine the specific spatial patterns of the aforementioned hillslope hazards.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-381800

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.