A New Look at Landslides of the Vermilion and Echo Cliffs, Northern Arizona
Abstract
The Vermilion and Echo Cliffs form a nearly continuous escarpment more than 160 km long within the Colorado Plateau physiographic province of North America. The cliffs overlie the Marble Platform in northern Arizona and are located along the Colorado River, just upstream of the Grand Canyon. Large rotational block landslides mantle the erosional escarpment along most of its extent. Although these landslides have been noted for over 100 years, their likely origin has never been explained. Landslide failure surfaces appear to be influenced by the Petrified Forest Member of the Triassic Chinle Formation, a shale layer containing smectite clay weathered from volcanic ash. Although landslides are common along the majority of escarpments comprising the Colorado Plateau where the Petrified Forest Member and other shales outcrop, most appear to have been inactive since the early Holocene. Multiple generations of landslides and remnants of previous slides exist up to 3 km from the present cliff face. Multiple working hypotheses explaining these landslides are explored in this article, including past landslides and/or lava dams along the Colorado River within the Grand Canyon, periods of wetter climate with higher groundwater levels, and earthquakes related to nearby faulting and volcanism. Various sliding modes along these cliffs are described along with potential triggering mechanisms. Back-analysis of these landslides has been conducted using mechanical properties of the formations involved as well as varying groundwater levels. Calculated factors of safety for existing slides under present conditions are greater than unity, consistent with their apparent stability.
Recommended Citation
C. M. Watkins and J. D. Rogers, "A New Look at Landslides of the Vermilion and Echo Cliffs, Northern Arizona," Environmental and Engineering Geoscience, vol. 28, no. 2, pp. 173 - 192, Geological Society of America, May 2022.
The definitive version is available at https://doi.org/10.2113/EEG-D-21-00063
Department(s)
Geosciences and Geological and Petroleum Engineering
Keywords and Phrases
Arizona; Block Kinematics; Colorado River; Erosion; Factor of Safety; Geomorphology; Geotechnical Strength Parameters; Landslides; Rock Mechanics; Slope Stability; Toreva Blocks
International Standard Serial Number (ISSN)
1558-9161; 1078-7275
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2022 Geological Society of America, All rights reserved.
Publication Date
01 May 2022
Comments
This study was made possible through funds provided by the Hasselmann Endowment of the Department of Geosciences, Geological and Petroleum Engineering, and the Natural Hazards Mitigation Institute at the Missouri University of Science and Technology. We are also thankful for support from the Norman R. Tilford Field Studies Scholarship, 2005, which also assisted in funding this research.