The Eureka Valley Landslide: Evidence of a Dual Failure Mechanism for a Long-Runout Landslide

Abstract

Long-runout landslides are well-known and notorious geologic hazards in many mountainous parts of the world. Commonly encompassing enormous volumes of debris, these rapid mass movements place populations at risk through both direct impacts and indirect hazards, such as downstream flooding. Despite their evident risks, the mechanics of these large-scale landslides remain both enigmatic and controversial. In this work, we illuminate the inner workings of one exceptionally well-exposed and well-preserved long-runout landslide of late Pleistocene age located in Eureka Valley, east-central California, Death Valley National Park. The landslide originated in the detachment of more than 5 million m3 of Cambrian bedrock from a rugged northwest-facing outcrop in the northern Last Chance Range. Its relatively compact scale, well-preserved morphology, varied lithologic composition, and strategic dissection by erosional processes render it an exceptional laboratory for the study of the long-runout phenomenon in a dry environment. The landslide in Eureka Valley resembles, in miniature, morphologically similar “Blackhawk-like” landslides on Earth, Mars, and minor planet Ceres, including the well-known but much larger Blackhawk landslide of southern California. Like these other landslides, the landslide in Eureka Valley consists of a lobate, distally raised main lobe bounded by raised lateral levees. Like other terrestrial examples, it is principally composed of pervasively fractured, clast-supported breccia. Based on the geologic characteristics of the landslide and its inferred kinematics, a two-part emplacement mechanism is advanced: (1) a clast-breakage mechanism (cataclasis) active in the bedrock canyon areas and (2) sliding on a substrate of saturated sediments encountered and liquefied by the main lobe of the landslide as it exited the main source canyon. Mechanisms previously hypothesized to explain the high-speed runout and morphology of the landslide and its Blackhawk-like analogs are demonstrably inconsistent with the geology, geomorphology, and mineralogy of the subject deposit and its depositional environment.

Structural Relationships Across the Sevier Gravity Slide of Southwest Utah and Implications for Catastrophic Translation and Emplacement Processes of Long Runout Landslides

“…Along the slide transport parallel profile, the SGS upper plate consists of numerous mountain‐sized blocks of intact volcanic rocks with boundaries defined by variations in stratigraphy, bedding attitude, structures, and overall damage state. Broadly, the upper plate displays a high degree of internal coherency that preserves the original and upright, though attenuated and damaged, stratigraphic succession like megabreccias described in smaller volcanic landslides (e.g., Legros et al., 2000; Pollet & Schneider, 2004; Schneider & Fisher, 1998; Shaller et al., 2020). Near the basal contact, the upper plate is intensely fractured into rock and crystal fragments by jigsaw fractures and along anastomosing shear fractures (Figures 4a, 5e and 10).…”

“…Lower plate Brian Head Formation is generally undisturbed, except for local jigsaw‐style fractured clasts immediately beneath the contact and sheared clasts at the slide surface (Figure 5d). Jigsaw fractures, characterized by intense fracturing with minimal rotation and disarticulation of fragments leaving a fitted fabric to damaged clasts, are commonly observed in volcanic debris‐avalanche deposits (Shaller et al., 2020; Shreve, 1968; Malone, 1995). Bedding in the underlying Brian Head Formation remains subhorizontal.…”

Landslide mechanism and stability of an open-pit slope: The Manglai open-pit coal mine

“…A single-stage traction landslide caused by snow melting can evolve into a multi-stage rotary landslide (Wang et al, 2020a;Xie et al, 2020). Perennial loading or rainfall infiltration at the back edge of a sliding mass can easily lead to thrust load-caused landslides (Yong et al, 2013;Zhang M. et al, 2015), as well as composite landslides, under the action of coupling factors (Cheng and Luo, 2010;Yang et al, 2012;Shaller et al, 2020). Although these studies add to our knowledge of the landslide mechanism, they only internal and external factors.…”

Development Trend and Stability Analysis of Creep Landslide With Obvious Slip Zone Under Rainfall-Taking Xinchang Xiashan Basalt Slope as an Example

“…A variety of methods based on elastic-plastic theory and the application of improved limit equilibrium methods emerge as times require. In particular, people try to use the finite element method to study the stability of slope, which creates conditions for the quantitative evaluation of landslide stability and makes it gradually transit to the numerical method (Kaya and Midili, 2020;Shaller et al, 2020).…”