Magnitude and Timing of the Tiltill Rockslide in Yosemite National Park, California

2021 ◽  
Vol 27 (4) ◽  
pp. 395-407
Author(s):  
Christopher J. Pluhar ◽  
Kiersti R. Ford ◽  
Greg M. Stock ◽  
John O. Stone ◽  
Susan R. Zimmerman
Keyword(s):  
Sierra Nevada ◽  
National Park ◽  
Rock Slope ◽  
Yosemite National Park ◽  
Fault Rupture ◽  
Triggering Mechanism ◽  
Long Runout ◽  
Coulomb Failure ◽  
Triggering Mechanisms ◽  
Eastern Sierra Nevada

ABSTRACT Yosemite National Park, California, is one of the best-documented sites of historical rockfalls and other rock slope failures; however, past work shows that this record does not capture the infrequent largest occurrences, prehistoric events orders of magnitude larger than the largest historic ones. These large prehistoric events are evident as voluminous bouldery landslide deposits, permitting volume and age quantification to better understand local volume–frequency relationships, potential triggering mechanisms, and the hazard such events might pose. The Tiltill rockslide in northern Yosemite is one such example, consisting of 2.1 × 106 m3 ± 1.6 × 106 m3 of talus (1.5 × 106 m3 original volume of rock mass) that slid across the floor of Tiltill Valley, partially damming Tiltill Creek to create a seasonal pond that drains through and around the rockslide mass. This volume and the rockslide's effective coefficient of friction, 0.47, place it near the boundary between long-runout landslides and ordinary Coulomb failure. Although the rockslide superficially appears to consist of two separate lobes, statistically indistinguishable 10Be exposure dates from eight samples indicate a single event that occurred at 13.0 ± 0.8 ka. The age of the Tiltill rockslide and its relatively low elevation compared to equilibrium line altitudes at this place and time make glacial debutressing a highly unlikely triggering mechanism. Seismic shaking associated with fault rupture along the eastern Sierra Nevada is shown to be a plausible but unverified trigger.

scholarly journals The distribution of woody species in relation to climate and fire in Yosemite National Park, California, USA

Fire Ecology ◽  
2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Jan W. van Wagtendonk ◽  
Peggy E. Moore ◽  
Julie L. Yee ◽  
James A. Lutz
Keyword(s):  
Plant Species ◽  
Sierra Nevada ◽  
Species Distribution ◽  
National Park ◽  
Woody Plant ◽  
Fire Regime ◽  
Yosemite National Park ◽  
Distribution Models ◽  
Ecological Zones ◽  
Woody Plant Species

Abstract Background The effects of climate on plant species ranges are well appreciated, but the effects of other processes, such as fire, on plant species distribution are less well understood. We used a dataset of 561 plots 0.1 ha in size located throughout Yosemite National Park, in the Sierra Nevada of California, USA, to determine the joint effects of fire and climate on woody plant species. We analyzed the effect of climate (annual actual evapotranspiration [AET], climatic water deficit [Deficit]) and fire characteristics (occurrence [BURN] for all plots, fire return interval departure [FRID] for unburned plots, and severity of the most severe fire [dNBR]) on the distribution of woody plant species. Results Of 43 species that were present on at least two plots, 38 species occurred on five or more plots. Of those 38 species, models for the distribution of 13 species (34%) were significantly improved by including the variable for fire occurrence (BURN). Models for the distribution of 10 species (26%) were significantly improved by including FRID, and two species (5%) were improved by including dNBR. Species for which distribution models were improved by inclusion of fire variables included some of the most areally extensive woody plants. Species and ecological zones were aligned along an AET-Deficit gradient from cool and moist to hot and dry conditions. Conclusions In fire-frequent ecosystems, such as those in most of western North America, species distribution models were improved by including variables related to fire. Models for changing species distributions would also be improved by considering potential changes to the fire regime.

Quantifying the fire regime distributions for severity in Yosemite National Park, California, USA

2011 ◽  
Vol 20 (2) ◽  
pp. 223 ◽  
Author(s):  
Andrea E. Thode ◽  
Jan W. van Wagtendonk ◽  
Jay D. Miller ◽  
James F. Quinn
Keyword(s):  
Sierra Nevada ◽  
National Park ◽  
Fire Regime ◽  
Fire Severity ◽  
Fire Regimes ◽  
Montane Forest ◽  
Subalpine Forest ◽  
Yosemite National Park ◽  
Forest Zone ◽  
Frequency Distributions

This paper quantifies current fire severity distributions for 19 different fire-regime types in Yosemite National Park, California, USA. Landsat Thematic Mapper remote sensing data are used to map burn severity for 99 fires (cumulatively over 97 000 ha) that burned in Yosemite over a 20-year period. These maps are used to quantify the frequency distributions of fire severity by fire-regime type. A classification is created for the resultant distributions and they are discussed within the context of four vegetation zones: the foothill shrub and woodland zone; the lower montane forest zone; the upper montane forest zone and the subalpine forest zone. The severity distributions can form a building block from which to discuss current fire regimes across the Sierra Nevada in California. This work establishes a framework for comparing the effects of current fires on our landscapes with our notions of how fires historically burned, and how current fire severity distributions differ from our desired future conditions. As this process is refined, a new set of information will be available to researchers and land managers to help understand how fire regimes have changed from the past and how we might attempt to manage them in the future.

scholarly journals Investigation and hazard assessment of the 2003 and 2007 Staircase Falls rock falls, Yosemite National Park, California, USA

2008 ◽  
Vol 8 (3) ◽  
pp. 421-432 ◽  
Author(s):  
G. F. Wieczorek ◽  
G. M. Stock ◽  
P. Reichenbach ◽  
J. B. Snyder ◽  
J. W. Borchers ◽  
...  
Keyword(s):  
National Park ◽  
Three Dimensional ◽  
Source Area ◽  
Rock Fall ◽  
Yosemite National Park ◽  
Rock Falls ◽  
Joint Spacing ◽  
Hydrologic Processes ◽  
Yosemite Valley ◽  
Triggering Mechanisms

Abstract. Since 1857 more than 600 rock falls, rock slides, debris slides, and debris flows have been documented in Yosemite National Park, with rock falls in Yosemite Valley representing the majority of the events. On 26 December 2003, a rock fall originating from west of Glacier Point sent approximately 200 m3 of rock debris down a series of joint-controlled ledges to the floor of Yosemite Valley. The debris impacted talus near the base of Staircase Falls, producing fragments of flying rock that struck occupied cabins in Curry Village. Several years later on 9 June 2007, and again on 26 July 2007, smaller rock falls originated from the same source area. The 26 December 2003 event coincided with a severe winter storm and was likely triggered by precipitation and/or frost wedging, but the 9 June and 26 July 2007 events lack recognizable triggering mechanisms. We investigated the geologic and hydrologic factors contributing to the Staircase Falls rock falls, including bedrock lithology, weathering, joint spacing and orientations, and hydrologic processes affecting slope stability. We improved upon previous geomorphic assessment of rock-fall hazards, based on a shadow angle approach, by using STONE, a three-dimensional rock-fall simulation computer program. STONE produced simulated rock-fall runout patterns similar to the mapped extent of the 2003 and 2007 events, allowing us to simulate potential future rock falls from the Staircase Falls detachment area. Observations of recent rock falls, mapping of rock debris, and simulations of rock fall runouts beneath the Staircase Falls detachment area suggest that rock-fall hazard zones extend farther downslope than the extent previously defined by mapped surface talus deposits.

Late Wisconsin Paleoecologic Record from Swamp Lake, Yosemite National Park, California

1992 ◽  
Vol 38 (1) ◽  
pp. 91-102 ◽  
Author(s):  
Susan J. Smith ◽  
R. Scott Anderson
Keyword(s):  
Sierra Nevada ◽  
National Park ◽  
Late Glacial ◽  
Yosemite National Park ◽  
Conifer Forest ◽  
The Core ◽  
Mixed Conifer Forest ◽  
Mono Craters ◽  
Climatic Regime ◽  
Cooling Trend

AbstractA 7.86-m sediment core from Swamp Lake in Yosemite National Park, California, provides a continuous record of environmental change over the last ca. 16,000 yr, as inferred from pollen, macrofossil, and microscopic charcoal analyses. The core stratigraphy documents late Wisconsin (Tioga stage) deglaciation between >16,000 and 13,700 yr B.P., approximately 6000-3500 yr earlier than higher-elevation Sierra Nevada records. The core includes five volcanic ash layers, chemically identified as four Mono Craters ashes and the Tsoyawata ash (Mt. Mazama, Oregon). The fossil record shows that herbs and sagebrush dominated the glacial environment at Swamp Lake. By 12,000 yr B.P., a mixed conifer forest composed of high- and mid-elevation conifers grew around the lake, suggesting a cool, wet late-glacial environment. The modern Sierra montane forest did not become established until ca. 10,400 yr B.P., when maximum charcoal concentrations and minimum fir pollen percentages indicate an early Holocene xeric period. The record suggests that a cooling trend began ca. 6500 yr B.P. and persisted until ca. 3700 yr B.P. when the modern climatic regime was established.

Short-term resilience of Great Gray Owls to a megafire in California, USA

The Condor ◽  
2019 ◽  
Vol 121 (1) ◽  
Author(s):  
Rodney B Siegel ◽  
Stephanie A Eyes ◽  
Morgan W Tingley ◽  
Joanna X Wu ◽  
Sarah L Stock ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
National Park ◽  
Hierarchical Modeling ◽  
Fire Regimes ◽  
Burned Area ◽  
National Forest ◽  
Yosemite National Park ◽  
Bayesian Hierarchical ◽  
Rim Fire ◽  
Great Gray Owl

ABSTRACT Throughout western North America, longer, hotter fire seasons and dense fuels are yielding more frequent, larger, and higher-severity wildfires, including uncharacteristically large “megafires.” Wildlife species associated with late-seral forest characteristics may be particularly vulnerable to habitat loss stemming from changing fire regimes. The Great Gray Owl (Strix nebulosa) is a state-listed endangered species in California that typically nests in large snags in well-shaded forests adjacent to montane meadows. The 2013 Rim Fire burned 104,000 ha in Yosemite National Park and Stanislaus National Forest, making it the largest recorded fire in California’s Sierra Nevada. The fire perimeter contained 23 meadows known to be occupied by Great Gray Owls during the decade prior to the fire, representing nearly a quarter of all known or suspected territories in California at the time. We analyzed 13 yr (2004–2016) of Great Gray Owl detection/non-detection data from 144 meadows in the central Sierra Nevada, including meadows inside and outside the Rim Fire perimeter in Yosemite National Park and on Stanislaus National Forest. During 3 yr of surveys after the fire, Great Gray Owls were detected at 21 of 22 meadows surveyed within the fire perimeter that were occupied during the decade prior to the fire. Bayesian hierarchical modeling revealed that, rather than decreasing after the fire, persistence of owls at meadows actually increased on both National Park Service (NPS) and non-NPS lands, while colonization rates exhibited no significant change. Within the burned area, these dynamics were unrelated to forest structure variables describing post-fire stands around individual meadows. Notably, post-fire increases in owl persistence occurred both inside and outside the fire perimeter, suggesting factors other than the fire were likely favorable to Great Gray Owls during the post-fire years. Great Gray Owls appear to have been largely resilient to effects of the Rim Fire during the 3 yr after it burned.

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