On May 25, 2014, a 54.5-million cubic meter rock avalanche in the West Salt Creek valley, Mesa County, Colorado, traveled 4.6 kilometers, leaving a deposit that covers about 2.2 square kilometers. To check the particle-size distribution of the deposit for information about the high mobility of the avalanche, we estimated boulder distribution density for the entire deposit by counting 1-meter (m) or larger diameter boulders of sedimentary rock derived from the Green River Formation that are visible in high-resolution imagery collected from the area in July 2014. Basalt boulders were excluded from the count because field observations indicated that they generally stayed intact as the avalanche moved downslope, whereas sedimentary boulders showed evidence of fragmentation during downslope movement. Variable clarity, contrast, and resolution of the imagery precluded mapping smaller boulders. Experimentation with 5-, 10-, and 20-m resolution grids indicated that a 20-m resolution grid showed the spatial pattern of boulder density across the deposit at a scale that allowed statistically meaningful variations to be determined. In addition to counting the boulders in each 20×20-m grid cell, six categories of successively increasing boulder distribution density were created to help visualize variations in the distribution of 1 meter or larger boulders across the avalanche deposit. Analysis indicates that boulder distribution density gradually decreases with increasing distance from the avalanche source.
Citation Information
| Publication Year | 2023 |
|---|---|
| Title | Distribution of large boulders on the deposit of the West Salt Creek rock avalanche, western Colorado |
| DOI | 10.3133/dr1178 |
| Authors | Adrian C. Lewis, Rex L. Baum, Jeffrey A. Coe |
| Publication Type | Report |
| Publication Subtype | USGS Numbered Series |
| Series Title | Data Report |
| Series Number | 1178 |
| Index ID | dr1178 |
| Record Source | USGS Publications Warehouse |
| USGS Organization | Geologic Hazards Science Center |
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Distribution of large boulders on the deposit of the West Salt Creek rock avalanche, western Colorado
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Distribution of large boulders on the deposit of the West Salt Creek rock avalanche, western Colorado
On May 25th, 2014, a 54.5 Mm3 rock avalanche occurred in the West Salt Creek valley in western Colorado following heavy rainfall on top of snow (Coe and others, 2016a). The data in this project includes boulder density in 20-m x 20-m grid cells for the entire West Salt Creek rock avalanche deposit. The grid cells cover 2,154,800 m2, which accounts for nearly the entire surface of the deposit. We e - Connect