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Activities > Surficial Geology & Soil Texture Modeling

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[ || Soil Moisture || Geology & Soil Texture || Biological Soil Crusts || Fire || Vegetation Dynamics || Soil Compaction || Wind Erosion || Climate || Repeat Photography || Land Use History || Spatial Modeling || ]

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Alluvial fan extending from the Panamint Mountains to the floor of Death Valley. Note the different colors, which correspond to different degrees of soil development and are closely related to the age of the deposits. Photograph by David Miller, USGS.

Understanding desert landscape requires knowledge of the integrated web of biotic and abiotic processes acting at and near the surface. Conversely, a well-characterized landscape carries much information on desert processes. This activity develops geographic information system (GIS) databases of surficial geology to characterize the landscape using a combination of remote sensing and detailed field work. These databases are then used to model vulnerability to and recoverability from to a variety of disturbances.

Geomorphic characteristics, including particle size distributions and soil development, were mapped in great detail at two study sites in the northern Mojave: Greenwater Valley and Valjean Valley. This information, which serves as a basis for interdisciplinary study, is extended at a regional scale (1:100,000) by geologic mapping to extrapolate the spatial models of recoverability and vulnerability.

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Methodology

Geologic mapping was accomplished by standard field methods including describing the geomorphology and the pedogenic soil development. Field studies are tied to interpretation of high-resolution aerial photographs and other remote sensing products such as Landsat 7 images. Other field data collected are intended to tie the geology to related datasets, including vegetation cover and species, biological soil crust cover, soil texture, mammal burrow density, and microtopography.

By using simple geologic process models, textural data from laboratory particle size determinations can be mapped across the landscape. Textural data can help predict biological soil crust occurrence and soil moisture. The fundamental tool for the texture model is the surficial geologic map, which describes process-specific deposits and pedogenic soil development, each of which influences texture in predictable ways.

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Highlights and Key Findings

Along with the companion geologic mapping project on surficial geology and processes in the southwest, four 1:100,000-scale quadrangles were mapped in the eastern Mojave Desert. Major sections of three additional maps were completed. These form the base data for modeling many other ecological attributes of the desert.

A study of an off-highway vehicle area was completed for the Bureau of Land Management, and the results were presented at a Monitoring Workshop and a Desert Symposium.

Analyses of texture data are underway in laboratories, and the resulting data will be used to construct texture maps of the area.

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Products

Miller D.M., and Yount, J.C., 1999, Surficial geology and geomorphic process studies in support of multidisciplinary ecosystem investigations: Examples from parts of Greenwater and Valjean Valleys, Mojave Desert ecosystem in Slate, J., ed., Proceedings of Conference on Status of Geologic Research and Mapping, Death Valley National Park: U.S. Geological Survey Open-File Report 99-0153, p.113-114.

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