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Neotectonics of the northern Mojave Desert

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Geologic modeling: Fundamental to geologic mapping is the need to understand how the landscape is changing over time, and how surface exposure of earth materials affects soil development and erosion rates over time. The diagram below illustrates important knowledge gained from careful observations and testing scientific hypotheses to create a model of how weathering, erosion, and deposition processes, over time, influence the development of the landscape. Models like this are essential to classifying the landscape into mapable units that can be used in conjunction with aerial photography and other types of imagery to create geologic maps. These models are linked to knowledge gained about changing climate conditions during glacial and interglacial periods of the Quaternary Period, and during the more recent Holocene Epoch when human populations advanced into the Mojave Desert region. Models like this are essential to understand the processes changing the landscape, climate cycles (warm, cold, wet, or dry), and provide insight into how plant communities develop and respond to climate change and other human-induced changes to the landscape.

Terrace age diagram showing the geomorphic and soil profile features that develop and change over time

The diagram shows an idealized profile of near earth surface materials in a cross-section profile perpendicular to an idealized stream valley on an alluvial fan in the Mojave Desert region. The diagram shows the relationship of seven major stream incision and channel back-filling cycles and the associated formation of stream terrace and associated soil profiles that formed on them over time. Note that not all streams display evidence of seven cycles everywhere because stream channels change and migrate over time, become abandoned or inactive, or are influenced by tectonic changes and other forces that modify the landscape over time. However, also note that different terrace levels that are preserved on the landscape typically have unique and recognizable soil profiles that can be used for geologic mapping. These different kind of soils play an important role in how water infiltrates into the ground and the kind of plants that those soils can support.
graphic provided by David Miller

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