Nature and origin of stone stripes on the Columbia Plateau |
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| Authors: | George W Cox Jodee Hunt |
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| Institution: | (1) Department of Biology, San Diego State University, 92187-0057 San Diego, CA, USA;(2) Present address: Arkansas Cooperative Fish and Wildlife Research Unit, U.S. Fish and Wildlife Service, Department of Zoology, University of Arkansas, 72701 Fayetteville, AR, USA;(3) Department of Biology, San Diego State University, 92182 San Diego, CA, USA |
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| Abstract: | Beds of size-sorted stones forming stripes perpendicular to the contour are conspicuous on hillsides of the Columbia Plateau. Stripes occur on terrain ranging from 0° to about 30° in steepness, often beginning among Mima-type mounds on mesa tops and extending downward onto steep, unmounded slopes. Four mechanisms of their origin have been hypothesized: 1) water erosion, 2) solifluction and soil creep, 3) weathering of rock outcrops, and 4) tunneling by pocket gophers. We measured characteristics of five stripes on slopes of differing exposure and steepness. These stripes were 58–124 m long, and widths showed a maximum range of 0.55–3.70 m. Data on physical and biotic characteristics of the stripes suggest that pocket gopher tunneling is a basic mechanism of stripe formation on gentle slopes, and that this mechanism is augmented by outcrop weathering and colluvial dynamics on steeper slopes, with erosion playing a secondary role. |
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| Keywords: | basalt weathering Columbia Plateau erosion fossorial rodents Mima mounds stone stripes Thomomys talpoides |
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