Bedrock erosion in the lower Big Wood River channel, southcentral Idaho

Conference · Thu Apr 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5098513

Maley, T S; Oberlindacher, P ^[1]

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1. Bureau of Land Management, Boise, ID (United States)

The Big Wood River, which is fed from the mountains to the north of the Snake River Plain, cuts through 0.8 m.y. old basalt in an area north and east of Shoshone, Idaho. The basalt channel carved by the Big Wood River exhibits remarkable and unusual bedrock erosional features. Approximately 10,000 years ago, nearby Black Butte shield volcano erupted basaltic lave which rerouted the Big Wood River. At the time the new river channel formed 10,000 years ago, alpine glaciers in the mountains were also beginning to melt. High flows of water from the melting glaciers during the next few thousand years carried large sediment loads and were instrumental in developing the spectacular potholes now found in the channel. Most of the scouring agents are pebbles and cobbles derived from quartzite, granitic, and gneissic rocks. As potholes began to develop, they were closely spaced and generally less than 1 m apart. However, as the potholes enlarged and expanded both horizontally and vertically, they coalesced with one another. The merging process occurred when the walls of two or more adjacent potholes were breached by the outward expansion of each pothole. The deeper of the two potholes captured the pebbles of the adjacent pothole. When pebbles are captured, pothole growth is terminated and the more shallow pothole was gradually cannibalized. All of the features within the channel are overprinted with a strong asymmetry caused by the current-driven pebbles against the upstream side of the features. Consequently, the upstream side of the features tends to be smooth, convex and rounded; whereas, the downstream side tends to be concave with the leading edge of the feature pointing in the downstream direction.

• OSTI ID: 5098513
• Report Number(s): CONF-9305259-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
BASALT
EROSION
GEOLOGIC FORMATIONS
IDAHO
ABRASION
ALLUVIAL DEPOSITS
DRAINAGE
GEOLOGIC STRUCTURES
GEOMORPHOLOGY
HYDROLOGY
RIVERS
SEDIMENTS
SNAKE RIVER PLAIN
VALLEYS
WATER CURRENTS
CURRENTS
DEVELOPED COUNTRIES
GEOLOGIC DEPOSITS
GEOLOGY
IGNEOUS ROCKS
NORTH AMERICA
ROCKS
STREAMS
SURFACE WATERS
USA
VOLCANIC ROCKS
580000* - Geosciences