| 102nd Annual Meeting of the Cordilleran Section, GSA, 81st Annual Meeting of the Pacific Section, AAPG, and the Western Regional Meeting of the Alaska Section, SPE (8–10 May 2006) | |
| Paper No. 30-6 | |
| Presentation Time: 10:20 AM-10:40 AM | ||
U-SHAPED GLACIAL VALLEYS, A MYTH? | ||
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PALMES, John, Univ of Alaska, Box 20454, Juneau, AK 99802-0454, johnpalmes@gci.net It is classic geomorphic “wisdom” (Playfair,1802) that bedrock is eroded by streams to, form “fluvial” valleys with V-shaped cross sections. Fluvial valleys, when occupied by glaciers, are then eroded into “U-shaped” valleys. Graf (1970) found the glacial valley cross section is not really U-shaped, but parabolic, with concave slopes of the form y = axb. However, this study of cross sections of recently glaciated valleys near Juneau, Alaska found only 25% of cross sections had one uniformly concave side and only .03% were concave on both sides of the valley. Of 138 slopes, only 12% were concave, while 51% were convex, and 39% of all slopes were straight. It appears that cross sectional shape is not a reliable way to determine if a valley has been glaciated. 33% of valley cross sections had one side less than 2/3 as high as the opposite. This indicates that glacial flows in these valleys were most likely constrained and directed by adjacent glaciers rather than by the bedrock. | ||
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102nd Annual Meeting of the Cordilleran Section, GSA, 81st Annual Meeting of the Pacific Section, AAPG, and the Western Regional Meeting of the Alaska Section, SPE (8–10 May 2006)
General Information for this Meeting | ||
| Session No. 30 GSA: Glaciers, Climate, and Landforms Anchorage Hilton Hotel: Fireweed 8:20 AM-11:00 AM, Wednesday, 10 May 2006 Geological Society of America Abstracts with Programs, Vol. 38, No. 5, p. 77 | ||
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