Title: The Owens River as a Tiltmeter for Long Valley Caldera, California
Abstract: In the lower 11 km of its course around the resurgent dome of Long Valley caldera, the Owens River displays two parallel meander belts, comparable in meander wavelength and amplitude but unequal in age, elevation, and discharge. It appears the two belts take turns carrying the river's flow depending on whether the dome is inflating or subsiding. The inboard belt, some 200-300 m closer to the dome and now 30-60 cm higher in elevation, contains an underfit stream and is now being abandoned. The outboard channel formed in a series of avulsions apparently induced by recent uplift of the dome. In the upper 4 km of the two-channel reach, avulsion occurred between 1856 and 1878 as inferred from the original U.S. Coast and Geodetic Survey mapping in the caldera. Avulsion had already occurred by 1856 in the lower 4 km of the river, suggesting a possible migration of the center of uplift through time. Muted remains of older oxbows in the outboard meander belt indicate an earlier occupancy by the river, and thus an earlier episode of uplift, separated from the current uplift by an era of subsidence. More ancient meander scars at the inboard and outboard limits of the floodplain imply additional earlier episodes of inflation and subsidence. Projection of surveyed topographic profiles across the river's floodplain to the center of the dome suggests that cumulative recent uplift is on the order of 15-35 m, or about 30-70 times greater than that measured for the caldera since 1979 (Castle et al. 1984). The duration of the era of subsidence can be estimated by comparing oxbow densities in the old and new meander belts in the upper two-channel reach; the data suggest that the dome may have been in subsidence for a period of at least 500 to 1000 yr ending about 150 yr ago. No eruptions of the Long Valley volcanic system have accompanied these inflations and subsidings. However, the 14th century eruptive activity of the Inyo Craters volcanic chain may have coincided in time with the subsidence implied by the river's occupancy of the inboard meander belt.
Publication Year: 1992
Publication Date: 1992-05-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 55
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