Periodically Spaced Channels in Geomorphology

Saturday, September 29, 2001 - 11:00am - 12:00pm
Keller 3-180
Norbert Schorghofer (Massachusetts Institute of Technology)
Joint work with Arshad Kudrolli and Daniel H. Rothman.

Periodically spaced fluvial channels are observed in various geomorphic settings, such as mountain belts, fault blocks, submarine canyons, and Martian gullies. We study this phenomenon in porous sand using field observations, sapping experiments, numerical simulations, and analytical theory. In field observations we observe channels initiated by surface phenomena, but growing due to water provided from underground. The periodicity is established in the initial stage of channel formation. Periodic channels are also reproduced in a tabletop experiment with a dozen and more parallel channels observed. As a result of these observations, the problem is formulated in terms of flow in a porous medium with moving interfaces. Small deformations of the underground watertable provide an efficient instability mechanism. The length-scale of the spacing between channels is discussed.