Mathematics – Logic
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p34a..07l&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P34A-07
Mathematics
Logic
1625 Geomorphology And Weathering (0790, 1824, 1825, 1826, 1886), 1825 Geomorphology: Fluvial (1625), 5415 Erosion And Weathering
Scientific paper
Networks of valleys with amphitheater-shaped headwalls are prominent features on the surface of Mars. These landforms are commonly used as diagnostic indicators of undermining and headwall retreat by groundwater-seepage erosion. Of perhaps any canyon ever studied, Box Canyon, Idaho, most strongly meets the proposed morphologic criteria for groundwater sapping because it is incised into a basaltic plain with no drainage network development upstream, and approximately 10 m3/s of seepage emanates from its vertical headwall. However, we have found strong evidence that this canyon was carved during large-scale flooding about 45,000 years ago. Such evidence includes 4He and 14C dates, plunge pools, large boulders, and scoured rock along the rim of the canyon headwall. To explain the formation of the amphitheater headwall of Box Canyon, we propose that near vertical knickpoints can persist during retreat due to waterfall- induced toppling in fractured rock (e.g., columnar basalt). At a waterfall, rock columns are affected by shear and drag from the overflowing water, buoyancy from the plunge pool at the foot of the waterfall, and gravity. A torque balance is used to determine the stability of a rock column and any individual blocks that compose the column. Model results and flume experiments indicate that rotational toppling failure should occur about the base of a headwall (and therefore preserve its form during upstream propagation) where columns are tilted in the downstream direction, or slightly tilted in the upstream direction depending on the plunge pool height. We propose that such conditions are probably common in columnar-basalt bedrock. Thus, our toppling model might explain the origin of steep amphitheater headwalls in volcanic terrains on Earth and Mars by overflowing water and in the absence of seepage.
Dietrich William E.
Lamb Michael P.
No associations
LandOfFree
Waterfall erosion, rock toppling, and the formation of amphitheater-headed canyons in fractured rock does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Waterfall erosion, rock toppling, and the formation of amphitheater-headed canyons in fractured rock, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Waterfall erosion, rock toppling, and the formation of amphitheater-headed canyons in fractured rock will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1238095