Sapping

Sapping is a type of erosion where the ground seems to have collapsed into wide valleys. Steep-sided U-shaped valleys of fairly uniform width with box-like, "theater-shaped" headwalls are characteristic of sapping. ^[1] Sapping is caused by water in the ground moving laterally until it eventually seeps out and creates its ampitheater-like shape. Valleys made by sapping occur throughout the world including in England, Colorado, Hawai’i, New Zealand, and other places. ^[2]

The two canyons at center-left in this photo from Canyonlands National Park in Utah have the theater-shaped heads typical of valley features shaped by groundwater sapping.

Probable valleys made by sapping Close-up of Nirgal Vallis, as seen by themis. Location is 27.6 S and 315.2 E. Image is 18.3 km wide.

Many channels have been seen on Mars that look like ones created by groundwater sapping here on Earth.^[3] ^[4]

References

↑ Kocher, R. and J. Piper. 1986. Morphology of Large Valleys on Hawaii: Evidence for Groundwater Sapping and Comparisons with Martian Valleys. Journal of Geophysical Research. volume = 91. Issue = B13|pages = 175–192.
↑ Nash, D. 1996. GROUNDWATER SAPPING AND VALLEY DEVELOPMENT IN THE HACKNESS HILLS, NORTH YORKSHIRE, ENGLAND. Earth Surface Processes and LandformsVolume 21, Issue 9 p. 781-795
↑ Gulick, V. 2001. Origin of the Valley Networks on Mars: a Hydrological Perspective. Geomorphology. volume = 37. issue = 3–4. 41–268
↑ Sharp, R. P., & Malin, M. C. 1975. Channels on Mars. Geological Society of America Bulletin. 86(5). 593–609.