Landslides are one of the most spectacular mass wasting features on Mars in terms of their areal extent and volume. Some of the best preserved landslides are in the Valles Marineris canyon system, but that's not the only place we see evidence for landslides.
This image of Bahram Vallis, a valley along the edges of the circum-Chyrse Basin, has large mounds of material at the base of the valley floor. These deposits of material are different from those deposits seen at Valles Marineris. They do not have a "ribbed" surface of transverse ridges. They also do not have a semi-circular distal margin giving it a lobate appearance and they have not traveled for many kilometers away from their source region like most Valles Marineris landslides do.
These particular deposits have the characteristic shape of rotational landslides or slumps on Earth where material along the entire wall slumps down and piles debris at the base of the slope, much like a person who slumps down the back of a chair. Right at the cliff edge at the top of the slope, the shape of the area where the valley wall gave way to a landslide is not straight, but rather curved or semi-circular. This is typical of large landslides where the failure area has an arcuate "crown" shape. The fact that landslides have occurred here indicates that the valley walls are not stable and the materials respond to Martian gravity with mass movements.
Scientists studying landslides can use these images along with topographic data to model how the wall failed, which can give clues to the nature of the materials (type, strength, etc.) in this region. Another consequence of landslide activity in Bahram Vallis is that the overall width of the valley will increase over time.
Photo credit: NASA/JPL/University of Arizona
No comments:
Post a Comment