GEO 330 Lecture Notes - Lecture 16: Mcmurdo Dry Valleys, Fretted Terrain, Arsia Mons
30 Mar 2018
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Document Summary
Most valleys in fretted terrain have flat floors with distinct lineations. Lineations composed of closely packed pits and mounds a few tens of meters across. Lineations likely caused by convergence of debris aprons from opposing valley walls. Valleys in the 30-60 latitude belts tend to be wider than those at lower latitudes, and they also tend to widen downstream. Valley formation probably started with dissection of fretted terrain in the noachian, just as for other valley networks. Valleys were then modified by debris flow processes. Elevation drops across the plains-highlands boundary, so valleys were deeper closer to the boundary. After main valley-forming period was over, valleys widened due to viscous flow of material away from valley walls. Valleys widen downstream because original valleys were deeper downstream and could hold more fill. Strongest case for glaciers can be made for flanks of each of the tharsis volcanoes and olympus.
