GEOL 102 Lecture Notes - Lecture 20: Desert Varnish, Valley, Debris Flow
15 Mar 2018
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Thursday, week 10, lecture #18 , class #20. Iclicker: after ice melts, what would you expect to see at x. Hanging valley, steep cliff side where they intersect, water drainage in the valley. Iclicker: ice glowed from smooth surface (abrasion) and moves towards x (steeper cliff base) with plucking. Iclicker: oldest to youngest desert varnish debris flow deposits: Oldest= darkest sediment youngest = lightest. No permanent surface water and no more than 15% vegetation cover. Key feature: dry air mass moves over landscape, wicks away any moisture that is on that landscape. Coastal (cold ocean temp= no evap= dry air) Weathering, soil formation, erosion by water and wind, sediment deposition. Mechanical weathering (primary form of weathering because there is little moisture for chemical) Get darker as they go through oxidation. Water (deserts have little water, yes, but some short periods of intense precipitation) Fast sediment erosion due to flash floods. Water promoting physical weathering and sediment transport.
