GEOL107 Lecture Notes - Fall 2018 Lecture 8 - Solifluction, Slid (Fluke song), Grade (slope)
20 Sep 2018
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Document Summary
Movement of rock and/or soil downhill under influence of gravity. Mass movement events can occur at variety of velocities from as fast as 100 km/hr to as slow as mm/yr. Nature - type and orientation - of surface/near-surface materials. Rockslide in wyoming in spring of 1925. Estimated that 37 million m3 of rock and soil slid downhill at speeds approaching. 60 km/hr and settled into the valley floor. Nature (type and orientation) of surface/near-surface materials. Rock layers were inclined tilted - less stable than horizontal layers. Inclined sandstone layer (allows water to flow through it) on top of shale layer (water doesn"t flow through it) Prior to rockslide, river in valley cut through sandstone - oversteepening slope of sandstone. Water from excessive rain and snowmelt went through sandstone and collected on top of shale. This water acts as lubricant between sandstone and shale. Small earthquake in nearby grand teton mtns. caused unstable sandstone layer to break loose and slide downhill.
