LEGIONS OF LOBES: SELF-ORGANIZATION AND MOVEMENT OF SOLIFLUCTION FEATURES AT NIWOT RIDGE

Solifluction, the downslope flow of sediment on alpine hillslopes due to freeze-thaw processes, commonly produces distinctive patterns of terraces and lobes. We study numerous examples of these features on Niwot Ridge in the Colorado Front Range. First, we examine the organization of solifluction terraces and lobes at Niwot Ridge, using 1-meter aerial LiDAR to map them in detail. Terraces are elongate along contour, several m in amplitude, and 60-100 m in wavelength. In places the terraces break into rocky lobes several meters in width along contour and may be very elongated. We explore potential physical explanations of the observed patterns of lobes and terraces by drawing direct comparison with instabilities of viscous fluids on inclined planes described in fluid mechanics literature. We find that interplay between gravitational forces and cohesion of the soil can produce the observed patterns. Finally, we present preliminary field measurements of the rates of surface motion of two solifluction lobes during the summer of 2017. We compare these rates with measurements collected by James Benedict from 1964-1967 on the same lobes, linking our findings with long-term climate data from the nearby Long Term Ecological Research site.