Surface and subsurface dynamics of a perennial slow-moving landslide from ground, air and space

Landslides modify the natural landscape and cause 11 fatalities and property damage12 worldwide. Quantifying landslide dynamics is challenging due to the stochastic nature of the13 environment. With its large area of ~1 km2 and perennial motions at ~10-20 mm per day, the14 Slumgullion landslide in Colorado, USA, represents an ideal natural laboratory to better15 understand landslide behavior. Here, we use hybrid remote sensing data and methods to16 recover the four-dimensional surface motions during 2011-2018. We refine the boundaries17 of an area of ~0.35 km2 below the crest of the prehistoric landslide. We construct a18 mechanical framework to quantify the rheology, subsurface channel geometry, mass flow19 rate, and spatiotemporally dependent pore-water pressure feedback through a joint analysis20 of displacement and hydrometeorological measurements from ground, air and space. Our21 study demonstrates the importance of remotely characterizing often inaccessible, dangerous22 slopes to better understand landslide mechanisms, landscape modification, and other quasi23static mass fluxes in natural and industrial environments, which will ultimately help reduce24 landslide hazards.