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<br />i)J~'~3S <br /> <br />Chopler 3 - Affect";' Enviroltl7lC1ll <br /> <br />l'iibhr3~1;i:t(V>A:"'~.:Ailiiiiiindi!SlUArellGeoI6MCHI6.aNIii;...., <br /> <br />:H>Y~/\:::-t:\::</%r?%,j:: <br /> <br />rock slides Area rock slides arc mostly dip-slope and wedge 138,5 20.4 <br />faihues in lbe Maroon and State Bridge Formations; <br />l1X)st slide blocks have moved less than 300 feet <br />downslope; also includes mixed lill and rock slides nf <br />various sizes on the steep valley sldewalls of lower <br />Maroon Creek; lbese slides detacbed and reacbed lbe <br />valli:y floor. <br /> <br />debris Thin slab failures of glaciallill or coUuviwn overlying <br />slides bedrock; usually triggered by rapid precipitation or <br />snowmell: found at the heads of first-order drainages <br />am on steep unvegctated slopes, such as at lower <br />Maroon Creek, <br /> <br />Surface soil erosion and riDing 00 steep slopes wbere <br />the narural forest vegetation has been rerooved. <br /> <br />Includes dip slopes adjacenlto or similar to locations <br />of past rock slides and wedge failures. <br /> <br />IlazanlJSymbol <br /> <br />Unstable <br />slopes <br /> <br />erosion! <br />riDing <br /> <br />Potentially <br />unstable <br />slopes <br /> <br />rock slides <br /> <br />debris <br />slidcs/ <br />accelerate <br />d creep <br /> <br />Dcbris.l1ow and debris- <br />avalanche-prone slopes <br /> <br />Rockfail <br /> <br />Gravitational spreading <br />(Sackung) <br /> <br />Soil and talus creep <br /> <br />Totals <br /> <br />Description <br /> <br />Includes steep s10pes with a lhin mantle of coUuviwn <br />or tilL especially those areas adjacent to past debris <br />slides, m:1 areas above debris fan aJXl alluvial fan <br />deposits; lbe mapped estcnl of potential debris slide <br />areas probably WlderestimaleS its true extent. <br /> <br />Slopes wbere debris flows and debris avalancbes <br />deposit lbeir scdimcnl; typically lbe surfaces of <br />ailuvial fans of debris fans. found allbe base of steep <br />glacial valli:y sidewalls. <br /> <br />Includes rockfail source areas (cliffs) and <br />active/inactive talus deposits below lhe cliffs. <br /> <br />Slow, deep-seated borizontal spreading of steep <br />mountain ridges due to gravity; results in topograpbic <br />features sucb as upslope- and downslope-facing <br />sclU]ls, double-crested ridges, and closed depressions; <br />found along lbe ridge crest between Cloud Nine and <br />HigbJand Peak. <br /> <br />The slow. namraI downslope movemeDl of regolith <br />due to freeze-thaw and shrink-swell processes; <br />occasiooally results in pistol-butted trees and tilted <br />fe~ posts. <br /> <br />Maroon Creek <br />acres % <br /> <br />Castle Creek <br />acres % <br /> <br />Dislribution <br /> <br />18.9 <br /> <br />7.4 Maroon Bow~ <br />slopes of Castle <br />Creek <br /> <br />0.0 0.0 0,4 0.2 Heads of Ist- <br /> order drainages, <br /> Castle Creek <br />t5,6 2.3 0,0 0.0 Steep ski runs <br />97.1 14.3 40.9 16.1 Maroon Bow~ <br /> below Moment 0 <br /> Trulh CI1Wallt <br />[included wilb rock slides] Heads of first- <br /> order drainages <br /> <br />301.7 44.5 t71.0 67.5 Basins fronted by <br /> alluvial/debris <br /> fam <br />124,6 18.4 12.7 5.0 Maroon Creek <br /> side of ridge, <br /> higb elevation <br />[dispersed linear features] Ridge crest <br /> between Cloud 9 <br /> and HigbJand <br /> Peak <br />0.0 0.0 9.2 3.6 Isolated talus and <br /> rock glaciers, <br /> Maroon Creek <br />677,6 100 253.2 100.0 <br /> <br />minor slumping near its confluence with Robinson's Run. In addition, the 1994 excavation of a 20-foot-deep <br />pit at midway undermined the toe of the ski slope to the south, initiating a shallow slab slide before the pit was <br />backfilled. The first two of these incidei1ts are described briefly below, while all are described in detail in the <br />Geology, Geologic Hazards, and Soil Hazards Technical Report (Geo-Haz 1996). <br /> <br />Slides Near the Moment of Truth Catwalk <br />A 30-foot-wide section of the Momeot of Truth Catwalk, roughly 1,285 feet southwest of the old Grand Prix <br />lower terminal, was completely removed on June 15, 1995. This section of the catwalk is lI'aversed by surface <br />drainage diverted from ski runs approximately 350 feet higher on the slope. Snowmelt runoff led to erosion of <br />the inslope gully several yards inslope, 2 feet deep, and 15 feet wide (2 to 3 times its 1993 width), which <br /> <br />Geology and Soils <br />G~ologjc Hazards <br /> <br />3-5 <br />