Rock Glaciers of the Beartooth and Northern Absaroka Ranges, Montana, USA Zachary M

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9-2019 Rock glaciers of the Beartooth and northern Absaroka ranges, Montana, USA Zachary M. Seligman University of Montana, Missoula

Anna E. Klene University of Montana - Missoula

Frederick E. Nelson Michigan State University

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Recommended Citation Seligman, ZM, Klene, AE, Nelson, FE. Rock glaciers of the Beartooth and northern Absaroka ranges, Montana, USA. Permafrost and Periglac Process. 2019; 1– 11. https://doi.org/10.1002/ppp.2019

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Rock glaciers of the Beartooth and northern Absaroka ranges, Montana, USA

Journal: Permafrost and Periglacial Processes

Manuscript ID PPP-19-0010.R1 Wiley - Manuscript type:ForSpecial Peer Issue Paper Review Date Submitted by the 14-Jun-2019 Author:

Complete List of Authors: Nelson, Frederick; Michigan State University, Department of Geography, Environment, and Spatial Sciences; Northern Michigan University, Department of Earth, Environmental, and Geographical Sciences Klene, Anna; University of Montana, Department of Geography Seligman, Zachary; University of Montana, Geography

mapping, Montana, periglacial, rock glacier, Rocky Mountains, climate Keywords: change

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1 2 3 1 4 5 6 2 7 8 3 9 4 10 11 5 12 13 6 Rock glaciers of the Beartooth and northern Absaroka ranges, Montana, USA 14 15 7 16 8 17 18 9 19 10 For Peer Review 20 11 21 12 22 23 13 24 14 1 1 2,3 25 15 Zachary M. Seligman, Anna E. Klene, and Frederick E. Nelson 26 16 27 17 1Department of Geography, University of Montana, Missoula MT 59812, USA 28 29 18 30 19 2Department of Geography, Environment, and Spatial Sciences, Michigan State University, East 31 20 Lansing MI 48824, USA 32 21 33 3 34 22 Department of Earth, Environmental, and Geographical Sciences, Northern Michigan 35 23 University, Marquette MI 49855, USA 36 24 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 2 of 42

1 2 3 25 4 5 26 6 27 Abstract 7 8 28 Six-hundred and sixty rock glaciers in the northern Absaroka and Beartooth Ranges of south- 9 10 29 central Montana were digitized and evaluated using geographic information systems 11 12 13 30 technology and an array of topographic and environmental parameters. Beartooth rock glaciers 14 15 31 are larger, occur at higher elevations, receive more precipitation, and are subject to colder 16 17 18 32 temperatures than northern Absaroka rock glaciers. Elevation is strongly correlated with rock 19 For Peer Review 20 33 glacier activity. Comparative analysis of these adjacent mountain ranges indicates that 21 22 23 34 Beartooth geomorphic landscapes are shifting from predominantly glacial to periglacial 24 25 35 regimes, and that the northern Absarokas have largely completed this transition. Because 26 27 36 glaciers are declining in response to climatic warming, rock glaciers could soon become the 28 29 30 37 most important source of ice in the region. 31 32 38 33 34 35 39 KEYWORDS 36 37 40 climate change, ground ice, mapping, Montana, periglacial, rock glacier, northern Absaroka 38 39 41 Range, Beartooth Range, Rocky Mountains, water resources 40 41 42 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 2 60 http://mc.manuscriptcentral.com/ppp Page 3 of 42 Permafrost and Periglacial Processes

1 2 3 43 4 5 44 1. INTRODUCTION 6 7 45 As global warming proceeds, water resources derived from glaciers and mountain snowpacks 8 9 46 are increasingly threatened. Although rock glaciers have been studied for more than a century,1 10 11 12 47 looming water deficits in many arid and semi-arid mountainous regions have intensified 13 14 48 interest in these features. Because most rock glaciers are well insulated by a veneer of earth 15 16 17 49 materials, the substantial ice volumes contained in them are being considered as alternative, 18 19 50 longer-term sources of water.For2 Accompanying Peer Reviewthis increased interest is a burgeoning scientific 20 21 22 51 literature concerned with rock glaciers, including a large number of regional inventories (e.g. 23 24 52 3,4,5,6,7,8,9. Further evidence of the increasing scientific and societal importance of rock glaciers is 25 26 53 27 the International Permafrost Association’s recently established “Action Group on Rock Glacier 28 29 54 Inventories and Kinematics”.10 30 31 55 Basic mapping of periglacial landforms in the Middle and Northern Rocky Mountain 32 33 34 56 physiographic provinces (pp. 365-404)11 has not been carried out extensively, despite the 35 36 57 widespread occurrence of periglacial features and recent technological advances that make 37 38 39 58 such undertakings feasible. Although several localized rock-glacier studies have been conducted 40 41 59 in parts of the U.S. states of Montana12,13 and Wyoming,14,15,16 there have been very few 42 43 17 44 60 exhaustive inventories over extensive areas of this region. Johnson et al. produced an 45 46 61 inventory in the Lemhi Range in the adjacent state of Idaho, Legg18 worked in Glacier National 47 48 62 19 49 Park in Montana, and Florentine documented a series of rock glaciers in southwest Montana 50 51 63 that partially overlaps Seligman’s20 earlier study, albeit using highly divergent methods of data 52 53 64 collection (cf. Section 3.1 below and Florentine (pp. 11-12)19. 54 55 56 57 58 59 3 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 4 of 42

1 2 3 65 This paper represents the first such survey conducted in the northern Absaroka and 4 5 6 66 Beartooth Ranges of Montana. Here, we summarize the differences between rock glaciers in 7 8 67 the two ranges with respect to several topographic and environmental parameters based upon 9 10 20 11 68 a survey by Seligman, report similarities and differences in these parameters between the two 12 13 69 ranges, and explore how the results can be interpreted in the context of Quaternary and 14 15 16 70 contemporary climatic changes. 17 18 71 19 For Peer Review 20 21 72 2. STUDY AREA 22 23 73 The Absaroka and Beartooth ranges span the border between the U.S. states of 24 25 74 Montana and Wyoming (Figure 1), near Yellowstone National Park. These adjacent mountain 26 27 75 ranges are among the highest in the region, and prominently display the effects of both glacial 28 29 30 76 and periglacial processes. The Beartooth and northern Absaroka ranges are, respectively, the 31 32 77 first and fourth highest mountain ranges in Montana. 33 34 35 78 36 37 79 [Figure 1 near here] 38 39 40 80 41 42 81 The Absaroka Mountains form part of the Absaroka-Gallatin volcanic field, the largest 43 44 45 82 such field in the Middle and Northern Rocky Mountains. Volcanism in this region occurred along 46 47 83 two subparallel, northwest trending belts defined by hypabyssal plutons that extend for roughly 48 49 84 150 km.21 Topography developed in the Absarokas consists of the remnants of a highly 50 51 52 85 dissected plateau displaying the rugged, sculpted results of extensive glaciation, including 53 54 86 cirques, horn peaks, arêtes, U-shaped valleys, and prominent moraines. In this study we focus 55 56 57 58 59 4 60 http://mc.manuscriptcentral.com/ppp Page 5 of 42 Permafrost and Periglacial Processes

1 2 3 87 on the “Northern Absaroka Range” (hereafter “northern Absarokas”), which lies almost entirely 4 5 22 6 88 within the state of Montana. Of the many peaks rising above 3000 m.a.s.l. in the northern 7 8 89 Absarokas, Tumble Mountain (3449 m) is the tallest; at least 10 peaks in the range exceed 9 10 11 90 3300 m. Rock glaciers are the most prominent periglacial landforms in the northern Absarokas. 12 13 91 One feature at Galena Creek, south of the present study area, has played a prominent role in 14 15 14-16, 23 16 92 the history of rock-glacier research. 17 18 93 The Beartooth Mountains are dominated by metamorphosed Precambrian granite 19 For Peer Review 20 94 uplifted roughly 50 million years ago.24 Granite Peak, at 3904 m.a.s.l., forms the highest 21 22 23 95 topographic point in Montana, and several other peaks exceed 3800 m. Glaciated terrain on the 24 25 96 northeast side of the Beartooths consists of deeply eroded glacial valleys (Figure 2A). Moraines 26 27 28 97 occur in all valleys above 2750 m.a.s.l. In some major valleys they extend to below 1500 m and 29 30 98 are considered to be of early to late Pinedale (Late Pleistocene) age. Younger moraines of Late 31 32 33 99 Holocene age occur at the foot of existing glaciers and in cirques that were deglaciated recently 34 35 100 (pp. F38).25 Cirque glaciers, remnants of multiple Pleistocene glacial advances,26 occur at higher 36 37 101 38 elevations in the heads of the prominent U-shaped valleys. Ice-rich rock glaciers and talus 39 40 102 accumulations are the principal currently active periglacial features within many of these 41 42 103 valleys. 43 44 45 104 Discontinuous, high-elevation plateau-like surfaces are widespread in the Beartooths, 46 47 105 separated by the large glacial troughs (pp. 381).11 Except in the southwest part of the range, 48 49 50 106 most of these tracts remained unglaciated throughout the Quaternary and are festooned with 51 52 107 periglacial features, including tors, blockfields, large-diameter sorted patterned ground, and 53 54 27,28,29,30 55 108 palsas. A typical Beartooth Plateau surface is illustrated in Figure 2B. Permafrost has 56 57 58 59 5 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 6 of 42

1 2 3 109 been reported in several non-rock-glacier locations in the Beartooth Plateau at elevations 4 5 28-31 6 110 above 2950 m). 7 8 111 [Figure 2 near here] 9 10 11 112 3. METHODS 12 13 14 113 3.1 Rock glacier inventory 15 114  32 16 Digital aerial photos with 1 1 m resolution, flown in August 2005, were used to identify 17 18 115 possible rock glaciers in the study area. A total of 660 rock glaciers and rock-glacier complexes 19 For Peer Review 20 116 were identified and hand-digitized. Several criteria were utilized to ensure consistency in the 21 22 23 117 recognition of features as rock glaciers: 24 25 118 (1) Morphology. Rock glaciers appear as lobate or tongue-shaped flowing masses of ice 26 27 33 28 119 (Figure 2C), rock, and debris, and are morphologically distinct from talus fields, rockfalls, and 29 30 120 moraines.3 31 32 33 121 (2) Indications of motion. Signs of flow associated with rock glaciers include parabolic 34 35 122 34,35 36 ridges and furrows (Figure 2D) on better-developed features and a teardrop or ‘tongue’ 37 38 123 shape (Figure 2G) is often associated with smaller, less complex rock glaciers. 39 40 41 124 (3) Frontal slope. Active rock glaciers usually have steep frontal slopes (Figure 2E).36 42 43 44 125 (4) Debris provenance. Rock glaciers have identifiable debris sources (Figure 2F), such as 45 46 126 cirques or cliffs above them.33 47 48 49 127 (5) Positional relation to glacial cirques. The presence of a cirque glacier or glacial cirque 50 51 52 128 valley above a potential rock glacier (Figure 2G) is indicative of rock-glacier formation, based on 53 54 129 the model developed by Potter et al.16 55 56 57 58 59 6 60 http://mc.manuscriptcentral.com/ppp Page 7 of 42 Permafrost and Periglacial Processes

1 2 3 130 Figure 2 illustrates the primary morphological characteristics of rock glaciers in the study 4 5 6 131 area. 7 8 9 132 10 133 3.2 Topographic, geologic, and environmental parameters 11 12 134 Digital elevation models (DEMs) at 10  10 m resolution were obtained from the U.S. Geological 13 14 37 1 15 135 Survey. Slope and aspect layers were calculated from the DEMs using ArcGIS Spatial Analyst. 16 17 136 ArcGIS Solar Analyst was used to calculate incoming solar radiation, based on a DEM, at site- 18 19 For Peer Review 20 137 specific latitudes. A sun map of the sky was used to estimate mean annual incoming solar 21 22 138 radiation for the study area.38 Absaroka and Beartooth lithologies were extracted from Zientek 23 24 139 et al.39 Parameter data were extracted in ArcGIS for each pixel lying within each rock-glacier 25 26 27 140 polygon. Pixel values within each individual rock-glacier polygon were averaged using ArcGIS 28 29 141 Zonal Statistics. For analysis, means of each variable were used. 30 31 32 142 The direction faced by each rock glacier was calculated from “mean surface aspect” (the 33 34 35 143 average aspect of DEM pixels within a rock glacier polygon) and statistical procedures designed 36 37 144 for periodic (circular) data40,41,42 were applied to the resulting data set. The Kuiper and Watson 38 39 2 40 145 U tests for departure from uniformity (the null hypothesis) were applied to the empirical 41 42 146 frequency distributions of rock glacier orientation data for the two ranges. The two-sample 43 44 147 Uniform-Scores test was applied to examine the proposition that the empirical frequency 45 46 47 148 distributions of Absaroka and Beartooth rock glaciers differ. 48 49 50 149 Meteorological stations are scarce within the study area. Interpolated precipitation 51 52 53 150 estimates from the “Parameter – elevation Regressions on Independent Slopes Model” 54 55 56 1 ESRI, Redlands, CA. 57 58 59 7 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 8 of 42

1 2 3 151 (PRISM)43 for the Absarokas are approximately 100–130 cm yr-1 at the highest elevations, while 4 5 -1 6 152 the Beartooths receive an estimated 150–180 cm yr . PRISM used U.S. National Weather 7 8 153 Service observations of temperature and precipitation, and employed digital elevation models 9 10 11 154 (DEMs) to interpolate climatic parameters on varying timescales. This approach has been 12 13 155 shown to reproduce climate patterns in mountainous terrain better than many other 14 15 44 16 156 techniques. Averages of January and July temperatures during the 1991–2009 period, 17 18 157 calculated for the Monument Peak Snotel station (45.217oN, 110.333oW; 2697 m.a.s.l.) were 19 For Peer Review 20 158 -9°C and 12°C respectively.45 Descriptive statistics for the topographic and environmental 21 22 23 159 parameters are listed in Table 1. 24 25 160 [Table 1 near here] 26 27 28 161 29 30 162 3.3 Rock-glacier activity classification 31 32 163 Activity level was assessed in the field for 80 rock glaciers. An additional 40 rock glaciers were 33 34 35 164 classified by activity level using only aerial photos, DEMs, and prior knowledge of field sites. 36 37 165 Rock glaciers were evaluated according to a set of criteria derived from the literature (Table 2) 38 39 166 40 that relate surface characteristics to recent movement and thus determine whether a rock 41 42 167 glacier is modern or relict (this does not account for possible reactivation of “relict” features, 43 44 168 which can be initiated by decreased temperature or increased water supply).46 Specific criteria 45 46 47 169 used include: (a) shallower, less well-defined frontal slopes Figure 2H) that indicate loss of ice 48 49 170 cores36; (b) thermokarst development upslope of the rock-glacier terminus (Figure 2H), also 50 51 36 52 171 indicative of ice core loss ; and (c) encroachment of vegetation (Figure 2I), indicative of relict, 53 54 172 or at least inactive forms.36 55 56 57 58 59 8 60 http://mc.manuscriptcentral.com/ppp Page 9 of 42 Permafrost and Periglacial Processes

1 2 3 173 To estimate the activity status of the 540 rock glaciers not investigated in the field or 4 5 6 174 examined on air photographs, a logistic regression was performed using the 120 field- and 7 8 175 remotely-verified rock glaciers. The five variables listed in Table 2 (elevation, area, slope, 9 10 11 176 linearized aspect, potential insolation, and estimated precipitation), along with estimated 12 13 177 temperature data and lithology (coded as two dummy variables) were used to build the 14 15 16 178 regression model, which employed a backwards stepwise procedure. At each step the variable 17 18 179 with the least weight was eliminated from the model until a desired p value <0.05 was reached. 19 For Peer Review 20 180 Further details are provided in Seligman.20 Binary logistic regression produces logits, the 21 22 23 181 logarithmically transformed odds of whether a selected binary categorical variable will occur 24 25 182 based on input from independent variables.47 26 27 28 183 29 30 31 184 [Table 2 near here] 32 33 34 185 3.4 Elevation Trend 35 36 186 To assess if rock glaciers in the study area form part of a regional climate-related elevation 37 38 187 trend, data from several previous studies in the USA’s Pacific Northwest were used to examine 39 40 41 188 the relation between rock-glacier elevation and increasing distance from the Pacific Ocean. 42 43 44 189 A 1056 km transect was constructed from Mt. Cameron (47.82°N, 123.32°W) in the 45 46 190 Olympic Mountains of western Washington State to the approximate centroid of the combined 47 48 49 191 northern Absaroka and Beartooth study areas in the east (45.25°N, 110.00°W). The mean 50 51 192 elevation of a group of rock glaciers (1720 m) in the precipitation shadow of Mt. Cameron 52 53 48 54 193 forms the westernmost data point in the transect. Mean elevation of rock glaciers in the 55 56 194 Cascade Mountains of Washington State (2120 m) was derived from features inventoried by 57 58 59 9 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 10 of 42

1 2 3 195 Weidenaar49 in his “Lake Chelan”, “North Cascades Southern Part”, and “South Cascades” study 4 5 6 196 areas. Rock glaciers in Idaho’s Lemhi Range were reported as lying at elevations “>2600 m”. The 7 8 197 elevations of individual rock glaciers were not reported so that value was used.17 This group of 9 10 11 198 rock glaciers lies a substantial distance south of the transect; a cosine transformation was used 12 13 199 to project this location onto the transect line.50 Mean rock-glacier elevation was computed as 14 15 16 200 2760 m for lobate and tongue-shaped rock glaciers in the Tobacco Root Mountains of 17 18 201 southwestern Montana,51 and 2830 m in the combined Absaroka and Beartooth inventories. 19 For Peer Review 20 202 The average elevation of individual rock glaciers in the respective samples was used to compute 21 22 23 203 an agglomerated mean elevation for each sample (i.e., for each data point). 24 25 26 204 Because uncertainties associated with data grouping exist in both the independent 27 28 205 (latitudinal/longitudinal) and dependent (elevation) variables, error was partitioned between 29 30 52 31 206 the two variables using a reduced major axis (RMA) line to represent the relation between 32 33 207 distance along the transect and mean elevation at the sample locations. 34 35 36 208 37 38 39 209 4. RESULTS 40 41 210 4.1 Rock glacier distribution 42 43 211 Figure 3 shows the distribution of the 270 Absaroka and 391 Beartooth rock glaciers. 44 45 46 212 Topographic and climatic parameters are substantially different between the two mountain 47 48 213 ranges (Table 2). Beartooth rock glaciers generally lie at higher elevations (~200 m) than those 49 50 214 in the northern Absarokas (Figure 4; Table 1). This partly reflects the fact that parts of the 51 52 53 215 Beartooth Mountains are higher in elevation than the northern Absaroka Range, with many 54 55 216 peaks over 3800 m. Beartooth rock glaciers are also larger. Approximately 5% of Beartooth rock 56 57 58 59 10 60 http://mc.manuscriptcentral.com/ppp Page 11 of 42 Permafrost and Periglacial Processes

1 2 3 217 glaciers are larger than any found in the northern Absarokas. Slope angles of rock glaciers do 4 5 6 218 not differ significantly between ranges, with mean slopes of approximately 20°. 7 8 219 [Figures 3 and 4 near here] 9 10 11 220 Lithology is significantly different between the two ranges. Layered granitic gneiss 12 13 221 constitutes 90% of the bedrock in the Beartooths (pp. F15-F18)25 and nearly 90% of Beartooth 14 15 16 222 rock glaciers are derived from these and other less extensive metamorphic rocks. Although 17 18 223 some northern Absaroka rock glaciers have lithological composition similar to those of the 19 For Peer Review 20 224 Beartooths, almost half are volcanic in origin. A few rock glaciers in the northern part of both 21 22 23 225 ranges occur in rocks of plutonic igneous origin. 24 25 226 Florentine13 concluded that the largest proportion of rock glaciers in her southwest 26 27 28 227 Montana study area occurs in areas of foliated rocks, in which topography conducive to the 29 30 228 creation of rock glaciers is best developed. Strongly foliated rocks also provide abundant clastic 31 32 33 229 material to developing rock glaciers. Results from the current investigation are in agreement 34 35 230 with Florentine’s conclusions, with the majority of rock glaciers occurring in areas of layered 36 37 231 38 metamorphic rocks (Figure 5). 39 40 232 41 42 233 [Figure 5 near here] 43 44 45 234 46 47 235 4.2 Influence of environmental parameters 48 236 53 49 Morris concluded that preservation of ice cores within the rock glaciers of his southern 50 51 237 Colorado study area was influenced by rockfall intensity and topoclimatic parameters, including 52 53 238 elevation, reduction of incident radiation by topographic screening, and position of cirque 54 55 56 239 headwalls with respect to wind-drifting and snow avalanches. Other studies have examined 57 58 59 11 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 12 of 42

1 2 3 240 rock-glacier development and preservation through annual radiation receipts,17 lithology and 4 5 54 6 241 other geological controls, and morphology and topography. 7 8 242 Results from the directional statistical analysis indicate the operation of strong 9 10 11 243 topoclimatic controls over rock-glacier location in the northern Absarokas and Beartooths. Rock 12 13 244 glaciers in both ranges appear to be controlled by the same topoclimatic factors. They are most 14 15 16 245 common on N-NE facing exposures, although they occur over a wide range of aspect (Figure 6). 17 18 246 Statistical descriptors for the sample circular frequency distributions are nearly identical (Table 19 For Peer Review 20 247 3), and the relative numbers of rock glaciers in histogram bins around the circle are similar 21 22 23 248 between the two ranges. Results from the Watson U2 (pp. 180-18240; pp. 71)41 and Kuiper (pp. 24 25 249 173-18040; pp. 66-67)41 tests for preferred direction demonstrate that features in both ranges 26 27 28 250 depart significantly from the uniform distribution. Rock glaciers in both ranges exhibit a strong 29 30 251 preference for N to NE exposures, indicating that radiation receipts are an important factor in 31 32 40 41 33 252 determining their locations. The two-sample Uniform Scores test (pp. 197-201 ; pp. 122-123) 34 35 253 indicates that there is no statistical difference in the orientation of rock glaciers between the 36 37 254 38 northern Absaroka and Beartooth ranges (Table 3). Beartooth rock glaciers were estimated to 39 40 255 receive only about 3% higher levels of insolation than those in the northern Absarokas, 41 42 256 consistent with the result from the Uniform Scores test. Beartooth rock glaciers were estimated 43 44 45 257 to receive somewhat more (+14 cm yr-1) mean annual precipitation than those in the northern 46 47 258 Absarokas. 48 49 50 259 [Figure 6 and Table 3 near here] 51 52 260 53 54 55 261 4.3 Activity status 56 57 58 59 12 60 http://mc.manuscriptcentral.com/ppp Page 13 of 42 Permafrost and Periglacial Processes

1 2 3 262 Only elevation, a surrogate for lapse-rate influenced temperature, emerged from the 4 5 6 263 logistic regression as a strongly significant variable (inclusion of estimated temperature 7 8 264 involved problems of colinearity). A Hosmer and Lemeshow47 goodness-of fit-statistic was used 9 10 11 265 to test whether observed values of rock-glacier activity differed from predicted. Predicted 12 13 266 values did not differ from observed (p = 0.233). A traditional chi-squared test for model fit was 14 15 47 16 267 also employed, and showed a significant relation between predictor and response variables (p 17 18 268 <<0.05). The resulting equation was used to calculate probabilities for the “modern” activity 19 For Peer Review 20 269 classification for the remaining 540 rock glaciers, which were then mapped to show the 21 22 23 270 distribution of activity probability. 24 25 271 The resulting map (Figure 7) and histogram (Figure 8) of probabilities show substantial 26 27 28 272 differences between the two ranges. More than 30% of Beartooth rock glaciers have a 70% or 29 30 273 higher probability of being modern, while only 8% of northern Absaroka rock glaciers do. 31 32 33 274 Although elevation alone does not explain the variability in rock-glacier activities entirely, 34 35 275 results from the logistic regression supports its use to estimate and analyze rock-glacier 36 37 276 38 location. A larger proportion of rock glaciers in the Beartooths are of glaciogenic origin than in 39 40 277 the northern Absarokas, and this may be a contributing factor to the higher incidence of 41 42 278 “modern” rock glaciers in the Beartooth Range. 43 44 45 279 [Figures 7 and 8 near here] 46 47 280 48 49 50 281 4.4. Elevation trend 51 52 282 Results from the reduced major axis analysis demonstrate that a strong relation (r = 0.972) 53 54 55 283 exists between rock-glacier elevation and distance from the Pacific Ocean along the transect 56 57 58 59 13 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 14 of 42

1 2 3 284 (Figure 9). Mean rock glacier elevation rises at a rate of about 1.0 m km-1 over the transect, an 4 5 6 285 apparent response to the gradient of climatic continentality inland from the Pacific Ocean. 7 8 286 [Figure 9 near here] 9 10 11 287 12 13 288 5. DISCUSSION 14 15 289 5.1 Rock glacier elevation trend 16 17 18 290 Although a nearly 200 m difference exists between mean rock-glacier elevation in the 19 For Peer Review 20 291 Beartooth and northern Absaroka Ranges (Table 1), there is considerable overlap in their 21 22 23 292 altitudinal frequency distributions (Figure 4). The difference in mean elevation between the two 24 25 293 ranges appears to be controlled to a large extent by the existence of terrain at higher elevations 26 27 28 294 in the Beartooths than in the northern Absarokas, as detailed in Section 4.1. 29 30 295 In a broader context, however, the mean elevation of rock glaciers in the study area is 31 32 296 33 consistent with the gradient of rock-glacier elevation in the larger Pacific Northwest (PNW) 34 35 297 region of the USA (Figure 9). This reflects a regional response to climatic continentality, as is the 36 37 298 case with glacial cirques in the PNW (p. 72),55 and is consistent with Humlum’s56,57 38 39 40 299 demonstration of a close relation between the elevation trends of rock glaciers and glacial 41 42 300 equilibrium-line altitudes in Greenland. The rock-glacier elevation trend in the PNW is also 43 44 58 45 301 similar to the trends of other periglacial features, including cryoplanation terraces, 46 47 302 blockfields,50 solifluction features,59 and large-scale patterned ground in northwestern North 48 49 60 50 303 America and elsewhere. Viewed from this broader perspective, the difference in mean rock- 51 52 304 glacier elevation between the Beartooths and northern Absarokas is a reflection of relatively 53 54 305 local variations in topography, topoclimate, and lithology. 55 56 57 58 59 14 60 http://mc.manuscriptcentral.com/ppp Page 15 of 42 Permafrost and Periglacial Processes

1 2 3 306 The relation between rock-glacier elevation and distance from moisture sources 4 5 6 307 illustrated in Figure 9 should be considered the result of a preliminary analysis based on sparse 7 8 308 data, and without differentiation between active/inactive features, glaciogenic/periglacial 9 10 11 309 origin, or feature morphology. The increasing availability of detailed rock-glacier inventories in 12 13 310 North America2 should facilitate the application of sophisticated spatial-analytic techniques in 14 15 16 311 the near future. 17 18 312 19 For Peer Review 20 313 5.2 Glacial-Periglacial Transition 21 22 23 314 Evaluation of rock-glacier locational parameters in the Beartooth and northern Absaroka ranges 24 25 315 provides insights into the glacial history of the region. Assuming that both ranges were subject 26 27 28 316 to similar paleoclimatic trends owing to their proximity, deductions can be made regarding 29 30 317 climatic effects on rock-glacier genesis, as well as controls on glacial landscape evolution. 31 32 61 33 318 According to Locke, East Grasshopper Glacier, one of the larger glaciers in the 34 35 319 Beartooth Range, currently falls below glacial climatic boundaries. This conclusion is supported 36 37 320 th 62 38 by research documenting substantial thinning of this glacier since the mid-20 century. The 39 40 321 Beartooth Range currently contains only a few cirque glaciers similar to the Grasshopper Glacier 41 42 322 (71 according to Graf63 and 21 according to Locke),61 and glaciogenic rock glaciers are presently 43 44 45 323 the dominant glacial feature in many of these valleys. In contrast, the entire northern Absaroka 46 47 324 Range currently contains only two possible cirque glaciers (on northern aspects of Mt. Cowen 48 49 50 325 and Marten Peak), which may more appropriately be classified as snowfields (nine glaciers were 51 52 326 present on these peaks according to Graf).63 This relative distribution provides important 53 54 55 56 57 58 59 15 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 16 of 42

1 2 3 327 context for analyzing potential shifts along the continuum from glacial to periglacial 4 5 64 6 328 landscapes in these two proximal mountain ranges. 7 8 329 Valleys in the Beartooth Mountains fit into a geomorphic model in which a landscape 9 10 65 11 330 with a significant glacial component is transformed into one that is increasingly periglacial. 12 13 331 Most rock glaciers in the Beartooths have characteristics indicating a glaciogenic origin, as they 14 15 16 332 are large in size and often have formed below cirque glaciers. Periglacial rock glaciers are, 17 18 333 however, also common in the Beartooths. 19 For Peer Review 20 334 Graf63 described cirque glaciations as a series of cyclic events. As local climate becomes 21 22 23 335 more glacial, accumulation exceeds ablation, and glaciers grow. If climate then becomes milder, 24 25 336 ablation is greater than accumulation and glaciers recede. Local topography then exerts 26 27 28 337 increasing influence on glacial systems relative to macroclimate through shading by cirque 29 30 338 walls, topographically induced snow accumulation, and increased avalanching.63 At this point in 31 32 33 339 deglaciation, glaciers are at a minimum and are either retreating or disappearing, leaving more 34 35 340 cirque headwall available for erosion. Eroded debris is subsequently added to the persisting 36 37 341 38 glacial ice below, and as debris accumulation exceeds ice accumulation, glaciogenic rock 39 40 342 glaciers can form. Through this process, glaciogenic rock glaciers are one step in the evolution 41 42 343 of glacial landscapes. 43 44 45 344 Periglacial rock glaciers are the result of excessive debris accumulation in a cold, 46 47 345 nonglacial environment54 owing to avalanching of ice and rock. Consistently cold temperatures, 48 49 66 50 346 not glacial geomorphology, constitute a primary control on formation (cf. ). In the northern 51 52 347 Absarokas, most rock glaciers appear to be of periglacial origin, although glaciogenic rock 53 54 15,16 55 348 glaciers can also be found in the Absaroka Range. Periglacial rock glaciers are present on 56 57 58 59 16 60 http://mc.manuscriptcentral.com/ppp Page 17 of 42 Permafrost and Periglacial Processes

1 2 3 349 valley sides and may have begun their initial growth as pronival ramparts during more recent 4 5 6 350 cold events, as hypothesized for morphologically similar rock glaciers in the nearby Lemhi 7 8 351 Range.17 9 10 11 352 Analysis of the characteristics between ranges supports a conceptual model involving an 12 13 353 ongoing shift from predominantly glacial to predominantly periglacial landscape processes in 14 15 16 354 Beartooth valleys. Although there are many similarities between rock glaciers in the northern 17 18 355 Absarokas and the Beartooths, those in the latter range are higher in elevation, receive more 19 For Peer Review 20 356 precipitation, and are subject to lower annual temperatures.20 As warming followed the glacial 21 22 23 357 maximum, climatic conditions in the Beartooths maintained a higher likelihood of sustaining 24 25 358 glacial conditions and preserving glacial ice relative to the northern Absarokas. With continued 26 27 28 359 warming and glacier recession, however, the shift toward periglacial conditions is becoming 29 30 360 more apparent. 31 32 61,67 33 361 While glaciers are barometers of change in precipitation and temperature, 34 35 362 glaciogenic rock glaciers, by their existence, signal a decline in precipitation or an increase in 36 37 363 38 temperature relative to previous conditions. In some areas, their frequent occurrence at 39 40 364 elevations similar to glaciers appears to reflect the onset of conditions that are too dry to 41 42 365 maintain contemporary glaciers.68,69 Moreover, owing to the formation of an insulating rock 43 44 45 366 mantle, rock glaciers may exhibit a slow response to changes in temperature. A marked 46 47 367 increase in annual temperature would, therefore, have to persist over decades or even 48 49 70 50 368 centuries to yield a significant response. 51 52 369 Temperature increases in the instrumental climate record over the past century in areas 53 54 71 55 370 of the nearby Canadian Rockies correspond to a decline in glacial mass balance. Similarly, 56 57 58 59 17 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 18 of 42

1 2 3 371 anomalous interaction of high summer temperatures and low winter snow accumulation has 4 5 6 372 led to unprecedented glacial recession in Glacier National Park, Montana, beginning in the early 7 8 373 20th century.72 Increased summer temperatures affecting glacier recession in other Rocky 9 10 11 374 Mountain areas are likely to also be the source of changes in northern Absaroka and Beartooth 12 13 375 high-elevation areas. In the wake of widespread glacier recession, rock glaciers may become 14 15 16 376 the principal vestiges of glacial ice in the Beartooth region, as they appear to currently be in the 17 18 377 northern Absarokas. 19 For Peer Review 20 21 378 22 23 379 6. CONCLUSIONS 24 25 380 More than 650 rock glaciers were mapped within the study area and described using several 26 27 28 381 topographic and climatic variables. Distinct differences are apparent between northern 29 30 382 Absaroka and Beartooth rock glaciers with respect to size, elevation, precipitation, and 31 32 33 383 lithology. The Beartooth rock glaciers are larger, higher in elevation, and receive more 34 35 384 precipitation. Inferences from these comparisons indicate that, while Beartooth glacial 36 37 385 38 geomorphology is shifting from glacial to periglacial, the higher elevations of the northern 39 40 386 Absarokas are already governed largely by periglacial conditions. 41 42 387 Basic understanding of these rock glaciers is important because glacial decline is 43 44 45 388 increasing in response to climate warming. Rock glaciers may soon become an important 46 47 389 source of meltwater in the region. The inventory described here has potential to become a 48 49 50 390 useful source of information about water resources in the Middle and Northern Rocky 51 52 391 Mountains. Results from the analyses presented here can also serve as baseline data for 53 54 55 392 assessing the importance of rock glaciers with respect to alpine stream ecology and 56 57 58 59 18 60 http://mc.manuscriptcentral.com/ppp Page 19 of 42 Permafrost and Periglacial Processes

1 2 3 393 biodiversity,73 and climatic-driven changes74 in the northern Absaroka and Beartooth 4 5 6 394 Mountains. 7 8 395 9 396 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 19 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 20 of 42

1 2 3 397 4 5 398 ACKNOWLEDGMENTS 6 399 Dan Seifert of the Custer National Forest Ranger District and Don Evans from the U.S. Forest 7 8 9 400 Remote Sensing Applications Center provided funding and aerial photos. Ryan Rock (University 10 11 401 of Montana) provided helpful advice and assistance with literature. ZMS expresses special 12 13 14 402 thanks to Greg Pederson for providing initial inspiration. We are grateful to two anonymous 15 16 403 reviewers for comments and suggestions that led to improvements in the paper. 17 18 404 19 For Peer Review 20 21 405 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 20 60 http://mc.manuscriptcentral.com/ppp Page 21 of 42 Permafrost and Periglacial Processes

1 2 3 406 4 5 407 REFERENCES 6 7 1 Kaufmann V. The evolution of rock glacier monitoring using terrestrial photogrammetry: The 8 9 example of Äusseres Hochebenkar rock glacier (Austria). Austrian Journal of Earth 10 11 12 Sciences. 2012; 105(2): 63-77. 13 14 2 Jones DB, Harrison S, Anderson K, Betts RA. Mountain rock glaciers contain globally significant 15 16 17 water stores. Nature Geosciences, 2018; 8: 2834. DOI:10.1038/s41598-018-21244-w 18 19 3 Millar C, Westfall RD. Rock-glaciersFor Peer and related Review periglacial landforms in the Sierra Nevada, CA, 20 21 22 USA: Inventory, distribution and climatic relationships. Quaternary International, 2008; 23 24 188(1): 90-104. 25 26 4 Kellerer-Pirklbauer A, Lieb GR, Kleinferchner H. A new rock glacier inventory of the eastern 27 28 29 European Alps. Austrian Journal of Earth Sciences, 2012; 105: 78-93. 30 31 5 Scotti R, Brardinoni F, Alberti S, Frattini P, Crosta GB. A regional inventory of rock glaciers 32 33 34 and protalus ramparts in the central Italian Alps. Geomorphology, 2013; 186: 136-149. 35 36 DOI: 10.1016/j.geomorph.2012.12.028 37 38 6 39 Rangecroft S, Harrison S, Anderson K, McGrath J, Castel AP, Pacheco P. A first rock glacier 40 41 inventory for the Bolivian Andes. Permafrost and Periglacial Processes, 2014; 25(4): 333- 42 43 44 343. DOI: 10.1002/ppp.1816 45 46 7 Janke JR, Ng S, Bellisario A. An inventory and estimate of water storage in firn fields, glaciers, 47 48 debris-covered glaciers, and rock glaciers in the Aconcagua River Basin, Chile. 49 50 51 Geomorphology, 2017; 296: 142-152. DOI: 10.1016/j.geomorph.2017.09,002 52 53 54 55 56 57 58 59 21 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 22 of 42

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1 2 3 408 4 5 409 6 410 Absaroka Beartooth Difference 7 411 Rock Glaciers Rock Glaciers (Absaroka minus Beartooth) 8 412 9 413 mean 2732 2929 197 10 11 414 Elevation (m) min 2093 2239 146 12 415 max 3072 3443 371 13 416 14 417 15 16 418 mean 65,274 143,637 78,363 2 17 419 Area (m ) min 1,444 3,235 1,792 18 420 Max 471,480 3,281,408 2,809,928 19 421 For Peer Review 20 422 21 22 423 mean 19 20 1 23 424 Slope min 5 5 0 24 425 (degrees) max 35 38 3 25 426 26 27 427 28 428 29 429 Mean 1337 1381 44 30 430 Insolation min 923 987 64 31 431 (kWh/m2) max 1674 1712 68 32 33 432 34 433 35 434 36 435 mean 89 103 14 37 436 38 Precipitation min 52 69 17 39 437 (cm) max 117 169 52 40 438 41 439 42 440 43 44 441 45 442 Table 1. Mean, minimum, and maximum values of topographic and environmental parameters, 46 443 Absaroka and Beartooth rock glaciers. 47 444 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Page 31 of 42 Permafrost and Periglacial Processes

1 2 3 445 Modern, Active Modern, Possibly Inactive Relict 4 5 446 6 447 Surface smooth can be smooth with blocky dominantly blocky; has 7 448 sections; has circular or heavily pitted surface 8 449 elongated pits indicative of thermokarst 9 450 10 11 451 Lichen little or no lichen crests of ridges lichenized; rock surfaces completely 12 452 furrows lichen-free lichen covered 13 453 14 454 15 For Peer Review 16 455 Surface Clasts angular, unweathered, less sorted; slightly highly weathered; unsorted 17 456 size sorted weathered 18 457 19 458 Front and Side Slopes ≥ 35o ≥ 35o < 35o 20 459 21 22 460 Frontal Slope Stability unstable, with large fresh less sorted; slightly weathered low angled; stable 23 461 angular clasts at base 24 462 25 463 26 27 464 Vegetation no vegetation cover partly or fully vegetated well-developed soils; 28 465 all surfaces colonized by 29 466 vegetation 30 467 31 468 32 33 469 34 470 Table 2. Criteria used to assess rock-glacier activity, based on those developed by Clark et al.,Error! Bookmark not defined. Chueca and 35 471 Julian,35 Johnson et al.,17 Millar and Westfall,3 and Roer and Nyanhuis.36 See Seligman20 for further details. 36 472 37 38 39 40 41 42 43 44 45 http://mc.manuscriptcentral.com/ppp 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Permafrost and Periglacial Processes Page 32 of 42

1 2 3 473 4 5 2 6 474 Range n mean normalized median circular circular Watson U Kuiper 7 475 vector resultant length variance std. dev. 8 476 ‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗‗ 9 477 10 478 Absaroka 270 39.0o 0.182 40o 0.818 105.7 0.504* 2.506† 11 12 479 13 480 Beartooth 391 36.0o 0.174 45o 0.826 107.2 0.631* 2.680† 14 481 For Peer Review 15 482 Combined 661 37.6o 0.178 16 17 483 Sample 18 484 19 485 20 486 †significant at p <0.005 21 22 487 *significant at p <0.01 23 488 24 489 25 26 490 27 491 Two-sample Uniform Scores (Mardia-Watson-Wheeler) test for equality of populations 28 492 29 493 W = 0.163 p = 0.922 30 31 494 32 495 Table 3. Results from circular statistical tests. One-sample (Watson U2 and Kuiper) circular statistical tests indicate that rock glacier 33 496 orientation in both ranges differ significantly from the null hypothesis that samples were drawn from a uniform distribution. Sample 34 497 statistics are very similar for the two ranges. Formal results from the two-sample Uniform Scores test indicate no difference in 35 498 40 41 36 orientation between rock glaciers in the two ranges. Procedures used are described in detail in Mardia, Fisher, and Kovach 42 37 499 Computing Services. 38 39 40 41 42 43 44 2 45 http://mc.manuscriptcentral.com/ppp 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Page 33 of 42 Permafrost and Periglacial Processes

1 2 3 500 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 34 of 42

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 Figure 1. Shaded relief map of the study area (dotted outline), showing location north of Yellowstone 31 National Park (dashed), along the Montana/Wyoming state border (long dashed line), with highways, cities, 32 and locations mentioned in the text labeled. Inset map shows location of study area in the northwestern 33 USA. 34 168x121mm (300 x 300 DPI) 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Page 35 of 42 Permafrost and Periglacial Processes

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Figure 2. Morphological characteristics of rock glaciers and other periglacial forms in the study area. (A) 34 Rock Creek Valley near U.S. Highway 212 in southeast portion of study area. Note cirque, possibly occupied 35 by a glaciogenic rock glacier, on far valley wall, and talus forms in foreground. Photo by FEN, September 36 1985. (B) Plateau-like inter-valley surface near U.S. Highway 212 and Beartooth Basin Summer Ski Area. Note disintegrating tor and large-diameter sorted stripes. Photo by FEN, July 1978. (C) Emigrant Peak Rock 37 Glacier, showing ridge-and-furrow microtopography indicative of movement. (D) Beartooth Mountain Rock 38 Glacier, a glaciogenic feature, showing well-developed indications of activity. (E) Silver Run Rock Glacier, 39 developed from ice glacier at higher elevation. (F) The Bear’s Tooth Rock Glacier, showing steep frontal 40 slope indicative of ice core and movement. (G) Arrastra Lake Rock Glacier, a tongue-shaped rock glacier 41 ~1.5 km N of Mineral Mountain, showing sources of clastic material from backwall. (H) East Fork Emigrant 42 Creek Rock Glacier, inactive rock glacier, showing shallow slopes, thermokarst pits, and encroachment by trees. (I) Saddleback Mountain Rock Glacier, inactive rock glacier, showing well-established forest atop the 43 rock glacier. Photos C through I by ZMS, Summer 2008. 44 45 165x135mm (299 x 299 DPI) 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 36 of 42

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 Figure 3. Map showing hand-digitized rock glaciers in the northern Absaroka (left, light gray) and Beartooth 31 (right; dark gray) ranges. The study area (dotted), Yellowstone National Park (dashed), the 32 Montana/Wyoming state borders (long dashed line), are shown and highways and cities labeled. Inset map 33 shows location of study area in the northwestern USA. 34 168x121mm (300 x 300 DPI) 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Page 37 of 42 Permafrost and Periglacial Processes

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 Figure 4. Percentage frequency of mean elevation of rock glaciers in the northern Absaroka and Beartooth 29 ranges A difference of means test indicated that rock-glacier elevation is significantly different in the two 30 ranges (p <0.0001). 31 32 79x53mm (300 x 300 DPI) 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 38 of 42

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 Figure 5. Percentage frequency of rock glaciers by lithology in the northern Absaroka and Beartooth ranges.

28 29 79x49mm (300 x 300 DPI) 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Page 39 of 42 Permafrost and Periglacial Processes

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 Figure 6. Percentage frequency of aspect (15° bins) of rock-glaciers in the (A) northern Absaroka and (B) 27 Beartooth Ranges. 28 81x48mm (300 x 300 DPI) 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 40 of 42

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 Figure 7. Map of the probabilities of rock glaciers being classified as “modern” (Table 2). The study area 31 (dotted), Yellowstone National Park (dashed), and Montana/Wyoming state border (long dashed line), are 32 shown and highways and cities labeled. Inset map shows location of study area in the northwestern USA. 33 168x121mm (300 x 300 DPI) 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Page 41 of 42 Permafrost and Periglacial Processes

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 Figure 8. Percentage frequency of the probability of rock glaciers predicted to be “modern” in the Absaroka 28 and Beartooth ranges. 29 79x49mm (300 x 300 DPI) 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp Permafrost and Periglacial Processes Page 42 of 42

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 Figure 9. (A) Map of rock-glacier locations along a linear transect from the Olympic Mountains of Washington 46 state to the northern Absaroka/Beartooth study area in Montana. Data from additional transect locations in 47 the Cascades, Lemhi,and Tobacco Root Mountains were used. See text for details. (B) Graph of the elevations of mean rock-glacier elevation against distance from Pacific moisture sources along the transect 48 in (A). Reduced major axis line indicates that rock-glacier elevation increases at a rate of 1.04 m km-1 from 49 west to east along the transect.. 50 51 79x114mm (300 x 300 DPI) 52 53 54 55 56 57 58 59 60 http://mc.manuscriptcentral.com/ppp