Clyde Wahrhaftig and Allan Cox (1959) Rock glaciers in the Alaska Range. Bulletin of the Geological Society of America 70(4): 383

Abstract

Rock glaciers are one of the most prominent geomorphic features in high-elevation areas and affect numerous hydrologic, ecologic, and geomorphic processes. However, little scientific attention was focused on rock glaciers during the first part of the 20th century. In 1959, Clyde Wahrhaftig and Allan Cox published a paper titled ‘Rock glaciers in the Alaska Range’, which initiated worldwide interest in these features and a subsequent surge of publications addressing rock glaciers. Wahrhaftig and Cox (1959) provided a detailed and encompassing study on rock glacier features, origins, classifications, relations to climate, movement, and composition. Their data and descriptions established a firm basis for further advancement of rock glacier research. This paper aims to assess the influence that Wahrhaftig and Cox (1959) had on subsequent publications and studies of rock glaciers.

Keywords

classics revisited geology geomorphology rock glaciers Wahrhaftig and Cox

I Rock glaciers

Given the influence and prominence of rock glaciers in high mountain environments, it is difficult to imagine that these masses of ice-cored or ice-cemented rock debris received such limited attention in the first half of the 20th century. Rock glaciers are geophysically complex features that influence geomorphic, hydrologic, and ecologic processes. They serve as one of the most influential geomorphic components in many alpine areas (Owen and England, 1998), and are found in locations of high elevation throughout the world (e.g. Berger et al., 2004; Johnson et al., 2007; Monnier et al., 2011).

Rock glaciers also have ecological influences (Barsch, 1996) and may be utilized for human activities (Burger et al., 1999). One ecologic example is that they serve as habitat to pikas (Millar and Westfall, 2010), which utilize the cooler air temperatures often found within rock glaciers (Millar et al., 2012). Pikas are threatened by the advancement of warmer temperatures upslope (Butler, 2012; Hafner, 1994; Wei-Dong and Smith, 2005) and rock glaciers will likely become increasingly important for pika habitat. Although often found in remote high-elevation areas, rock glaciers are also used by humans. Rock glaciers have served as foundations to support ski towers, dam abutments, and tunnel portals. Burger et al. (1999) evaluated rock glaciers as an engineering feature, and recognized the importance of identifying them. They concluded that rock glaciers, which are often unstable in the long term, should not serve as support for structures. However, rock glaciers do provide a quality source of drinking water, essentially serving as an aquifer, in alpine areas (Burger et al., 1999). Rock glaciers, being dependent on the formation and maintenance of ice, are sensitive to climate conditions (Brazier et al., 1998; Clark et al., 1996) and may be affected by global climate change (Lugon and Stoffel, 2010; Roer et al., 2008). For this reason, among those mentioned above, it is especially important to identify and classify rock glaciers, and Wahrhaftig and Cox (1959) provided the first thorough publication on this topic. Before Wahrhaftig and Cox’s (1959) 63-page article, recognition, identification, classification, and terminology of rock glaciers were limited.

II The influence of Wahrhaftig and Cox (1959)

Described in the literature as ‘the single most influential paper on rock glaciers’ (Berthling, 2011: 98), Wahrhaftig and Cox’s 1959 paper titled ‘Rock glaciers in the Alaska Range’ provided the first cohesive, thorough description of rock glacier characteristics and movement. This paper established a solid foundation for the classification and processes of rock glaciers, igniting the study of rock glaciers for decades to follow. Capps (1910) first introduced the term ‘rock glacier’ 49 years prior to Wahrhaftig and Cox’s 1959 publication, and others had previously published on rock glaciers (e.g. Brown, 1925; Hollingworth, 1934). However, none experienced the lasting influence that Wahrhaftig and Cox (1959) had on this field of study. The large impact this paper had may be attributed to the great detail and quantity of data it provided, the descriptions of different forms of rock glaciers, and the solid explanation and justification in describing processes. Wahrhaftig and Cox’s (1959) most lasting legacy may not even be the rich data set and detailed information that they published, but possibly the fact that this paper spawned worldwide interest in, and turned attention to, rock glaciers.

Before the mid-1990s, literature on rock glaciers was limited. According to the review of rock glacier literature provided in Wahrhaftig and Cox (1959), only 27 papers were published that even mentioned or alluded to rock glaciers before 1959, and many of these publications did not use the term rock glacier (Brown, 1925; Cross and Howe, 1905). Instead, descriptive terms such as ‘rock stream’ and ‘fossil glacier’ were used in the early literature. Science Direct revealed only one paper when searching for ‘rock glaciers’ between 1900 and 1960 (Hollingworth, 1934). The first publication on rock glaciers was by Spencer (1900), although he did not use the term rock glacier. Capps (1910) applied the term rock glacier and described how they differed from ice glaciers, provided indications of movement, and presented numerous photographs. Although his article was important to subsequent studies on rock glaciers, including Wahrhaftig and Cox (1959), and their identification, Capps (1910) did not provide detailed measurements or the extensive descriptions and classifications. Therefore, Capps (1910) did not experience the enduring influence on the field of rock glacier study to the extent of Wahrhaftig and Cox (1959).

Evidence of this lasting impact is apparent in the research record of rock glaciers. Following the paper’s 1959 publication, interest in rock glacier research dramatically increased around the world. A search for the phrase ‘rock glaciers’ in Google Scholar revealed that the number of publications more than doubled between the decades of 1950–1959 and 1960–1969 (Figure 1). A basic search of the term ‘rock glaciers’ on Science Direct yielded 898 articles that were published in less than a 60-year timespan from 1960 to the present. At least some of this increase, it must be noted, is probably because of the general surge in publications and scientific interest that was occurring within many fields. Nonetheless, the number of Wahrhaftig and Cox (1959) citations indicates that this article did have significant influence on the study of rock glaciers. Google Scholar lists a total of 282 articles that have cited Wahrhaftig and Cox (1959) – on such topics as the origins of rock glaciers, their forms and movement, climate history, and the idea of ice and water on Mars (e.g. Berthling et al., 1998; Blagbrou and Farkas, 1968; Kääb et al., 1997; Karlén, 1973; Squyres and Carr, 1986; Wright, 1961) (Table 1). Interestingly, citations in journals outside of the discipline of earth sciences, such as Computers and Electronics in Agriculture (Willers et al., 2012), also reference Wahrhaftig and Cox (1959). Even rock glacier articles that do not cite Wahrhaftig and Cox (1959) directly likely reference a paper that does (e.g. Millar et al., 2012; Monnier et al., 2011). Including first- and second-generation citations, the Web of Science lists a total of 2,223 articles that cite Wahrhaftig and Cox (1959).

Figure 1.

Number of publications per decade that mention ‘rock glaciers’.

Table 1.

Publication topics that cite Wahrhaftig and Cox (1959). Articles were categorized by their apparent primary focus into topics that I delineated based on the more common themes of the papers.

Topic	1959–69	1970–79	1980–89	1990–99	2000–09	2010–12
Tectonics	1	0	0	2	0	0
Rock debris, landslides	2	4	8	2	3	2
Regional studies	2	3	1	0	8	0
Distribution of rock glaciers	1	0	3	1	7	4
Regional rock glaciers	3	10	5	9	16	4
Periglacial studies	2	1	0	0	3	1
Climate/paleoclimate	1	3	2	4	9	1
Mars/outer space	0	2	4	3	9	3
Dating methods	0	1	2	2	2	0
Permafrost studies	0	5	2	2	2	2
Rock glacier movement/dynamics	0	1	1	5	14	4
Erosion	0	1	1	0	4	0
Rock glacier and ice glacier relationships	0	1	1	0	0	0
General rock glacier studies	0	1	3	1	0	0
Sediment and ice analysis/structure	0	0	3	6	9	1
Terminology	0	0	1	2	0	1
Micro-topography	0	0	0	0	3	0
Other	3	4	3	4	6	0

The thoroughness and attention to detail that characterizes Wahrhaftig and Cox’s article is a likely contributing factor to its extensive influence. Wahrhaftig and Cox’s unassuming and almost conversational writing style probably also aided in the dissemination of their knowledge. The article was written in a clear, straightforward, and honest manner as they provided explanations and descriptions of rock glaciers. From the abstract to the methods and figures, details and vivid descriptions were provided in a clear and easily comprehensible style. Wahrhaftig and Cox (1959) provided an unparalleled evaluation of rock glacier characteristics, locations, and movement within the central Alaska Range. They collected data on approximately 200 rock glaciers during the 1950s through fieldwork, aerial photographs, and topographic maps.

The extent of information and detailed descriptions found in this article is not surprising when considered in regard to the character of both Wahrhaftig and Cox, and their legendary drive for excellence. According to an ‘In memoriam’ piece on the University of California’s website (Christensen et al., 2005), Wahrhaftig was ‘conscientious beyond the call of duty’ and was known for his energy, drive, and curiosity (Figure 2). Employed by the United States Geological Survey (USGS) from 1941 until his death in 1994, Wahrhaftig spent much time in Alaska collecting field data. He also worked at UC Berkeley from 1960 until 1982. His personal attributes of character and his dedication to the USGS and solid scientific study are evident throughout this classic paper. Cox also had numerous career achievements and was noted for his personal attributes (Kruaskopf). He completed his PhD in geology at UC Berkeley and while a student, as well as in following years, he accompanied Wahrhaftig on field trips to Alaska. He focused his studies on rock magnetism while he worked for the USGS and subsequently as a professor at Stanford University, where he was recognized for his friendliness and teaching, and his ability to inspire students to perform their best. Konrad Krauskopf (no date) stated, in a biographical memoir for Cox, that he exhibited an ‘extraordinary combination of scientific acumen, humility, concern for his fellows, and love of the natural world’.

Figure 2.

Clyde Wahrhaftig.

III The contribution of Wahrhaftig and Cox (1959)

Wahrhaftig and Cox (1959) included a table of contents that alludes to the great amount of information contained within this article. This paragraph and the following provide a brief overview of the content and format of Wahrhaftig and Cox (1959). They began their article by providing a summary of the rock glacier literature and introduced several inconstancies regarding rock glaciers at that time. They subsequently described the topographic setting and climate of their study sites before introducing the general characteristics and features of the rock glaciers in their study. Descriptions were provided on the three types of rock glacier identified, the debris that forms the rock glaciers, vegetation found on rock glaciers, and microrelief features. They described, in great detail, rock glacier movement, rates, and velocities for different locations within a rock glacier. Their data supported the idea that rock glacier movement was a deformational process of interstitial ice. They then compared the elevational locations of rock glaciers and ice glaciers to evaluate the influence of climate on each. One of the greatest differences was that southward-facing rock glaciers were only 100 and 200 ft higher in elevation than northward-facing rock glaciers, compared to a 2000 ft difference found with ice glaciers.

Wahrhaftig and Cox (1959) subsequently described the debris of rock glaciers, including the debris source and structure. They stated that the debris comes solely from the cliffs at the head of the rock glacier, and that the debris retains the same geology even as they move over areas of different lithology. The rock glaciers were found to contain two primary layers based on debris – an upper layer of coarse blocky material and an underlayer of finer sediments. Similarly, Wahrhaftig and Cox (1959) described the ice component of rock glaciers. Ice was found at both the rock glacier head and front, and probably originated from a combination of compacted snow, freezing water from melted snow or rain, or groundwater. They evaluated rock glacier distributions in regard to bedrock types and found strong associations. In their introductory description of rock glaciers, Wahrhaftig and Cox (1959) noted that microrelief on the upper surface was ‘among the most striking characteristics of rock glaciers’ (p. 392), and described the measurements of features such as furrows and ridges, which were found on most of the rock glaciers in their study. They attributed the microrelief to processes related to the accumulation or loss of ice, which resulted in pits and longitudinal ridges and furrows, and of the rock glaciers’ movement, which produced transverse ridges and furrows, some longitudinal ridges and furrows, lobes, and crevasses. Over half of the rock glaciers in Wahrhaftig and Cox’s (1959) study were inactive, which were identified by their covering of lichens and turf and a gentle slope between the front and upper surface. They also related rock glacier motion to global climate conditions, and subsequently rock glacier erosion and debris, which are linked to rock glacier movement.

Wahrhaftig and Cox provided unparalleled information for the 1950s on rock glacier movement, erosional influence, and measurements. Researchers still recognize the difficulty in identifying rock glaciers and understanding their ice structure, dynamics, and past movements (Evin, 1993; Hauck and Kneisel, 2008; Lugon and Stoffel, 2010; Millar et al., 2012; Ribolini et al., 2007). Only recently have advancements in methods made assessing interstitial ice dynamics, structure and origins, and dating easier and more accurate (Hauck and Kneisel, 2008; Monnier et al., 2011; Ribolini et al., 2007). Ground-penetrating radar, advanced photogrammetry methods, and remote sensing techniques are now applied to measure variables that were assessed by Wahrhaftig and Cox with crude field measurements, black and white aerial photographs, and topographic maps. Even in such conditions, Wahrhaftig and Cox made extensive measurements and greatly advanced understanding of rock glaciers. Their detailed observations and all-encompassing data yielded information never before recorded and a more comprehensive and accurate understanding of rock glacier processes. The sheer number of rock glaciers that they analyzed enabled them to characterize and classify these features into categories and descriptions still used today.

Wahrhaftig and Cox (1959) studied and influenced many aspects of the understanding of rock glaciers. I have selected three topics to briefly focus on in this paper – one that Wahrhaftig and Cox (1959) greatly influenced, a second that has received relatively little attention, and a third that is garnering increasing attention. The first topic discussed is rock glacier formation and classification, and is one of the areas in which Wahrhaftig and Cox (1959) had the most lasting and permeating influence. The second topic – erosion by rock glaciers – is one they addressed and is an important factor in high-elevation areas, but has been comparatively neglected in the literature. Conversely, the third topic – climate and rock glaciers – has received increasing attention. Wahrhaftig and Cox (1959) recognized the relation between rock glaciers and climate and, unlike erosion, this topic has become one of the prime subjects in regard to the study of rock glaciers. Relationships between rock glaciers and climate will probably continue to be popular in regard to climate change, rock glacier movement, and ecological habitat.

1 Origins and classifications of rock glaciers

Wahrhaftig and Cox (1959) served as a key turning point in the modern understanding of rock glacier development, and formed the basis of one of two theories commonly accepted as the origins of rock glaciers. In their article, they noted the plethora of hypotheses regarding the formation of rock glaciers at that time, and stated that the documented movement of rock glaciers discounted many of the early ideas of their origins. Alternatively, Wahrhaftig and Cox (1959) put forth the idea that rock glaciers form from accumulations of debris and interstitial ice. Therefore, conditions necessary for their formation must provide ample rock debris/talus and a climate conducive to the formation of ice among the debris. This theory was more inclusive than previous ideas, which included postulations that rock glaciers formed from terminal moraine debris that filled with mud and clay (Chiax, 1923), springs that supplied water which later froze to rock debris (Tyrrell, 1910), landslides (Howe, 1909), and unusual moraines (Cross and Howe, 1905). The origins of rock glaciers are still being debated in the current literature (Monnier et al., 2011), but two broad categories are recognized – the ideas that rock glaciers form from periglacial processes (Ballantyne and Harris, 1994; Vitek and Giardino, 1987) or that they transform from glacial to periglacial (Berger et al., 2004; Berthling, 2011; Owen and England, 1998; Potter, 1972; Shroder et al., 2000). Articles that postulate the periglacial origins often hark back to the ideas put forth by Wahrhaftig and Cox (1959) (Barsch, 1992, 1996; Haeberli, 1985, 1990). Other definitions, however, indicate that rock glaciers are neither fully periglacial nor glacial (Berthling, 2011) and that a continuum between the two exists and complicates the issue (Giardino and Vitek, 1988; Ribolini et al., 2010). Berthling (2011) proposed the idea of cryo-conditioned landforms, in which ground and surface thermal regimes control the distributions of rock glaciers.

Wahrhaftig and Cox (1959) found that microscale factors of topography and lithology influenced the distribution of rock glaciers, and were among the first to note the influence of lithology on the formation of rock glaciers. They stated that rock glaciers were much more common in areas where the bedrock weathered into blocky debris rather than into platy rock. Johnson et al. (2007) supported this claim as they assessed numerous variables and found that lithology and topography correlated most strongly to the presence of rock glaciers in the Lemhi Range in Idaho. Others have indicated that regional climate, past or current, is the controlling factor. Owen and England (1998) found rock glaciers only above 4000 m asl and in regions that received less than 1000 mm of precipitation in India and Pakistan. These conditions allow for the maintenance of permafrost, which is well noted to be important for the presence of rock glaciers (Haeberli et al., 2006; Kääb et al., 1997; Lugon and Stoffel, 2010).

Although there is still much controversy surrounding rock glacier terms, classifications, and origins (Berthling, 2011; Hamilton and Whalley, 1995; Martin and Whalley, 1987; Shroder et al., 2000; Vitek and Giordino, 1987), it is commonly accepted that Wahrhaftig and Cox (1959) contributed much to our current knowledge of rock glaciers and served as a springboard to subsequent studies that both advanced and supported their results (Barsch, 1992, 1996; Haeberli, 1985, 1990; Vitek and Giardino, 1987) or added to the claims made (Clark et al., 1994; Dobhal, 2008; Potter, 1972; Shroder et al., 2000; Whalley, 1974).

Terms and descriptions of different forms of rock glaciers were first put forth or popularized by Wahrhaftig and Cox (1959). They classified rock glaciers by their shape: lobate rock glaciers, which are wider than they are long; tongue-shaped, which are longer than they are wide; and spatulate, which broaden at the front of the rock glacier. The publication of their article actually resulted in confusion of rock glacier terminology as interest in rock glaciers increased and subsequent publications used different terms for similar or identical features and processes (e.g. Hamilton and Whalley, 1995; Outcalt and Benedict, 1965). Subsequently, several papers have been published in an attempt to unify or clarify rock glacier nomenclature (Berthling, 2011; Hamilton and Whalley, 1995).

2 Rock glaciers as agents of erosion

Rock glaciers serve as significant conveyors of material in mountain environments and greatly influence the landscape (Humlum, 2000; Owen and England, 1998). Surprisingly, relatively little research has been conducted on the erosional influence of rock glaciers, even though they pose a significant force to alpine areas (Humlum, 2000). Wahrhaftig and Cox (1959) calculated headwall erosion rates based on mass of rock glaciers, and a few subsequent studies have since investigated the erosional influence of rock glaciers (Barsch, 1977, 1996; Höllermann, 1983; Humlum, 2000). Movement of rock glaciers provides information on the amount of sediment they transport. Wahrhaftig and Cox (1959) recorded some of the most extensive rates of rock glacier movement of that time period. They made these measurements with the use of aerial photographs and by recording the distance between the headwall of rock glaciers and boulders. Capps (1910) had listed observations that supported the idea that rock glaciers move, but none had reported specific measurements on rock glacier rates. Techniques of measuring rock glacier movement are still being developed and evaluated (Kääb et al., 1997; Monnier et al., 2011; Wright, 1961).

3 Climate and rock glaciers

Wahrhaftig and Cox (1959) assessed rock glaciers for potential relationships with worldwide climate events. They estimated rock glacier formation and advance and retreat in regard to climate changes and topographic limitations. Their assessment revealed a trend in climate fluctuations stretching back to thousands of years bce. Only more recently have rock glaciers been evaluated in reference to global climate change (e.g. Berger et al., 2004; Millar et al., 2012; Ribolini et al., 2010), and the relationship between rock glaciers and climate is still debated. Some studies have found that climate directly influences rock glaciers. Lugon and Stoffel (2010) found that the Ritigraben rock glacier in the Alps increased its rate of movement about 70% in warmer temperatures. Kääb et al. (1997) found indications that rock glaciers experienced changes in their vertical surface and horizontal movement in relation to changes in ice glacier mass balance. Increasing movement may result in a greater amount of material at the tongue of the glacier (Lugon and Stoffel, 2010). However, others have noted that rock glacier dynamics do not directly respond to temperatures because of the insulating influence of a blanket of debris (Brenning, 2005; Clark et al., 1994) and internal air movement (Juliussen and Humlum, 2008; Leopold et al., 2011). These factors may be especially evident in conditions of rapid climate change. Millar et al. (2012) found that rock glaciers buffer air temperatures, and that rock glacier temperatures lag behind air temperatures. This condition could enhance the importance of rock glaciers as a source of water and habitat in high-elevation areas (Millar et al., 2012; Schrott, 1996).

In either case, it is well acknowledged that climate and rock glaciers, at least to some extent, are intricately related, and Wahrhaftig and Cox (1959) were the first to note this relationship. The interest in rock glaciers and global climate change is quite fitting in retrospect of Wahrhaftig’s lifestyle and opposition to the use of fossil fuels (Christiansen et al., 2005). Wahrhaftig was a strong proponent of the use of public transportation and resisted automobiles and airplanes. He preferred traveling by boat to Alaska from California for fieldwork and continued to use pack animals for field excursions for as long as the USGS would allow. He displayed a lifestyle of genuine concern for the natural environment and later in his career became directly involved in environmental issues.

IV Conclusion

‘Rock glaciers of the Alaska Range’ heralded the modern study of rock glaciers and resulted in worldwide interest. Although papers on rock glaciers had been published before 1959, none described them in such detail or provided quantitative evidence of their form and processes. The thorough and in-depth study performed by Wahrhaftig and Cox laid the groundwork for rock glacier classification, erosional processes, origins, movement rates, microtopography, and relation to climate for decades to follow. The understanding of rock glaciers and their dynamics is still evolving, but Wahrhaftig and Cox (1959) established a firm foundation for the modern study of these high-elevation features. Interest in rock glaciers will probably continue to grow, especially in regard to global climate change and the complex dynamics of rock glacier processes.

Footnotes

Acknowledgements

The image of Clyde Wahrhaftig was used with permission from the University of California, Berkeley. Thanks to David R. Butler, an anonymous reviewer, Elyse Zavar, Clayton Whitesides, and Stephen Tsikalas for helpful comments on an earlier draft of this paper.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

References

Ballantyne

Harris

(1994) The Periglaciation of Great Britain. Cambridge: Cambridge University Press.

Barsch

(1977) Nature and importance of mass-wasting by rock glaciers in alpine permafrost environments. Earth Surface Processes 2(2–3): 231–245.

Barsch

(1992) Permafrost creep and rock glaciers. Permafrost and Periglacial Processes 3(3): 175–188.

Barsch

(1996) Rock Glaciers: Indicators for the Present and Former Geoecology in High Mountain Environments. Berlin: Springer.

Berger

Krainer

Mostler

(2004) Dynamics of an active rock glacier (Otztal Alps, Austria). Quaternary Research 62(3): 233–242.

Berthling

(2011) Beyond confusion: Rock glaciers as cryo-conditioned landforms. Geomorphology 131(3–4): 98–106.

Berthling

Etzelmüller

Eiken

. (1998) Rock glaciers on Prins Karls Forland, Svalbard. I: Internal structure, flow velocity and morphology. Permafrost and Periglacial Processes 9(2): 135–145.

Blagbrou

Farkas

(1968) Rock glaciers in San Mateo Mountains south-central Mexico. American Journal of Science 266(9): 812–823.

Brazier

Kirkbride

Owens

(1998) The relationship between climate and rock glacier distribution in the Ben Ohau Range, New Zealand. Geografiska Annaler: Series A, Physical Geography 80(3–4): 193–207.

10.

Brenning

(2005) Geomorphological, hydrological and climatic significance of rock glaciers in the Andes of Central Chile (33–35°S). Permafrost and Periglacial Processes 6(3): 231–240.

11.

Brown

(1925) A probable fossil glacier. The Journal of Geology 33(4): 464–466.

12.

Burger

Degenhardt

Jr Giardino

(1999) Engineering geomorphology of rock glaciers. Geomorphology 31(1): 93–132.

13.

Butler

(2012) The impact of climate change on patterns of zoogeomorphological influence: Examples from the Rocky Mountains of the Western USA. Geomorphology 157–158 (July): 183–191.

14.

Capps

(1910) Rock glaciers in Alaska. Journal of Geology 18: 359–375.

15.

Chiax

(1923) Les coulees de blocs du Pare National Suisse d’Engadine (note preliminaire). Le Globe (Organe de la Societe de Geographic de Geneve) 62(4): 1–34.

16.

Christensen

Curtis

Sloan

(2005) Clyde Wahrhaftig. Available at: http://eps.berkeley.edu/alumni/wahrhaftig.php.

17.

Clark

Gillespie

(1994) Debris covered glaciers in the Sierra Nevada, California, and their implications for snowline reconstructions. Quaternary Research 41(2): 139–153.

18.

Clark

Steig

Potter

Jr . (1996) Old ice in rock glaciers may provide long-term climatic records. EOS, Transactions of the American Geophysical Union 217(23): 221–222.

19.

Cross

Howe

(1905) Geography and general geology of the quadrangle. In: Silverton Folio, U.S. Geological Survey Geologic Folio no. 120, 1–25.

20.

Dobhal

(2008) Snout retreat and mass balance of debris covered glacier-Chorabari, Garhwal Himalaya, India. Abstract presented at the International Workshop on Cryosphere and Hazards for the Hindu Kush, Himalaya and Tibetan Plateau, 31 March–2 April, Kathmandu, Nepal.

21.

Evin

(1993) Glacier et glacier rocheux dans les vallons de Mongioie et de Schiantala. Une nouvelle interprétation. Zeitschrift für Gletscherkunde und Glazialgeologie 27(28): 1–10.

22.

Giardino

Vitek

(1988) The significance of rock glaciers in the glacial–periglacial landscape continuum. Journal of Quaternary Science 3(1): 97–103.

23.

Haeberli

(1985) Creep of mountain permafrost: Internal structure and flow of alpine rock glaciers. Mitteilungen der Versuchsanstalt fur Wasserbau, Hydrologie und Glaziologie 77, Zurich, 142 pp.

24.

Haeberli

(1990) Drilling operation and core recovery. In: Haeberli

(ed.) Pilot Analyses of Permafrost Cores from the Active Rock Glacier Murtel, Piz Corvatsch, Eastern Swiss Alps. A Workshop Report, Arbeitsheft VAW/ETHZ 9, 4–7.

25.

Haeberli

Hallet

Arenson

. (2006) Permafrost creep and rock glacier dynamics. Permafrost and Periglacial Processes 17(3): 189–214.

26.

Hafner

(1994) Pikas and permafrost: Post-Wisconsin historical zoogeography of Ochotona in the Southern Rocky Mountains, USA. Arctic, Antarctic, and Alpine Research 26(4): 375–382.

27.

Hamilton

Whalley

(1995) Rock glacier nomenclature: A re-assessment. Geomorphology 14(1): 73–80.

28.

Hauck

Kneisel

(eds) (2008) Applied Geophysics in Periglacial Environments. Cambridge: Cambridge University Press.

29.

Höllerman

(1983) Blockgletscher als Mesoformen der Periglaziastufe – Studien aus Europaischen und Nordamerikanischen Hochgebirgen. Bonner Geografische Abhandlungen 67. Bonn: Dummlers Verlag.

30.

Hollingworth

(1934) Some solifluction phenomena in the northern part of the Lake District. Proceedings of the Geologists’ Association 45(2): 167–188.

31.

Howe

(1909) Landslides in the San Juan Mountains, Colorado. US Geological Survey Professional Paper 67.

32.

Humlum

(2000) The geomorphic significance of rock glaciers: Estimates of rock glacier debris volumes and headwall recession rates in West Greenland. Geomorphology 35(1): 41–67.

33.

Johnson

Thackray

Van Kirk

(2007) The effect of topography, latitude, and lithology on rock glacier distribution in the Lemhi Range, central Idaho, USA. Geomorphology 91(1): 38–50.

34.

Juliussen

Humlum

(2008) Thermal regime of openwork block fields on the mountains Elgåhogna and Sølen, central-eastern Norway. Permafrost and Periglacial Processes 19(1): 1–18.

35.

Kääb

Haeberli

Gudmundsson

(1997) Analysing (Sic) the creep of mountain permafrost using high precision aerial photogrammetry: 25 years of monitoring Gruben Rock Glacier, Swiss Alps. Permafrost and Periglacial Processes 8(4): 409–426.

36.

Karlén

(1973) Holocene glacier and climate variations, Kebnekaise Mountains, Swedish Lapland. Geografiska Annaler Series A, Physical Geography 55(1): 26–63.

37.

Krauskopf

(no date) Biographical memoirs: Allan V. Cox. Available at: http://www.nap.edu/html/biomems/acox.html.

38.

Leopold

Williams

Caine

. (2011) Internal structure of the Green lake 5 rock glacier, Colorado Front Range, USA. Permafrost and Periglacial Processes 22(2): 107–119.

39.

Lugon

Stoffel

(2010) Rock-glacier dynamics and magnitude–frequency relations of debris flows in a high-elevation watershed: Ritigraben, Swiss Alps. Global and Planetary Change 73(3): 202–210.

40.

Martin

Whalley

(1987) Rock glaciers. 1. Rock glacier morphology – classification and distribution. Progress in Physical Geography 11(2): 260–282.

41.

Millar

Westfall

(2010) Distribution and climatic relationships of the American pika (Ochotona princeps) in the Sierra Nevada and western Great Basin, USA: periglacial landforms as refugia in warming climates. Arctic, Antarctic, and Alpine Research 42(1): 76–88.

42.

Millar

Westfall

Delany

(2012) Thermal and hydrologic attributes of rock glaciers and periglacial talus landforms: Sierra Nevada, California, USA. Quaternary International. doi: org/10.1016/j.quaint.2012.07.019.

43.

Monnier

Camerlynck

Rejiba

. (2011) Structure and genesis of the Thabor rock glacier (northern French Alps) determined from morphological and ground-penetrating radar surveys. Geomorphology 134(3): 269–279.

44.

Outcalt

Benedict

(1965) Photo-interpretation of two types of rock glaciers in the 499 Colorado Front Range, USA. Journal of Glaciology 5: 849–856.

45.

Owen

England

(1998) Observations on rock glaciers in the Himalayas and Karakoram Mountains of northern Pakistan and India. Geomorphology 26(1): 199–213.

46.

Potter

Jr (1972) Ice-cored rock glacier, Galena Creek, northern Absaroka Mountains, Wyoming. Geological Society of America Bulletin 83(1): 3025–3057.

47.

Ribolini

Chelli

Guglielmin

. (2007) Relationships between glacier and rock glacier in the Maritime Alps, Schiantala Valley, Italy. Quaternary Research 68(3): 353–363.

48.

Ribolini

Guglielmin

Fabre

. (2010) The internal structure of rock glaciers and recently deglaciated slopes as revealed by geoelectrical tomography: Insights on permafrost and recent glacial evolution in the Central and Western Alps (Italy–France). Quaternary Science Reviews 29(3): 507–521.

49.

Roer

Haeberli

Avian

. (2008) Observations and considerations on destabilizing active rock glaciers in the European Alps. Ninth International Conference on Permafrost 2: 1505–1510.

50.

Schrott

(1996) Some geomorphological-hydrological aspects of rock glaciers in the Andes, San Juan, Argentina. Zeitschrift für Geomorphologie, Supplement 104: 161–173.

51.

Shroder

Bishop

Copland

. (2000) Debris-covered glaciers and rock glaciers in the Nanga Parbat Himalaya, Pakistan. Geografiska Annaler Series A, Physical Geography 82(1): 17–31.

52.

Spencer

(1900) A peculiar form of talus. Science 11: 188.

53.

Squyres

Carr

(1986) Geomorphic evidence for the distribution of ground ice on Mars. Science 231(4735): 249–252.

54.

Tyrrell

(1910) ‘Rock glaciers’ or chrystocrenes. Journal of Geology 28: 549–553.

55.

Vitek

Giardino

(1987) Rock glaciers: A review of the knowledge base. In: Giardino

Shroder

Jr Vitek

(eds) Rock Glaciers. London: Allen and Unwin, 106–125.

56.

Whalley

(1974) Rock glaciers and their formation as part of a glacier debris-transport system. Geographical Papers 24, University of Reading, 48 pp.

57.

Wei-Dong

Smith

(2005) Dramatic decline of the threatened Ili pika Ochotona iliensis (Lagomorpha: Ochotonidae) in Xinjiang, China. Oryx 39(1): 30–34.

58.

Willers

O’Hara

. (2012) A categorical, improper probability method for combining NDVI and LiDAR elevation information for potential cotton precision agricultural applications. Computers and Electronics in Agriculture 82: 15–22.

59.

Wright

(1961) Late Pleistocene climate of Europe – a review. Geological Society of America Bulletin 72(6): 933–998.

Clyde Wahrhaftig and Allan Cox (1959) Rock glaciers in the Alaska Range. Bulletin of the Geological Society of America 70(4): 383–436

Abstract

Keywords

I Rock glaciers

II The influence of Wahrhaftig and Cox (1959)

III The contribution of Wahrhaftig and Cox (1959)

1 Origins and classifications of rock glaciers

2 Rock glaciers as agents of erosion

3 Climate and rock glaciers

IV Conclusion

Footnotes

Acknowledgements

Funding

References