Geographical Cycle” at the Turn of the 1960S

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TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S

DUAS REAVALIAÇÕES DO “CICLO GEOGRÁFICO” DE DAVIS NA VIRADA DA DÉCADA DE 1960

DEUX RÉÉVALUATIONS DU «CYCLE GÉOGRAPHIQUE» DE DAVIS AU TOURNANT DES ANNÉES 1960

CHRISTIAN GIUSTI1

1 Faculté des Lettres, Sorbonne Université, Paris. Laboratoire de Géographie Physique, UMR 8591 CNRS, Meudon. E-mail: [email protected] ORCID: https://ORCID.0000-0002-6531-3572

Received 15/11/2020 Sent for correction: 30/11/2020 Accepted: 15/12/2020

To Marie-Hélène Auclair, Librarian in Sorbonne (1975-1985), a most helpful friend during my early years of research.

ABSTRACT Many geomorphologists today refer to Davis and his ideas without really knowing what that implies. In the second half of the 20th century, two re-evaluations of the Davisian system were carried out, which the renewed popularity of the “peneplain” concept has led us to bring back to light and discuss. Key words: Davis, geographical cycle, peneplain, Chorley, Klein.

RESUMO Muitos geomorfólogos hoje se referem a Davis e suas ideias sem realmente saber o que isso implica. Na segunda metade do século XX, foram realizadas duas reavaliações do sistema Davisiano, cuja renovada popularidade do conceito de “peneplanície” nos levou a trazer de volta à luz e discutir. Palavras-chave: Davis, ciclo geográfico, peneplanície, Chorley, Klein.

RÉSUMÉ De nombreux géomorphologues font aujourd'hui référence à Davis et à ses idées sans vraiment savoir ce que cela implique. Dans la seconde moitié du XXe siècle, deux réévaluations du système davisien ont été effectuées, que la popularité renouvelée du concept de «pénéplaine» nous a amenées à remettre en lumière et à discuter. Mots clés: Davis, cycle géographique, pénéplaine, Chorley, Klein.

« Le sentiment joue son rôle même dans la science ». E. de Martonne (1929, 419).

The publication of the seminal hydrophysical paper by Robert E. Horton [1875-1945] in March 1945 is regarded as the starting point of the quantitative fluvial revolution in the aftermath of World War II (KENNEDY, 1978; 1992; STRAHLER, 1992; CHORLEY, 1995; KENNEDY, 2006, p. 98-111). Richard J. Chorley [1927-2002], commenting on Horton (1945) fifty years later, stated that “Horton’s article ushered in a period of engineering geomorphology that still lasts” (CHORLEY, 1995, p. 533). In France, the active promoters of a quantitative approach in geomorphology were mainly a geologist, André Cailleux [1907- 1986], and a geographer, Jean Tricart [1920-2003], both involved in the construction of a breakthrough structural and climatic geomorphology, fully opposed to the physiographic timebound approach developed by William M. Davis [1850-1934] and his followers, among whom Henri Baulig [1877-1962] may by far be considered as the most influential (BECKINSALE; CHORLEY, 1991, p. 256-283). GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S

Arthur N. Strahler [1918-2002] gave a detailed account of the period 1945-1960 in Columbia, years during which quantitative dynamic geomorphology developed, before being widely distributed (STRAHLER, 1992; KENNEDY, 2006; CHORLEY, 2008, p. 925-960). A totally whiggish view of history would consist in contrasting the old qualitative geomorphology, embodied by Davis’s obsolescent ideas, with the young quantitative geomorphology embodied by Strahler and his tutee followers, the bearer of all promises and the future of geomorphology1. No one envisages of contesting that a change of scales and methods accompanying a paradigm shift occurred in the middle of the last century. But both Strahler and his American pupils – notably Stanley. A. Schumm [1927-2011] and Mark A. 22 Melton [1930-2019] – never stopped working on all sort of rivers, the main feature of the cyclic mode of evolution. One can cite the fundamental article on time, space and causality (SCHUMM; LICHTY, 1965), as well as the synthesis on the fluvial system (SCHUMM, 1977). In this now classic book, the first chapter illustrates that the scientific project was to put “the idealized fluvial system” to the test against the reality (SCHUMM, 1977, p. 3)2, i.e., observation and experience facts (the same manner Davis had constructed an “idealized cycle” and multiplied block diagrams). Based on a cross-analysis of Hutton, Lyell, Darwin, Dana, Gilbert and Horton, Barbara A. Kennedy [1943-2014] insisted on “the impossibility of making simple divorce between the dynamic (or physical) approach and the historical”, adding that “if we simply consider a sequence of events of all, physically-possible shapes and sizes, then both equilibria and cataclysms may be accommodated as potential occurrences” (KENNEDY, 1992)3. To which it will be added that the Davisian geomorphology is also a dynamic geomorphology in its own way, centred on the dynamism of landforms, not on that of processes (KLEIN, 1993). As M. Morisawa (1985) clearly stated, “the real legacies of the hydrophysical approach were the rapid demise of the Davisian system and also the tendency of much geomorphology in the second half of the century to concentrate on the smaller scales of space and time and on the effects of measurable processes” (in CHORLEY, 1995, p. 552). The issue of the quantitative revolution in geomorphology, well documented (e.g., KEYLOCK, 2003; KENNEDY, 1996. BURT et al., 2008), therefore does not seem to ask for further development. Actually, this essay is rather an attempt to compare two re-evaluations of the Davisian system. The first one occurred at the end of the 1950s, namely the acyclic theory of Claude Klein [1924-2005], which went largely unnoticed outside the French-speaking sphere (KLEIN, 1959a,b; 1960). The second one was initiated by Richard J. Chorley in the early 1960s, first as a lecture given at Madingley Hall4 in 1963, which proved strongly influential (CHORLEY, 1965), later extended through an authoritative biography of Davis (CHORLEY;

1 A variation would be to assert that Gilbert had built a sound foundation for the study of landforms and processes, but because of Davis, it was not until 1945 that the true scientific method would have been again put to work. 2 On the other hand, the ‘physical’ approach is favored in Fluvial Processes in Geomorphology, although peneplains and pediments appear in the end (LEOPOLD et al., 1964), and also in River variability and complexity (SCHUMM, 2005). 3 See the long-time misunderstood work of J H. Bretz on the Channeled Scablands (1923; 1928; BRETZ; SMITH; NEFF, 1956), as well as the synthesis by D. M. Burr, P. A. Carling and V. M. Baker (2009). 4 “Madingley Hall” is the conference center for the University of Cambridge. See: https://en.wikipedia.org/wiki/Madingley (accessed January 2021, 4th).

BECKINSALE; DUNN, 1973). After having call up both re-readings of the “geographical cycle5”, the Davisian system will be put in perspective.

1. KLEIN’S ACYCLIC THEORY AND THE LIMITS OF THE CYCLIC THEORY (1959-60)6

The noteworthy English translation of “Die morphologische Analyse” (PENCK, 1924) a few years after the end of World War II by Hella Czech and Katherine C. Boswell (PENCK, 1953)7 has enabled many non-German-speaking readers to discover the thought of Walther Penck freed from the Davisian prism of interpretation (TUAN, 1958; SIMONS, 1962; 23 GIUSTI, 2012b). In France, opinions are divided. On one side, Henri Baulig defends until his last breath Davisian geomorphology (BAULIG, 1950; 1951; 1952 a,b,1956a), while carefully echoing the American quantitative studies (BAULIG, 1950, p. 64-68 on KESSELI; MACKIN; 1959 on STRAHLER; SCHUMM; MELTON)8. On the opposite side, Jean Tricart develops a fierce opposition to Davis and lead most French geomorphologists towards climatic morphology (MARTONNE, 1913; 1940; 1946; CHOLLEY, 1950; TRICART, 1965), which he enlarges and deepens after his pioneering thesis on the Eastern Paris Basin (TRICART, 1949-1952, TRICART; CAILLEUX, 1962-1974). The position of Pierre Birot [1909-1984] is much more elaborated, defending a middle line between Davis and Penck (BIROT, 1958). As a student at the ‘École normale supérieure de Saint-Cloud’, Claude Klein had the opportunity to hear Birot’s lessons in the late 1940s. And a few years later, when Klein exposes his views on acyclism at the end of the 1950s, his conceptual geomorphological toolbox includes Cholley’s polygenism9, Baulig’s eustatic polycyclism, Erhart’s biorhexistasis theory10, Quaternary evolution of the Eastern Paris Basin (TRICART, 1952), plus Davis read with Baulig’s perceptive commentaries, and Walther Penck read through the antithetic prism of Baulig (negative) and Birot (positive). For twenty years or so (1953-1973), Claude Klein studied the geology and geomorphology of a large area at the contact with the Armorican Massif and the Paris Basin (GUILCHER, 1974). A hefty thesis was soon published under the form of two impressive volumes (KLEIN, 1975), though the principles of the acyclic theory were fully defined from 1959-1960: “Surfaces polygéniques et surfaces polycycliques” (KLEIN, 1959a), “Surfaces de regradation et surfaces d’aggradation” (KLEIN, 1959b), and “La notion de rythme en

5 This expression is hardly ever used, most often replaced by “cycle of erosion” or more rarely (Baulig, after Lawson) by “geomorphic cycle”. An essential part of Davis’s scientific message is thus obscured: the spatial expression of landforms in the landscape. Because Carl O. Sauer [1889-1975] was clearly aware of this attribute, he reacted vigorously by reminding American geographers that a landscape cannot be reduced to its only (geo)morphological features, to the exclusion of its other attributes: natural and cultural (Sauer, 1925). What UNESCO and the World Heritage Center have accomplished since 1972 is worldwide known: https://whc.unesco.org/en/conventiontext/ (accessed January 2021, 4th). 6 It seemed better not to translate into English the quotes in French language (author’s italics, unless otherwise indicated). 7 Not surprisingly, the Geographical Essays (DAVIS, 1909) were immediately reprinted by Dover in 1954. 8 As well as a specific tribute to Grove K. Gilbert (BAULIG, 1958): see C. Giusti (2019). 9 The main papers of André Cholley [1889-1975] are collected in Recherches morphologiques (CHOLLEY, 1957). 10 Henri Erhart [1898-1982] is a soil scientist who originated the theory of biorhexistasis (ERHART, 1956).

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S morphologie” (KLEIN, 1960)11. It would be irrelevant here to go into the details of the geological grounds of the acyclic theory (GUILCHER, 1974; KLEIN, 1990). However, it seems necessary to indicate how Klein’s acyclism is actually a re-evaluation of Davis’s cycle theory, and at the same time the formulation of the morphogenetic consequences of a mode of evolution comparable to the “steady state” simultaneously defined in the Appalachians on the other side of the Atlantic (HACK, 1960)12. It was the study of the Limousin at large and other old lands13 of western and central Europe that would later lead Klein to modulate both in space and in time the respective share of the cyclic, polycyclic and acyclic modes of evolution (KLEIN, 1990; 1993; 1997). With the eustatic planation and the polycyclic mode of 24 evolution, Baulig (1928) had extended the scope of the “geographical cycle” by the demonstration that “des cycles successifs quant à leur origine, peuvent être simultanés quant à leur développement” (ibid., 46-47). Klein decides to explore another domain, the case of surfaces plane from birth (e.g., a surface of marine regression), that are known to remain plane for millions of years14 due to the never-ending interplay of successive regradations or aggradations resulting in a large acyclic surface (KLEIN, 1959b)15. And that explains the choice of such a vast field of investigation, unceasingly studied from 1953 to 1973. In order to demonstrate the validity of the acyclic theory, “il était indispensable … d’aller de l’extrême ouest du Massif Armoricain jusqu’au-delà du centre du Bassin de Paris et au Limousin inclus. Initialement, Klein pensait examiner aussi le contact du massif du Sud-Ouest britannique avec le Mésozoïque, jusqu’aux Mendips au nord ; mais il y a renoncé assez rapidement” (GUILCHER, 1974)16. Klein’s relationship to Davis’s ideas was mainly built on a careful reading of Henri Baulig17. During the 1950s, “le plus brillant disciple français de W. M. Davis” (KLEIN, 1999) published two thorough papers about the surfaces of planation (BAULIG, 1952b, 1956a). He also sifted through his erudition the new ideas in quantitative analysis, Birot’s “Methods” (BAULIG, 1957) and texts by Arthur N. Strahler, Stanley A. Schumm and Mark A. Melton (BAULIG, 1959). As a discussion of Klein’s contribution to the cyclic, bicyclic and polycyclic modes of evolution would be outside the scope of this article on the “geographical

11 At the time, no journal in France was capable of publishing in a single article the ideas set out in these three publications, which are in fact the three parts of a single essay on acyclism. Even de Martonne, Baulig or Birot were obliged to divide their main theoretical works into two separate issues. 12 John T. Hack [1913-1991] was an American geologist and geomorphologist known for his contributions to establish the dynamic equilibrium concept in landscapes. Hack was a student of Kirk Bryan, graduated from Harvard University, where he received his bachelor’s and master’s degrees and doctorate in geomorphology. 13 Besides Limousin, two other regions of the Massif Central: the ‘Monts du Vivarais’ and the Rhone Piedmont, the ‘Monts de Lacaune’ and the ‘Montagne Noire’ (GIUSTI, 2002; 2016). In addition to the Massif Armoricain: the Vendée Bocage, the Normandy-Maine dome, Dartmoor and Bodmin Moor in the south-west of England. At the front of the Alps: the Vosges, the Fichtelgebirge, the Böhmerwald, the Bayerischer Wald, and the Danubian piedmont (KLEIN, 1997). 14 From the end of the Jurassic to the end of the Oligocene, roughly 130 million years (KLEIN, 1975). 15 In the same way and for the same reasons than A. Guilcher (1952), for whom an article by Henri Baulig cannot be summarized, I can share with the reader only the essential ideas, inviting to read Klein's original papers for further notice. 16 « C’est précisément entre Exeter et Torquay que l’intérêt véritable de l’étude couplée d’un massif ancien et de ses bordures sédimentaires nous est apparu, en 1953 » (KLEIN, 1990, p. 65). 17 On the life and work of Henri Baulig, see E. Juillard (1975) and C. Klein (1977), as well as Chapter 8 by R.P. Beckinsale and R.J. Chorley (1991) and the dissertation in French by C. Klein (1999).

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S cycle”, we will focus on the acyclic mode of evolution as Klein conceived it during his thesis years18. In the 1950s, the flattening of landforms still remains a major concern, a theme Klein contribute to enrich with new concepts from an idea that had never really been explored, although foreseen from a Davisian perspective by H. Baulig (1926; 1928) and N. Fenneman (1936), later by P. Birot (1958) as an extension of the Primärrumpfe approach followed by Penck (1924).

(a) In his paper on the landforms of Upper Belgium, H. Baulig (1926, p. 22419) notes that from the Triassic to the end of the Oligocene, “les transgressions se sont étalées 25 paisiblement sur des surfaces à peu près complètement nivelées”, and that nothing “ni dans la nature des dépôts, ni dans leur mode de gisement, n’indique que la région ait jamais possédé un relief marqué: les déformations ont donc été assez graduelles pour ne pas déterminer d’érosion vigoureuse dans la masse soulevée”. In his study of the Limousin plateaus, H. Baulig (1928, p. 89) observes in the same way that in certain sectors, the “plaine d’érosion éogène” (the “Eogene Surface”) intersect the « surface post-hercynienne … sous un angle si faible que les deux surfaces sont pratiquement confondues” (my italics). A more precise scenario is set out a few lines later in a passage Klein most likely meditated upon: “la surface d’érosion subaérienne – pré- permienne ou pré-triasique selon les points – était couverte d’une épaisse couche de décomposition quand la transgression liasique vint la décaper, puis la fossiliser ; la même surface fut retrouvée plus tard toujours au voisinage du niveau de base par l’érosion tertiaire, qui l’exhuma une seconde fois pour la recouvrir ensuite d’un manteau résiduel tout à fait semblable à celui de l’époque permo-triasique. Dans cette région, exceptionnellement stable, la surface éogène se confond pratiquement avec la surface post-hercynienne” (my italics). (b) The idea that erosion could act in a framework other than that of the geographical cycle was put forward during the 1930s by Neville M. Fenneman [1865-1945]20 in a paper known of Klein (1975). In December 1935, Fenneman (1936) delivered as past president of the Geological Society of America a speech in which he discussed the cyclic and non-cyclic aspects of erosion. Davis had just passed, and Johnson’s book (1931) on the Appalachians, a model of denudation chronology, was on everyone’s mind. After evoking the question of the “multiplicity of surfaces (topographic or mathematical, actual or conceptual) at different levels”, a main topic in the history of cycle theory, Fenneman quotes “another factor recognized though not yet prominent in discussions, which may produce surfaces at an indefinite number of levels… the slow wasting of a surface without change of characteristic form” (FENNEMAN, 1936, p. 92, my italics). In order to characterize this type of situation, Fenneman proposes to employ the expression “non-cyclic”, an idea that he presented in March 1933 to the members of the Chicago Geological Society and tested the same year in an essay on the Alleghany Plateau. To illustrate his idea, Fenneman uses a metaphor: « Cycles have parts, and the parts make wholes, and the wholes may be counted like apples. Non-cyclic erosion can only be measured like cider. There is neither part nor whole but only much or little. The exact altitude of a surface affected by such erosion does

18 See C. Klein (1993; 1997) for further developments. 19 See also C. Klein (1985, p. 102; 1999, p. 67, note 39-b). 20 J.L. Rich (1945), Memorial to Nevin M. Fenneman.

not record an event, but only a continuing process which may be fast or slow » (ibid., my italics). (c) Baulig (1952b, p. 175-176) devoted only a few lines to this essay, mentioned in the section on “pseudo-peneplains” in connection with the Gipfelflur and the Denudationsniveau theory21. “Acyclic” makes its appearance in the French language as an adjective under the modernist pen of J. Beaujeu-Garnier (1954, p. 301) who, in her “Essai de morphologie limousine”, intends thereby to distance herself from the polycyclic views of A. Demangeon (1910) and H. Baulig (1928)22. While M.-A. Lefèvre23 criticizes the word, Baulig (1955, p. 78) observes that “le terme ‘acyclique’ a été employé paradoxalement à propos d’une région (le Limousin Central…) résultant d’une évolution longue, complexe, où il est impossible de faire la part des 26 cycles qui se sont peut-être succédé”. Baulig (1955) considers that acyclic “pourrait être conservé avec ce sens”, but in the end the word was not retained in the printed edition of the “Vocabulaire franco-anglo-allemand de géomorphologie” (BAULIG, 1956b). The notion receives a more original treatment from P. Birot (1958, p. 155- 161), who links it to “la théorie générale de la Primärrumpf developed especially by W. Penck” (ibid., p. 158). According to Birot, “la genèse des formes structurales peut être reconstituée dans le cadre de trois types d’évolution cyclique”, the acyclic mode being only an intermediate case between the monocyclic and bicyclic modes of evolution: thus, underpinned Birot, “le début des mouvements orogéniques serait assez lent pour ne donner lieu à aucun relief marqué, l’usure des versants se faisant à une vitesse équivalente. Il en résulterait une situation peu différente de la surface cyclique initiale prévue dans la théorie bicyclique” (ibid.). This position is no surprise given the tradition of the “French polycyclism” (Demangeon in Limousin, Briquet in the Cevennes, Musset in Western France, Baulig in the Ardennes and through the Central Plateau)24; but it is unparalleled and quite unique in its openness to the ideas of Walther Penck (GIUSTI, 2012b).

If the word “acyclic” is absent from Baulig’s Vocabulary, it is however well specified that “les surfaces d’érosion étendues sont souvent composites, polygéniques, comprenant deux ou plusieurs surfaces qui, développées successivement et déformées, se recoupent”: the expression “surface à facettes25” applies to this situation (BAULIG, 1956b). And it is for this situation that Klein intends to reserve the use of the word “polygenetic” (polygénique): pour “des éléments de surface qui se développent en continuité topographique au voisinage des dépôts de couverture qui les avaient lentement et successivement soustraits aux agents de l’érosion” (KLEIN, 1959a, p. 68). In Klein’s mind, it is clear that only “cette surface de fossilisation est une surface polygénique authentique”, considering that “ses éléments en ont été successivement fossilisés, et que, masqués sous des dépôts d’époques différentes, ils ont

21 On this question, see C. Giusti (2012b, p. 107-120). 22 On this point, see C. Klein (1975, p. 458), note (633). 23 See: https://www.bestor.be/wiki/index.php/Lefèvre,_Marguerite_(1894-1967) (accessed January 4th, 2021). 24 See R.P. Beckinsale and R.J. Chorley (1991, chapter 8), and C. Klein (1997). 25 See H. Baulig (1956b, § 164). – The concept of “faceted surface” was explored by H. Baulig (1926) in his paper on the landforms of Upper Belgium (also see BAULIG, 1952b, p. 170-171), and illustrated by C. Klein (1970, fig. 5, 200-201) in his paper on “surface de l’argile à silex” (clay-with-flints surface). – On the various meanings of the word “polygénique” or “polygenetic” see Davis (1890a, in 1909, p. 493), Chaput (1928), Baulig (1952b, p. 170-171; 1956b, § 164), Klein (1959a, p. 52-59), CILF (1979, p. 149), Goudie (2002, passim, especially BAUER, p. 430; BREMMER, p. 696; MIGOŃ, p. 788-792).

(a) According to Klein (1959b, p. 294-297), three groups of facts converge to explain the persistence of low-energy reliefs: the low loss of material in some massifs of Hercynian Europe during the Mesozoic and the Cenozoic, the low relative volume of sediments of detrital origin arriving in the sedimentary basin, and the numerous reworkings repeatedly affecting the same detrital materials (especially in the vicinity of the basement/basin limit). Morphological evolution occurs as a function of an original tectonic rhythm, which combines broad epeirogenic movements at slow speed, purely eustatic movements also at slow speed, and localized differential movements such as flexures or faults located along the main axes of the inherited tectonic network (ibid., p. 299). As for the resulting forms, if “le principe du Primärrumpfe […] explique convenablement la persistance des surfaces d’aplanissement du socle27, constamment regradées au cours de la mise en place de la couverture sédimentaire”, it is by no mean to accept the full of Penck’s theory28. The

26 In a private message, H. Baulig most welcomed C. Klein’s proposals on acyclism (KLEIN, 1999, p. 67, note 39-a). 27 The so-called “post-Hercynian surface” results from the flattening of the Variscan chain, and therefore deserves to be called a “surface of planation” in a strict way. Klein’s thesis (1975) is the study of how and why that true planation surface became and remain a large acyclic surface from the Jurassic to the end of the Oligocene, through the succession of regradation/aggradation surfaces of dynamic equilibrium. 28 The two papers by Klein (1984; 1985) on the centenary of the geographical cycle in geomorphology are a clear demonstration that their author read Penck with the glasses of Davis (1932) and Baulig (1939), and never felt the need of any change: see Giusti (2012b, p. 97-219) for further explanations.

question is less to ask “comment et quand une région donnée (du domaine étudié) est devenue une surface d’aplanissement” than to explain “pourquoi et pendant combien de temps elle est demeurée une surface de regradation” (KLEIN, 1959b, p. 300). (b) Klein (ibid., p. 301-302) describes minutely how “les surfaces de regradation et les surfaces d’aggradation sont par nature des surfaces d’équilibre mobile. […] En structure homogène, ce sont les vallées mûres29 et les interfluves aux larges convexités qui constituent l’essentiel des formes du modelé (de regradation). En structure lithologiquement contrastée, le développement des formes structurales se trouve limité : […] cuestas fossiles tertiaires du Sud du Bassin Parisien, lignes de relief appalachien dont la base s’est trouvée fossilisée par les faluns d’Anjou entre Segré et Châteaubriant”. A regradation surface is generally not a “plaine d’érosion” but rather 28 “une surface mollement vallonnée” consisting in “gently rolling swells alternating with shallow valleys” (i.e., a peneplain topography in the Davisian sense of the word). As for the surfaces of aggradation, they are made of accumulation, and so, “lorsqu’elles sont intactes, […] présentent ce haut degré de perfection qui est le privilège des surfaces construites”, e.g., the clay-with-flints surface (la “surface de l’argile à silex”: ibid., p. 302; also see KLEIN, 1970). It is important to notice, first that an aggradation surface is always genetically associated with a contiguous regradation surface, second that it is also possible for an aggradation surface to transform into a regradation surface. (c) The acyclic mode of evolution (KLEIN, 1959b, p. 303-306) is the consequence from the fact that “les équilibres morphologiques sont par nature des équilibres mobiles”. Due to this essential attribute, dynamic equilibria “témoignent d’une relative tolérance vis-à-vis des variations locales et instantanées des divers termes impliqués dans le système”, such an adaptability playing a key-role in the “variations systématiques de certains de ces termes à la condition que ces variations s’effectuent entre certaines limites”. Klein refers here to a threshold of morphological activity, beyond which the cyclic or polycyclic modes may prevail, below which “il n’est pas apparu de discontinuités dans les formes parce qu’il n’y a pas eu de discontinuité sensible dans le jeu des forces en présence”: hence the acyclic mode. Klein’s opinion is that “la reprise d’érosion en régime acyclique est un phénomène diffus, et la surface déformée n’est pas disséquée par l’incision brutale des artères du drainage. La perte de substance reste répartie sur l’ensemble de cette surface dont tous les points demeurent solidaires” (ibid., p. 304). It is because the conjugated tectonic, eustatic and bioclimatic rhythms were profoundly modified from the Miocene onwards that the surfaces of regradation and aggradation of Western France were largely dissected, reduced to the state of “dead” uplands (“Vorzeitformen”) when rivers started to dig valleys (ibid., p. 305).

Klein (1959b, p. 306-317) does not at all intend to plea against “le bien-fondé des conceptions classiques de la géomorphologie cyclique”, rather to examine “les zones d’ombre du raisonnement cyclique” in order to assign precise limits to the field of validity of the Davisian cycle theory. What the author disputes (ibid., p. 315-316), “c’est le fait qu’à l’extrême diversité des rythmes tectoniques (ou eustatiques) puisse ne correspondre qu’un seul mode d’expression morphologique : le mode cyclique”, hence the definition of an “évolution acyclique rythmée par des mouvements du sol à très grand rayon de courbure (ou par des mouvements eustatiques) d’amplitude modérée et à vitesse lente”, of which the

29 In the descriptive sense of a broad flared valley.

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S surfaces of regradation and aggradation are the characteristic landforms of an ever transient landscape. Klein’s paper (1960) about the rhythm in geomorphology allows him to enlarge discussion. After recalling that “le schéma davisien, inattaquable dans sa logique interne, n’en reste pas moins associé à un rythme tectonique bien défini, a rapid uplift of a land mass, followed by a prolonged stillstand” (ibid., p. 375), and that “le cycle d’érosion, tel que le concevait Davis, procède d’une vision statique du monde” (ibid., p. 379), Klein considers it necessary to pose “le problème des limites qu’il paraît nécessaire de reconnaître au schéma de Davis” (ibid., p. 382). For Klein (ibid., p. 383), “l’évolution géomorphologique est réglée par 29 la manière dont se conjuguent, suivant la ligne du temps, trois rythmes fondamentaux”, i.e., tectonic, eustatic and bioclimatic. While the first two define “l’importance du volume continental offert aux agents de l’érosion”, the last orders “la succession des systèmes d’érosion” (ibid.). Crisis may occur that the morphologist can neither ignore nor underestimate: for example, “la mise en place d’une chaîne de plissement tel l’édifice alpin” in the tectonic order, “la transgression cénomanienne […] sur les marges de certains massifs anciens” in the eustatic order, or the “glaciations quaternaires” in the bioclimatic order (ibid., p. 383-384). With the exception of these spatially and temporally localized “crises”, “il est bien établi que des manifestations tectoniques, eustatiques et bioclimatiques d’un style tout différent ont rythmé la vie des formes dans d’autres domaines et à d’autres époques” (ibid., p. 384). These “rythmes fondamentaux sont donc tantôt en conjonction de phase (leurs effets s’additionnent sur le plan morphogénétique)”, and this defines the framework for the cyclic and polycyclic modes of evolution, “tantôt en opposition de phase (leurs effets se neutralisent partiellement)”, and that defines the framework for the acyclic mode of evolution (ibid., p. 385). Between these opposite modes of evolution “existent tous les termes de passage […]. L’amplitude du déphasage peut être quelconque et la réunion des circonstances bioclimatiques les plus favorables à une attaque active des roches peut précéder ou suivre les effets distincts ou conjugués des mouvements tectoniques et des mouvements eustatiques” (ibid., p. 384-385). This point is essential because it shows that Klein’s geomorphological world is a contingent one30: if we rewind the film of the intermingled history of the Armorican Massif and its sedimentary covers back to the end of the Permian period, and then if we relaunch the action, the subsequent interplay of forces, factors and rhythms would produce new arrangements and combinations leading to a result totally different from the current world. This is the key-point on which Klein clearly separates from Davis (see the second part of this paper, inspired by R. Inkpen and P. Collier brilliant essay). In Klein’s opinion, “le système des forces et des résistances qui sont impliquées dans l’évolution de ces formes31 n’est pas un système clos, ni du côté des agents dynamiques internes, ni du côté des agents dynamiques externes” (KLEIN, 1960, p. 379). Within the Davisian framework of an idealized geographical cycle implying an undisturbed succession of ordered stages and not any accidents to intervene, everything is reduced to a nearly closed

30 Also see the final section (conclusion) of Klein’s thesis (1975, 739-750). 31 “Les formes du terrain” (Davis, Baulig…) as opposed to “les formes du modelé” (Tricart) (KLEIN, 1960, p. 379; and also 1993). On the notion of system in geomorphology, see R.J. Huggett (2007).

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S system (except the graded river) of interdependent variables. On the opposite, the acyclic mode of evolution is a totally open system with a seemingly infinite field of multifarious possibilities. During the Neogene period, the tectonic, eustatic and bioclimatic rhythms lead to the dissection of acyclic surfaces inherited from a previous long macro-sequence that began during the Jurassic and was completed in the very Early Miocene. During that acyclic macro- sequence, the variations of the intensity of the ratio between endogenetic and exogenetic forcing of landform development allow to define shorter acyclic subsequences, each with specific tectonic, eustatic, and bioclimatic rhythms, ensuing a succession of acyclic surfaces never entering the cyclic mode (KLEIN, 1975). We may say the sequence is to the acyclic 30 mode what the stage is to the geographical cycle, but the last involves determinism while the first supposes contingency.

2. CHORLEY’S RE-EVALUATION OF THE CLASSIC CYCLIC THEORY (1965)

Volume 500 of the Professional Papers of the United States Geological Survey, Theoretical papers in the hydrologic and geomorphic sciences, begins with two notably influential essays: the first by L.B. Leopold and W.B. Langbein (1962) on the concept of entropy in landscape evolution, the second by R.J. Chorley (1962) on the contributions of systems theory to general geomorphology. Here we have to let apart all what falls under the debate about ‘equilibrium’ (see, e.g., PHILLIPS; RENWICK, 1992; THORN; WELFORD, 1994; BRACKEN; WAINWRIGHT, 2008; PHILLIPS, 2011)32. According to Chorley (1962, p. B2-3), it is the notion of “grade”, taken by Davis from Gilbert, that makes the cycle a not totally closed system. However, « one can see that Davis’s view of landscape development contains certain elements of closed system thinking – including, for example, the idea that uplift provide initially a given amount of potential energy and that, as degradation proceeds, the energy of the system decreases until at the stage of peneplanation, there is a minimum amount of free energy as a result of the levelling down of topographic differences » (CHORLEY, 1962, p. B2). In an earlier publication (GIUSTI, 2012a, p. 61), I criticized the proposition to consider the Davisian cycle as a closed system (and that was a mistake), opposing to Chorley that Schumm and Lichty (1965) took cyclic time33 into account in their multiscale approach of causality factors: “A fluvial system when viewed from this perspective34 is an open system undergoing continued change”. However, a careful re-reading of Chorley’s (1962) paper has shown me that, on the Davisian cycle, the ideas expressed by

32 In my opinion (GIUSTI, 2012b), “graded condition” comes under the theory of the geographical cycle, therefore from an historical and qualitative approach (“time-dependent”, if one accepts the equivalency between “stage” and “time”), while “equilibrium” comes from an ahistorical and quantitative approach (“time- independent”, in a radiometric sense). 33 With Davis, one of the rare mentions of geological time appears in the “Geographical Cycle” (DAVIS, 1899a, in 1909, p. 251): « When it is possible to establish a ratio between geographical and geological units, there will be probably an approach to equality between the duration of an average cycle and that of the Cretaceous or Tertiary times ». At the end of the 19th century, when radioactivity was discovered (1896), the age of the Earth was estimated at only 100 million years: William Thomson, Lord Kelvin, had sharply reproached Darwin for the 300 million years mentioned for the denudation of Weald (HALLAM, 1983, p. 82-109; ORME, 2007). 34 « A landscape that has been tectonically stable for a long time…, […] the long span of cyclic time » (SCHUMM; LICHTY, 1965, p. 113).

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S the author are much more qualified than the simplistic image I had of it then. Actually, we may accept three possible reading levels: the ideal undisturbed cycle is a closed system of interdependent variables (KLEIN, 1960), but if we take into account the “graded condition”, this makes the Davisian cycle a semi-closed system (CHORLEY, 1962), and it could be an open system if one acknowledges the possibility of a “real” cycle incorporating all possible “accidents” (SCHUMM; LICHTY, 1965). Except that, most of the time, Davis has practically often reasoned within the framework of the idealized geographical cycle: this is why a change of paradigm was imperative, either in a qualitative or in a quantitative way. Like the models of Walther Penck and Lester C. King, Davis’s cyclic theory and Klein’s acyclic theory fall 31 into the category of historical models, unlike Hack’s (1960) model which is a “time- independent model” (THORN, 1988). Douglas W. Johnson [1878-1944] edited the “Geographical Essays” (DAVIS, 1909) and also authored two commanding books, the first on the coastal geographic cycle (JOHNSON, 1919), the second about denudation chronology in the Appalachians (JOHNSON, 1931)35. This is why Johnson “held a foremost – almost dictatorial – position in American geomorphology” (CHORLEY, 1965). This strictly obedient Davisian tutored Arthur N. Strahler [1918-2002], whom thesis was defended at Columbia a few months before Johnson’s passing36. After Davisian years, to which the first edition of his textbook on physical geography testifies (STRAHLER, 1951), the reading of Horton (1945) and Mackin (1948) guides Strahler towards quantitative geomorphology (STRAHLER, 1950a; 1950b; 1952a; 1952b). While the premises of plate tectonics occur (GLEN, 1982), which are going to revolutionize the internal geodynamics and the Earth sciences as a whole (HALLAM, 1973; ORESKES, 2003), a no less considerable revolution affects geomorphology and all the external geodynamics. Strahler (1992) himself told the story of this revolution at Columbia. Kennedy37 [1943-2014], who co-authored with Chorley a classic textbook on physical geography (CHORLEY; KENNEDY, 1971), evoked Strahler’s posterity, including Schumm, Melton and Chorley himself (KENNEDY, 2006, fig. 8.2). In the London Basin, a Davisian geomorphology combined with eustatic movements was well established: Davis had stayed in England during the summer of 1894, then taught at Cambridge in 1900 and at Oxford in 1908 (BAULIG, 1950). In 1933, Sidney Wooldridge [1900-1963] invited Henri Baulig to give a series of four lectures on eustatic theory at the Institute of British Geographers38 (BAULIG, 1935). The platforms model of South-East England (WOOLRIDGE; LINTON, 1939) had established the Weald as a typical area of

35 The book received a favorable reception in France, based on a laudatory detailed review (BAULIG, 1932). 36 Strahler’s thesis was defended in 1944, and it concerns the development of the hydrographic network in the Appalachians of Pennsylvania (STRAHLER, 1945). In quite the same area where Davis (1889) had built the foundations the geographical cycle, Johnson had asked Strahler to test hypotheses. In fact, Strahler was quite bored: he considered his effort “largely a waste of time” (STRAHLER, 1992; SCHUMM, 2004, p. 53). 37 M. Church (2014) provided a thought-provoking comment on Barbara Kennedy’s writings: “Read systematically, the work represents a sustained and important critique of the direction taken by mainstream geomorphology since the process‐focused reorientation of the mid‐twentieth century”. 38 Established in 1933, since merged with the Royal Geographical Society (hence the “Transactions of the Institute of British Geographers”).

39 The “Wooldridge and Linton Model” of landscape evolution was dependent on the identification of remnants of three widely developed erosion surfaces: a warped sub-Eocene surface; a high-level unwarped Neogene peneplain and an unwarped Plio-Pleistocene marine platform. It explained both the concordant drainage pattern of the central Weald (through long-term sub-aerial erosion), and the widespread discordant features (as being related to a high-level marine shelf): https://en.wikipedia.org/wiki/Sidney_William_Wooldridge (accessed December 7, 2020). On the evolution of the Weald, see D. K. C. Jones (1999; 2020). About denudation chronology, see Chorley and Haggett (1965), Beckinsale and Chorley (1991), chapters 7, 8 and 9. 40 The British Geomorphological Research Group (BGRG), founded on October 1st, 1960, organized the first international conference on geomorphology (Manchester, 1985), which gave birth to the International Association of Geomorphologists. In 2006, the BGRG changed its name to the British Society for Geomorphology, which has published the journal Earth Surface Processes since 1976, then Earth Surface Processes and Landforms since 1981. 41 H. Baulig (1950) notes that on occasion Davis could even be “agressivement pédagogue”. In Davis’s biography (CHORLEY et al., 1973) one may find words like “propagandist” or expressions such as “the cyclic crusader”. 42 Davis prided himself on being able to imagine many more situations within the geographical cycle than reality can offer: this point was underpinned by both H. Baulig (1950) and R. Chorley (1965). 43 B. Kennedy (2004, p. 402) emphasized that “The two volumes edited by Chorley and Haggett (1965; 1967), derived from the Madingley Hall lectures of 1963 and 1965, were enormously influential”. 44 This is why C. O. Sauer (1925) recalls that a landscape cannot be equated to landforms only, without taking into account the many other attributes, natural and cultural.

Richard Chorley’s Re-Evaluation of Davis (1965) Quote Page To sum up Comment (this paper) Introduction A haze of secondary interpretation producing Mirage effect unreal optical effects The cycle of erosion (COE) concept seems Universal value ‘Cycle of erosion’, not large enough to embrace the whole of 21 ‘Geographical cycle’ geomorphological reality An added distortion results from Davis’ Educational avowedly prime position as a teacher value The stated intention of Davis as conveyed by Explicit his writings formulation The implicit and often unstated assumptions Implicit underlying his work formulation The sometimes-distorted interpretations of Variations Davis’ work stemming from his students The effect of his teaching on succeeding Simplifications generations of geomorphologists The Model The strongest and most compelling features of 22 Also see Chorley (1964) the COE concept is that it presents many of the Theoretical features of a theoretical model dimension (Three properties of this model are): their “A scheme of imagination to be essentially theoretical character, 23 tested” (DAVIS, 1899a, in 1909,

45 See V. Berdoulay (1982, especially p. 579) on the organicist metaphor, and Davis’s anthropomorphism. 46 See Baulig, 1950, p. 19. Davis “built models as he thought the thing should be and thus commanded it to be” (Letter of C. O. SAUER to R. J. CHORLEY, 1961, quoted in CHORLEY et al., 1973, p. 428).

p. 281) […] the inherent need for the discarding or Oriented Over-valuation of cyclic elements ‘pruning’ of much information, selection (that) no part of reality can be uniquely and Non-universality Underestimation of non-cyclic completely built into any one model elements The dogma of progressive, irreversible and sequential change The amount of energy available for the Axiom Hence “Closed System” transformation of landforms is a direct function (CHORLEY, 1962) of relief or of angle of slope 24- Rates of mass transfer by all agencies are 25 greater on steeper slopes than on less steep Corollaries 34 ones Steep slopes are eroded faster than less steep ones, stream velocity is solely dependent on bed slope Rates of change of landforms, as well as their geometrical magnitude, are direct function of local relief Geometry of individual landforms, Rates of Sequential Hence “Youth, Maturity, Old age” their erosional change are both subject to change (DAVIS, 1899a) sequential transformation through time The processes responsible for a given Primacy of Forms of convergence are ignored topographic form and its past history can be 28 landforms deduced from a study of the form itself Geomorphic processes tend often to be viewed Primacy of time Though without any forces, time in an over-simplified manner means nothing (LAPPARENT, 1885) The intellectual setting of the cycle The writings of Herbert Spencer and others “Unilinear Also see Stoddart (1966), Gilson were extending the concept of evolution 29 evolution” (1971), Kennedy (2004), Inkpen and Collier (2007) The idea of organic evolution was one of the “Living Metaphoric, strongly rhetorical most important mainsprings of the cycle of landforms” erosion theory Davis (1885): “a cycle of life” Ibid. Davis (1899a): “The larva, the pupa and the Not in Chorley’s paper, added by us from Davis (1899a, in imago of an insect, or the acorn, the full-grown 1909: 254) oak, and the fallen old trunk” Davis (1922): “a rational, explanatory method ‘Neo-Lamarckian’, not in accord with the evolutionary philosophy of 30 ‘Darwinian’: see Stoddart, (1994), the modern era” Inkpen and Collier (2007). ‘Time’ [...] was viewed not merely as a See Giusti (2006) on Albert de temporal framework within which events occur Lapparent’s geomorphology but a process itself Davis’ synthesis was typical of nineteenth scholarship in general and of geographical scholarship in particular (Ritter) (Davis’ work departed from others in natural To be discuss sciences): in his lack of detailed field observations 31

[...]: his unconcern with details of processes Agreed prompting change (and): in the entirely qualitative nature of his Fully agreed methods “Considering the important question of slope, Verbal logic Bryan (1940), quoted by Chorley he has always substituted words for knowledge, (1965) phrases for critical observation” (The effects of the cyclic approach) was to Idiographic Agreed throw the emphasis upon historical studies of approach special regions The development of the cycle 35 Davis was during the period 1920-34 revising Rejuvenation STRONGLY AGREED (GIUSTI, many of his earlier views 32 2004, 2012b) Ironically, the ‘essential Davis’ are essays prior Going to STRONGLY AGREED (GIUSTI, to 1909 and writings of Douglas Johnson California 2012b) (1919; 1931) Denudation chronology and the cycle Complex and ambiguous (relationship), such 33 Also see Chorley & Haggett, that the two are commonly confused 1965, 148-150 The ‘geographical cycle’ and geography In his last years Davis came to the view that 34 Discussion in Chorley (1965), 35- most of his writings were not strictly 36 geographical in character Table 1 – The elements of a re-evaluation of Davis according to Richard J. Chorley (1965). From left to right: plan of the paper with headings and quotes, page of the quote, summary, commentary.

But the relations between slope and material transfer have proved to be infinitely more complex than the conditions implicitly postulated by Davis, without neglecting the fact that while the changes may be gradual and continuous, they are often neither one nor the other: even disregarding catastrophic events, neither sea level, bioclimatic factors, nor tectonic conditions are stable and immutable. The idea that the processes responsible for a given topography and its past history can be deduced from the landform geometry is only possible provided an excessive simplification, and also to stay eyes wide shut on equifinality (when different processes lead to similar forms). In the geographical cycle theory, even the processes are seen in an overly simplified way (e.g., rainfall): Davis’s master control is time, more than structure and process (DAVIS, 1899a). Davis’s intellectual background is that of a man who built his philosophic and scientific tools according to the ideas circulating in the United States in the second half of the 19th century. The very first and short formulation of the cycle dates from 188447, a note later developed in the paper on the Appalachians of Pennsylvania, then in the geographical cycle paper and repeatedly after (DAVIS, 1885; 1889; 1899a; 1902b; 1905a; 1922). This period is when “the evolutionary theories devised and promoted by paleontologists E.D. Cope and Alpheus Hyatt occupy an important historical position [...], the so-called American school,

47 Geographic classification, illustrated by a study of plains, plateaus and their derivatives (DAVIS, 1885), quoted in Rock floors in arid and in humid climates (DAVIS, 1930, p. 1, note 1).

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S often identified as Neo-Lamarckism” (GOULD, 2002, p. 366)48. As R. Inkpen and P. Collier (2007) pointed out, such eminent figures as Nathaniel S. Shaler [1841-1906], Edward D. Cope [1840-1897] and Alpheus Hyatt [1838-1902] developed “a particularly North American brand of Neo-Lamarckianism… (a) recapitulation theory to understand the evolution of organisms”. Now, just as biologists and zoologists try to describe and classify plants and animals, Davis wanted to establish a principle of classification of landforms which, from a genetic point of view, comes under a neo-Lamarckianism at odds with Darwinian views of change (INKPEN; COLLIER, 2007): Cope’s “phyletic life cycle”, Hyatt’s “old age theory” (GOULD, 2002, p. 369-370). The Geographical Cycle (DAVIS, 1899a) is contemporary with 36 a Hyatt monograph published in 1897, which uses expressions such as “progressive stages of development” or “progressive stages of evolution” (HYATT, 1897, p. 91-92, quoted in GOULD, 2002, p. 370). Hyatt had attended Agassiz’s lectures at Harvard, and from 1886 to 1889 served as an assistant in paleontology at the Cambridge Museum of Comparative Zoology. Professor at Harvard, Shaler49 had been the tutor of Davis, of whom he made his assistant in 1877. All of Davis’s academic career took place at Harvard50, where he was appointed in 1898 Sturgis-Hooper Professor of Geology, a position he held until 1912 (DALY, 1945; BAULIG, 1950). The neo-Lamarckian atmosphere of Boston’s high society, in which Davis spent most of his life before leaving for California, was certainly instrumental in formulating his “orthogenetic” views on a planned systematic development of landforms (INKPEN; COLLIER, 2007). The ideas here analyzed (CHORLEY, 1965) were presented orally during the summer of 1963 at Madingley Hall (the conference center of the University of Cambridge). Although since that date, more than half a century has passed and geomorphology have undergone considerable transformation, Chorley’s proposals remain like many safeguards that no geomorphologist should ignore. Like all great artists, Davis went through creative periods, mainly three: the meteorological and geological writings, the “normal” cycle and its glacial or arid variants, the coral reefs problem and eustatic movements (DALY, 1945; BAULIG, 1950; CHORLEY et al., 1964; 1973; BECKINSALE et al., 1991). The pages relating to the period when Davis devoted himself mainly to meteorology (CHORLEY et al., 1973, p. 145-150) exhibit the deep unity of thought behind the apparent diversity of themes. In an analysis of Ferrel’s51 theory of tornadoes, Davis (1890b) notes that “although led by fact, the theory as a whole is highly deductive or imaginative; but it can fairly be said that the use of the imagination in framing the theory is highly scientific”. An analyst of his Elementary Meteorology (DAVIS, 1894) indicates that Davis’s efforts “were early directed to the explanatory treatment of total phenomena, and toward their rational and systematic

48 About “Alpheus Hyatt: an orthogenetic hard line from the world of mollusks”, see S.J. Gould (2002, p. 365- 383). 49 Shaler’s personality and ideas were evoked in the essay “In a jumbled drawer” (GOULD, 1991, chapter 21). 50 Field-assistant of R. Pumpelly in the North-Eastern Pacific Survey, then appointed (1877) to an assistantship in geology at Harvard, under N.S. Shaler; 1879-1885, instructor of geology; 1885-1890, assistant-professor of physical geography; 1890-1898, professor of physical geography; 1898-1912, Sturgis-Hooper professor of geology, then emeritus (DALY, 1945). 51 William Ferrel [1817-1891] is an American meteorologist who developed a theory of atmospheric circulation at mid-latitudes, whose basic cell is named after him.

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S association, rather than to the instrumental description of items and to the statistical obliteration of non-periodic features” (BRIGHAM, 1909, in CHORLEY et al., 1973, p. 149). The paper on Ferrel’s theory and the textbook of meteorology are placed at the beginning of the “cycle period”, between the paper on the Appalachians of Pennsylvania (DAVIS, 1889) and that on the “development of certain English rivers” (DAVIS, 1895). It is clear that Davis constructs a very different relationship to the physical world from that which characterizes Gilbert’s approach (GIUSTI, 2019). But at a time when so little data were available, can we blame Davis for wanting to follow a path – the creative imagination – other than that of his predecessor, except to behave like a whiggish historian? 37 Concerning geomorphology, several points on which exists a large consensus are the purely qualitative nature of Davis’s methods, his lack of interest in the details of the processes that cause change, and a preference given to historical studies of particular regions. All this can be explained by the foundations of the cyclic theory as it will be examined further. Chorley’s proposition with which I particularly agree is that a correct appreciation of Davis’s system requires consideration of later writings to the Berlin lectures (DAVIS, 1912). During the last period of his long life, and in particular because of his installation in California, Davis revised some of his earlier ideas. It is therefore necessary not to reduce his work to the one and only “geographical cycle” (DAVIS, 1899a), neither to the Geographical Essays (DAVIS, 1909) nor to the books by Johnson (1919; 1931)52. As H. Baulig (1950, p. 23) observed in France (but the following remark undoubtedly has a more general value), “les idées davisiennes, vulgarisées de bonne heure par A. de Lapparent53, ont été acceptées facilement – trop facilement peut-être : on en a retenu quelques principes généraux, des expressions frappantes, des dessins expressifs. Au fond, Davis est chez nous plus célèbre que connu. Et il n’est pas certain qu’on ait tiré de son œuvre toute la substantifique moelle, ni la leçon de méthode qu’elle apportait”. Except, as researchers as diverse as Tricart, Strahler, Birot, Chorley, Stoddart, or Ollier have pointed out, the hypothetico-deductive method and the explanatory description are in fact an essential part of the problem. The point on which it is permissible to depart from Chorley’s analysis is the “lack of detailed field observations” (Tab. 1). David R. Stoddart [1937-2014] had a better view of the subject: when it comes to fieldwork, the problem is less the number of days spent than the way you occupy the study time. Davis “in 1914, travelled extensively in the Pacific, and later in 1923 visited the Lesser Antilles of the Atlantic. Indeed, he travelled too extensively, considering the time at his disposal, and he was not able to stay in one place long enough to work out its entire history” (HOFFMEISTER; LADD, 1935 in STODDART, 1994, p. 31). These journeys to the Lesser Antilles and the Pacific were the subject of extensive cartographic preparation as early as 1913, Davis’s favorite method, as if the role of the terrain

52 H. Baulig (1957, 233) notes about the Geographical Essays of 1909 (the most recent article of which dates from 1906) and the Dover printing of 1954 that “l’ouvrage vient d’être réimprimé tel quel, si bien que l’œuvre de vingt-huit années n’y est pas représentée !”. C. Klein (1997: 126) has extensively cited Rock floors in arid and humid climates, (Davis, 1930, 2), where the cycle is presented as follows: “The groups of forms produced in successive stages of an undisturbed cycle follow in systematic order from the initial stage, when uplift begins, through many sequential stages during uplift and after it ceases, to the long-delayed ultimate stage when erosion is essentially completed”. 53 About French geologist Albert de Lapparent [1839-1908], see Ch. Giusti (2006).

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S was only to allow a choice between different hypotheses developed previously54. This brings us to the very heart of the problem: the “deductive method”, the relationship between theory and facts, the theoretical sketches which end up counting more than field observations, the reasoning to which Davis attributes the rigor of mathematical deductions and in which he locks himself up. On the contrary, in his analysis of The Coral Reef Problem (DAVIS, 1928), de Martonne (1929), underlined that “c’est du rapprochement de l’idée et du fait que jaillit la lumière”, and not from the strict separation of facts and theory, praising Davis himself for not sticking to his rule. Then de Martonne (ibid.) adds: “Le plus souvent, c’est l’observation d’un fait inexplicable par une théorie qui oblige à l’abandonner et met sur la voie d’une nouvelle 38 explication”55. This is why Davis’s successors have insisted on facts left in the shade and on situations too quickly dismissed: “Since his deductions, expressed in sequential block diagrams, were based on his incorrect belief that elevated reefs eroded rapidly, Davis was compelled to reject paleontological evidence that many elevated reefs are old. Thus, to support his theoretical position he systematically misrepresented the geomorphic history of, for example the Lau Islands, Eua, the Loyalty Islands, Jaluit Atoll and Mangaia” (STODDART, 1994). If there is a misconception not to be made, it is to see Davis as a Darwinian, as his advocacy for Darwin’s conceptions of coral reefs might suggest (KENNEDY, 2004). R. Inkpen and P. Collier (2007) have shown that for Davis, the word “evolution” is basically just a broad inclusive metaphor, under the umbrella of which he places both the living and the inorganic. Thus, the abiotic reign has its “living things”, like the geographic region and the river, which follow linearly their cycle of life, in predictable and differentiated stages. This is why Davis ascribes particular importance to certain regions and certain attributes (the Appalachians, their rivers, the associated valleys), and why he does not care about accidents that could interrupt the course of the cycle: movements of the soil, climate change, volcanic eruption. In such a case, “The previous cycle is thus cut short and a new cycle is entered upon” (DAVIS, 1905a in 1909, p. 285)56. The “normal” course of the cycle refers less to humid temperate climatic conditions than to the absence of any disturbance of the ideal cycle (and of course, the abnormality57 being the glacial climate and the arid climate). Rivers (ice, wind) and regions are geographic beings, landscapes are families of geographic landforms linked to the advancement of the “normal” (glacial, arid) cycle and time is not a measurable quantity (quantitative time) but successive stages of development (qualitative time). But there is nothing in common between the development of landforms and the life of organic beings, because a group of landforms is not a biological population. The “organicist metaphor”

54 This preparatory work is the subject of a three-part paper: The home study of coral reefs (DAVIS, 1914). 55 This is expressed in a slightly different way by S.J. Gould (2000, p. 104-105) who, with regard to the principle of objectivity, returns to the articulation of facts and theory: “A major, and harmful, myth of science — engendered by a false interpretation of the eminently worthy principle of objectivity — holds that a researcher should just gather facts in the first phase of study, and rigorously decline to speculate or theorize (…). Objectivity cannot be equated with mental blankness; rather, objectivity resides in recognizing your preferences and then subjecting them to especially harsh scrutiny — and also in a willingness to revise or abandon your theories when the tests fail (as they usually do)”. 56 About the « Interruptions of the Ideal Cycle », see Davis (1909, p. 272-276 and 285-292). 57 Davis (1909, p. 288) writes “special agencies, namely ice and wind”.

(BERDOULAY, 1982) used by Davis is therefore not just a simple figure of speech (GIUSTI, 2004), but the expression of a deep conviction: that the theory of the geographical cycle was the key to access the laws of all morphogenesis, from the development of individuals (river, slope, valley) to the various families (normal, glacial, aeolian) of landforms in their full spatial extent. There is nothing more different than the random and contingent Darwinian development of living things than the orderly and systematic Davisian development of stages.

3. CODA

These two reassessments continued to live in parallel, remaining independent and 39 isolated due to the barrier of language. The year 1973 was marked by the publication of the monumental biography of Davis (CHORLEY; BECKINSALE; DUNN, 1973) and by the defence of an impressive thesis58 published shortly after (KLEIN, 1975). However, extensive surfaces of planation exist, and they remain a major issue: it is more difficult to explain the origin and the persistence in the landscape of the surfacic forms of great extent such as the large continental plains of erosion (e.g., SUMMERFIELD, 1991; WIDDOWSON, 1997; BURKE; GUNNELL, 2008), than the location of large volumic mountain chains linked to the combined effects of the global tectonics and the climatic forcings (e.g., MOLNAR; ENGLAND, 1990 ; SUMMERFIELD, 2000), active mountain chains some of which bearing neatly characterized flat elements (CALVET; GUNNELL; FARINES, 2015). Not suspect of complacency about Davisian geomorphology, C. Ollier recalled it with a touch of irony: “Most people who are not blind or stupid can tell when they are in an area of relatively flat country: they can recognize a plain when they see one. For some reason, erosion surfaces have come to be regarded as either mythical or old-fashioned concepts, especially by English geomorphologists, and even their existence is denied” (OLLIER, 1991, p. 76). As Chorley has pointed out (Tab. 1), the geographical cycle and the denudation chronology are so interweaving (CHORLEY, 1965) that the abandonment of the first has mechanically resulted in the rejection of the other: “Davis’s theoretical techniques involved the embracing of an initial conclusion, largely from studies of maps, and then in justifying this conclusion by argument and a minimum of carefully selected field observations” (CHORLEY, 1978, p. 5. Also see STODDART, 1994). On the other hand, with regard to the action of rivers, this key element of the cyclic theory, Chorley (2000) insists on the fact that a river is “a multivariate, nonlinear, process-response system”, and that this also applies to all the interfluves: “The cycle of erosion implied linear change in a repeatable context but, as Gilbert and others recognized, denudation is a nonlinear process subject to accelerations, decelerations, and thresholds”. It was therefore preferable to rebuild on different bases and with new tools. The “Mid-century revolution in fluvial geomorphology” (CHORLEY, 2008) is a total paradigm shift: “So long as the tools a paradigm supplies continue to prove capable of solving the problems it defines, science moves fastest and penetrates most deeply through confident of

58 Klein's thesis was defended at the Université de Bretagne Occidentale (UBO) in Brest on April 5th, 1973, before a jury including geologists Louis Chauris and Louis Dangeard, and geographers Pierre Birot, Jean Dresch and André Guilcher. In spite of twenty years of shared enthusiasm and mutual collaborative work (1977-1997), I failed to convince my tutor of publishing at least one review paper in English on the acyclic theory.

Year Quantitative Qualitative Title approach approach 1945 HORTON Erosional development of streams and their drainage basins: hydrophysical approach to quantitative morphology 1948 MACKIN Concept of the graded river 40 1950a BAULIG Essais de géomorphologie 1950b BAULIG William Morris Davis, master of method 1950a STRAHLER Davis’ concept of slope development viewed in the light of recent quantitative investigations 1950b STRAHLER Equilibrium theory of erosional slopes approached by frequency distribution analysis 1951 KING South African Scenery 1952 BAULIG Surfaces d’aplanissement 1952a STRAHLER Dynamic basis of geomorphology 1952b STRAHLER Hypsometric (area-altitude) analysis of erosional topography 1953 PENCK Morphological analysis of landforms 1953 KING Canons of landscape evolution 1955 BIROT Les méthodes de la morphologie 1956 BAULIG Pénéplaines et pédiplaines 1956a SCHUMM Evolution of drainage systems in badlands at Perth Amboy, New Jersey 1956b SCHUMM The role of creep and rainwash on the retreat of badland slopes 1957 MELTON An analysis of the relations among elements of climate, surface properties, and geomorphology 1957 BAULIG Les méthodes de la morphologie d’après M. Pierre Birot 1958 BAULIG La leçon de Grove Karl Gilbert 1958a MELTON Geometric properties of mature drainage systems and their representation in an E4 phase space 1958b MELTON Correlation structure of morphometric properties of drainage systems and their controlling agents 1959 BAULIG Morphométrie 1959a KLEIN Surfaces polygéniques et surfaces polycycliques 1959b KLEIN Surfaces de regradation et surfaces d’aggradation 1960 KLEIN La notion de rythme en morphologie 1960 HACK Interpretation of erosional topography in humid temperate regions 1960 BIROT Le cycle d’érosion sous différents climats 1962 BRETZ Dynamic equilibrium and the Ozark land forms 1962 LEOPOLD & LANGBEIN The concept of entropy in landscape evolution 1962 CHORLEY Geomorphology and general systems theory 1964 LEOPOLD, Fluvial processes in geomorphology GORDON WOLMAN, MILLER 1965 CHORLEY A re-evaluation of the geomorphic system of W.M. Davis 1965 SCHUMM & LICHTY Time, space, and causality in geomorphology Table 2 - The re-evaluations of the Davisian system: scientific context (1945-1965)

Robert Elmer HORTON (1875-1945); Henri BAULIG (1877-1962); J Harlen BRETZ (1882-1981); Walther PENCK (1888-1923); Joseph Hoover MACKIN (1905-1968); Walter Basil LANGBEIN (1907-1982); Lester Charles KING (1907-1989); Pierre BIROT (1909-1984); John Tilton HACK (1913-1991); Luna Bergere LEOPOLD (1915-2006); Arthur Newell STRAHLER (1918-2002); John Preston MILLER (1923-1961); Claude KLEIN (1924-2005); Markley GORDON WOLMAN (1924-2010); Richard John CHORLEY (1927-2002); Stanley Alfred SCHUMM (1927-2011); Mark Aldridge MELTON (1930-2019).

As a jury of Jean-Claude Flageollet59 [1931-2014] and because of close friendship with René Lacotte [1924-2002], Klein had to take up the detailed study of the Limousin soon proposed as a “géomorphotype” (KLEIN, 1978; DÉSIRÉ-MARCHAND; KLEIN, 1986). As Klein points out in the conclusion of his 1986 paper, “l’étude des bordures occidentales du 41 Bassin de Paris et des parties adjacentes du Massif armoricain nous avait mis en présence d’un exemple remarquablement démonstratif de substitution dans le temps du mode cyclique au mode acyclique [...]”; in conjunction with the Brenne and its inherited forms of aggradation, “le Limousin nous permet aujourd’hui d’analyser un exemple non moins parfaitement caractérisé de substitution dans l’espace d’un mode à l’autre” (DÉSIRÉ- MARCHAND; KLEIN, 1986, p. 45)60. It is quite easy to understand that the acyclic mode of evolution thus conceived offers a solution to the enigmatic origin of extensive palaeosurfaces, a proposal that should have been widely discussed. If some of Klein’s French colleagues preferred to follow the climatic school (Tricart), the littoral school (Guilcher), the karst school (Nicod), the tropical school (Demangeot), the Mediterranean school (Birot), the basement school (Godard), Klein remained himself faithful to Davis (the cycle), Baulig (the eustatic rhythms) and Penck (the tectonic rhythms). In his latest works, Klein (1993; 1997; 1999) attempted to modulate both in space and time the respective share of the cyclic (Davis), polycyclic (Baulig), and acyclic (Penck) modes of evolution. The Brenne and the Monts d’Ambazac are the morphological units through which the formations and the problems studied by Klein (1975) in his thesis connected to the various regions of the Central Plateau (KLEIN, 1990). There, the succession of the cyclic mode to the acyclic mode of evolution occurred either locally in the areas affected by the Eocene updoming, or at large during the Miocene, Pliocene and Pleistocene waves of successive erosion. At this point in the paper, it would be easy to see in Claude Klein just a system maker, an isolated Davisian monadnock, surrounded by the high tide of the new geomorphology in the second half of the 20th century. Klein (1999) explained how Baulig was stuck in the trap of an antagonistic double fidelity to Suess (diastrophic eustatism) and Davis (oceanic fixity and “rapid-uplift/prolonged-stillstand” model). However, it seems that Klein placed himself in a situation of comparable discomfort, due to his dual loyalty to Davis and Penck: as his thesis supervisor noted, Klein “ne suit ni Davis ni Walther Penck, mais son acyclisme se défend de l’un comme de l’autre, encore que le second l’ait assez fortement influencé” (GUILCHER, 1974). In Klein’s opinion, “Penck a choisi de fonder ses propres analyses sur des situations de déséquilibre entretenu, en conférant à la composante endogène de la morphogenèse une prééminence telle que la marche de l’érosion elle-même se trouve être en permanence

59 J.-C. Flageollet (1977; 1979). C. Klein (1978). J. Désiré-Marchand and C. Klein (1986). 60 In the Southern Massif Central (GIUSTI, 2002), while polycyclic evolution appears relatively early on the Mediterranean slope, acyclic evolution continues relatively late on the Atlantic slope.

William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020 GIUSTI, C. TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S contrôlée par elle. Au système clos de variables interdépendantes proposé par Davis, Penck a substitué un système ouvert dans lequel l’une des variables, la tectonique, voit son efficacité croître ou décroître graduellement, en toute indépendance, en imposant sa loi à tous les autres facteurs de la morphogenèse sans dépendre aucunement d’eux” (KLEIN, 1984, p. 76). This long but essential quote, in particular the adverb “graduellement61” (and also one of the illustrations, taken directly from Davis), shows that Klein reads Walther Penck through Davis (1932) and Baulig (1939): the truth is Penck wrote “constantly accelerated” (GIUSTI, 2012b). Having said that, even if Klein has not read Tuan (1958), Hack (1960) or Simons (1962), he has perfectly learned the Penckian lesson of Pierre Birot, and Klein’s acyclic theory is rather 42 “Darwinian” when Davis’s cyclic theory is clearly “Neo-Lamarckian”. It is simply regrettable that Klein (1990; 1997) has too easily come to terms with his model of Eocene updoming62, because even by sticking to only French-language writings, it would have been possible for him to take more account of contributions from the “basement school” (GODARD et al., 2001), geophysics data (BATTIAU-QUENEY, 1984; 1988; 1989)63, or new dating techniques (GUNNELL, 1996; 1997). To sum up, Klein’s acyclism less belongs to Davis and Baulig than to Penck and Birot: on the one hand, the acyclic mode of evolution is an open system in which events are contingent, the scenario unique and unpredictable; on the other hand, Klein’s “équilibres mobiles” are characteristic of a “déséquilibre entretenu” (maintained disequilibrium) and, therefore, they are in relation not with the “graded condition” of the old Davisian framework but with the “dynamic equilibrium” of the new Hackian framework reviving the Gilbertian legacy (Tab. 2). And so, acyclism remains a valid concept that could help to understand the permanency of large paleoplains out in the landscape (GIUSTI, 2012b). After Penck’s English translation (1953), numerous writings on Davis appeared (JUDSON, 1960; CHORLEY, 1965; FLEMAL, 1971; CHORLEY; BECKINSALE; DUNN, 1973; BIROT, 1974; DAVIES, 1975), followed by book chapters on the history of geomorphology (e.g., MELHORN; FLEMAL, 1975; TINKLER, 1985; THORN, 1988; BECKINSALE; CHORLEY, 1991; SUMMERFIELD, 1991; OLLIER, 1991; RHOADS; THORN, 1998; KLEIN, 1997; KENNEDY, 2006; GOUDIE, 2011), or by specialized papers (e.g., SEVON, 1983; KLEIN, 1985; MORISAWA, 1989; STODDART, 1994; PHILLIPS, 2002; OHMORI, 2003; PEULVAST; CLAUDINO-SALES, 2005; INKPEN; COLLIER, 2007; ORME, 2007; EBERT, 2009; GREEN et al., 2013; PHILLIPS, 2015; GUNNELL, 2020).

61 The adverb “gradually” is quite often the sign of an unconscious form of uniformitarianism, an implicit acceptance of the non-actualist principle of “uniformity of rhythm”: (GOULD, 1965; 1987, p. 118-126 and 174- 178; GIUSTI, 2012b, box 3, p. 29-32). 62 See C. Giusti (2002, p. 441-461). 63 In his latest writings, C. Klein often refers to the large synthesis of his colleagues at the Sorbonne on geodynamics and structural geomorphology, J.-P. Peulvast and J.-R. Vanney (2001-2002).

Despite this large number of works, I doubt Davis’s thought to be really better known. First obscured by celebrity, Davis’s geomorphology is today’s veiled by simplistic and reductive clichés, so that two key concepts need to be commented on as a conclusion.

 “Geographical cycle”. – Just as Darwin never used the word “evolution”, Davis never used the expression “cycle of erosion”. Davis’s (1899a) choice of “geographical cycle” is explained by the fact that he was not concerned with measuring the thickness of the regolith along the slopes or the load of the rivers (although rivers were the engine of the stages succession). Davis’s purpose was to follow the development of an 43 ordered succession of landscapes (in “normal”, glacial, or arid conditions), with landforms corresponding to the programmed stages of the degradation of an initial relief within the semi-closed system of an undisturbed cycle. And all that deals with geography as a spatial science, hence the “geographical” cycle. And one of the major problems of current geomorphology is a tendency to cut off from landforms in the field by using only numerical techniques and minoring the landscape component64 to the sole benefice of the tectonic and climatic-laden forcing. The geologists who decided long ago to substitute “erosion cycle” for “geographical cycle” inaugurated a long tradition which has continued despite Davis and reinforced since the quantitative turn of the 1950s.  “Peneplain”. – Most geologists and geomorphologists who use this concept today do so without imagining exactly what it means, namely a series of “gently rolling swells alternating with shallow valleys” (DAVIS, 1899b), not a plane but a corrugated topography. Too often, “peneplain” is assimilated to a plane, a geometric line, a “surface of erosion”, an expression which means so many things that it complicates the problem instead of helping to solve it (unless you be one of the people hiding the problem under the rug). It was Johnson who in 1916 proposed to replace “peneplain” by “peneplane”, to which Davis replied in 1922 that a “surface of ultimate degradation” would not be “a plane” but “a plain” (BAULIG, 1956b, § 160). Johnson’s fault with which to blame is to apply “peneplane” to any planation surface regardless of its origin. And the same error is made by those who apply “peneplain” to all forms of planation: the ones which have become flat by reduction of an initial volume of relief, or the ones which are plane from birth and succeed in remaining so during a long period of time. However, a “lowland”, an “almost plain”, a “peneplain” (Davis), a “peneplane” (Johnson), a “Primärrumpf” or an “Endrumpf” (Penck), a “panplain” (Crickmay), an “etchplain” (Wayland), a “pediplain” (King), a “plaine d’érosion” (Baulig), a “doppelte Einebnungsfläche” (Büdel), an “acyclic surface” (Klein), a “stripped etch surface” (Thomas), are specific landforms, whether functional or inherited from the past. These surfacic landforms exhibit in some cases a noticeable flatness, and sometimes the physical appearance of a hilly landscape. And of course, all these topographies have a different origin. Therefore, rather than continuing to use “peneplain” which, even as a descriptive term, creates a lot of confusion, it would be far better to use neutral, non-genetic terms such as “paleoplain” (OLLIER, 1991) or “palaeosurface” (WIDDOWSON, 1997).

64 The landscape dimension is at the center of the superb book by P. Migoń (2010), Geomorphological Landscapes of the World, and of the series he heads at Springer: World Geomorphological Landscapes.

All the elements are available which make it possible to understand the Davisian system for what it is: a qualitative, historical and theoretical model, elaborated by a brilliant teacher. Many authors have praised the limpid prose and luminous drawings of Davis65, who impeccably mastered the art of teaching and discussion, that “research by debate” (DAVIES, 1975) in which Baulig also excelled. Davis’s meteorological writings and his travels around the world (CHORLEY; BECKINSALE; DUNN, 1973) leave me doubtful when faced with the reproach of a mind that has been closed to numbers or realities on the field. After having read some of Davis’s texts for forty years or so, and thanks to the authoritative works published on them (books, papers), my own feeling is that the father of the “geographical 44 cycle” was convinced he had found both a method and a principle – the “explanatory description” and the “stage” – explaining the development of landforms in space and over time. That his educational gifts have carried Davis towards ever greater idealization is also a reality that everyone should be aware of when using any of the concepts of the rich Davisian system. Davis multiplied the scenarios and really used the multiple hypothesis method, alas ever and ever within the constrained framework of the ideal cycle. Geomorphology scientists who wish to venture into the heart of the Davisian supercontinent are sure to find as many wonders there as in the glittering caves of Aglarond. But they will have to come out quick and adopt a critical distance from the strange jewels of their treasure hunt. The spatial dimension of the geographical cycle explains why many authors today turn to the dated and somewhat overused concept of peneplain, for geomorphology cannot be limited to a system of equations or to a series of functions. It would be futile to fight a theory such as the Davisian system: it is better to get to know it and take it for what it is, an endless metaphor, a way to approach qualitatively difficult problems, then to move on the quantitative ground with the dating of forms, deposits, concretions, the quantification of processes, forces, transfers of mass and energy. The problem is not the adoption or rejection of the Davisian system, but its relevant use. Just as Euclidean geometry is a possible introduction to all other geometries, Davisian geomorphology is a possible introduction to all other approaches in geomorphology, and to the study of landforms in their geographic dimension.

REFERENCES

BATTIAU-QUENEY, Y. “Constraints from deep crustal structure on long-term landform development of the British Isles and Eastern United States”. Geomorphology, 2, 1989, p. 53- 70. https://doi.org/10.1016/0169-555X(89)90006-8.

BATTIAU-QUENEY, Y. “L’évolution géomorphologique du Piedmont appalachien et de la Plaine côtière, du New Jersey à la Géorgie”. Cahiers de géographie physique, N°6. Travaux du Laboratoire de géomorphologie et d’étude du Quaternaire. Lille, USTELA, 1988.

65 The educational value of Davis's drawings is such that a selection of his most demonstrative sketches has been published by P.B. King and S.A. Schumm (1980), along with explanatory and analytical comments.

BATTIAU-QUENEY, Y. “Structure profonde, tectonique des plaques et grands ensembles géomorphologiques : l’exemple des marges appalachienne et britannique de l’Atlantique nord”. Hommes et Terres du Nord, 3, 1984, p. 139-148. https://www.persee.fr/doc/htn_0018-439x_1984_num_3_1_1942.

BAULIG, H. “Morphométrie”. Annales de Géographie, 68, 369, 1959, p. 385-408. https://www.persee.fr/doc/geo_0003-4010_1959_num_68_369_15984.

BAULIG, H. “La leçon de Grove Karl Gilbert”. Annales de Géographie, 67, 362, 1958, p. 289-307. https://www.persee.fr/doc/geo_0003-4010_1958_num_67_362_16949. 45 BAULIG, H. “Les méthodes de la géomorphologie d’après M. Pierre Birot”. Annales de Géographie, 66, 354, 97-124 et 355, 1957, p. 221-236. https://www.persee.fr/doc/geo_0003- 4010_1957_num_66_354_18261 and https://www.persee.fr/doc/geo_0003- 4010_1957_num_66_355_18274.

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BAULIG, H. “Vocabulaire de la géomorphologie”. L’Information Géographique, 19/2, 1955, p. 72-80. https://www.persee.fr/doc/ingeo_0020-0093_1955_num_19_2_1477.

BAULIG, H. “Cycle et climat en géomorphologie”. Rennes, 50e anniversaire Laboratoire de Géographie, Volume jubilaire (1902-1952), 1952a, p. 215-239.

BAULIG, H. “Surfaces d’aplanissement”. Annales de Géographie, 61, 325, 161-183 et 326, 1952b, p. 245-262. https://www.persee.fr/doc/geo_0003-4010_1952_num_61_325_13392 and https://www.persee.fr/doc/geo_0003-4010_1952_num_61_326_13421.

BAULIG, H. “Géomorphologie davisienne”. L’Information Géographique, 15, 1951, p. 93- 100. https://www.persee.fr/doc/ingeo_0020-0093_1951_num_15_3_1070.

BAULIG, H. Essais de géomorphologie. Paris, Les Belles Lettres (voir aussi William Morris Davis: Master of Method, Annals of the Association of American Geographers, 40, 3, 1950, p. 188-195). https://www.tandfonline.com/doi/abs/10.1080/00045605009352067.

BAULIG, H. “Sur les gradins de piedmont”, Journal of Geomorphology, 2, 1939, p. 281- 304.

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William Morris Davis - Revista de Geomorfologia, v. 1, n. 2, 30 de dezembro de 2020, p. 21-59. DOI: https://doi.org/10.48025/ISSN2675-6900.v1n2.p/21-59.2020