FORM, PROCESS AND MATER|ALS Approaches to a central concept of íorřr], process and materials have focused on processes, landform evolution, and climatic geomorphology. Although these developed separately until the late 20th century a more holistic approach has recently brought them toqether, especíally fosteíed by multidisciplinary research. lt is now appreciated that advances in mac roscale geomorphology have enabled lar*e scale landform developments to complement sma/lsca/e process research. UsínÉcoverin€ law models of explanation, it ls possibie to recognize geoÉraphical, geophysical macro Eeomorpholo€jy, and historical approaches Landform is the subject matter for geornorphology as the landform science, so that it follows that a central concept is the relationship of landform, process and materials. Although manifested in various ways over the last one hundred and fifty years years it has not frequently been stated explicitly. However, it has been presumed, although some have recognized a growing emphasis on the 'mutual interaction between form and process in the understanding of geomorphological systems' (Roy and Lane, 2003 ). This chapter provides a summary of interrelationships (5.1); indicates how distit-tct concepts emelged during the progressive development of geomorphology (5.2); and surveys the present position (5.3). 5.1 Relating form, process and materials The relationship between these three characteristics of the Earth's surface can be summarized by a simple geomorphological equation, adapted from a physical geography equation (Gregory, 1978a) subsequently accepted by a number oí writers including Yatsu (1992) and Richards and Clifford (2011). The equation was devised to indicate the way in which processes (P) operating on materials (M) over time t produce results expressed as landforms (F).In equation form it can be expressed as: F=f(P,M) dt 46 sY§íEM c{)|tTExTs Geomorphological investigations can be visualized as concerned with five levels of enquiry as summarized in Box 5.1. A way of summarizing geomorphology (see Gregory 1985; 2000; 2009) A geomorphological equation, ]ndicating hoW processes operating on materials over lime 1 produCeS resrlis expressed as a landform, can be expressed aS: F=f(qN/) dt lnvestigations can be made at five levels| Level 1: study of the elements or com ponents of the equatíon , study of the components in their own right. Some studies can be foCUSed on the descr ption, Which nray be quantitat]Ve, of landforms, oí Soil or rock characte1 or of plant commUnities, Level 2: balancing the equation study oíthe Way in Which the eqUat]on is balanced at different scales, At the continental level may inVolve the energy balance relating aVailable energy for enVironmental processes to radiation, and n,]oisture received in relation to |ocally avai|able materialS. StUdies of thiS kind focus upon Contemporary environments and Upon interaction between processes, materials and the resulting landforms or environmental conditions, Level 3: dífferentiating the equation - inCludes stUd]es analysing how relationships change over time. This reqUires reconciliation of data obtained from d]fferent iime Sca|es together With a conceptual approach, lncludes impact oíclimate change and hUman activity Which may be ihe regu|ator that has creaied a Contro] system. Level 4: applying the equation When research results are applied to problems, Very often extrapolating past trends, encountering the ditficUlty of extrapolating from paňicUIar spatiaI or temporaJ scales to other scales for Which iníormation is reqUired to address management problems. Level 5: apprecíating the equatíon - invo|Ves acknowledging that hUman reaction to physical environment and physical landscape can Vary between cultures, alfecting how the earth'S sUrface is managed and designed Fo 5.2 A theme p]evaili geomoíphology and During the course of the d an alternation of catastro1 on landform relationships a sequence of geomorphol inevitable that such appro: as erosion, landscape chan; as a geomorphological 'bal sequence of paradigm shitrs on form, process and materi Clifford, 2011), but unders to appreciate how the,v ea, phology. Whereas we are nc tion in geomorpholog1, {e.g originated when it took mu ent languages, there u,ere c scientific meetings, fe§, scie and dissemination of idea: scholars concerned with inr It is not easy for a smc multifarious strands that h: that we require a convenie of the major founding der, of developments in other time, permeating geomorP the main strands of thinki materials and underpinnin1 more difficult is divining thr strands, and ascertaining t independently in different this kind is needed to ensrl communication is not obl re-invent the wheel! There development of geomorph< The inclusions in Table mented and extended. The climatic variety - are integl tems, developments in oth ocean cores stimulatin8 r§ and the availability of oth, dating. Each of the maic F(]FM. PHOcEss AND MATtRIALs 5,2 A theme prevailing in the development of geomorphology and landform science Durilrg the course of the developnent of urriformitarianisn there wirs an alternation of catastrophisn and gradualism, but once the focus on landforrr. relationsl-rips with processes and materials was embraced a sequence of geomorphoJogical approaches evolved. It was perhaps inevitable that such approacl-res would each have a major driver, such as erosiot-t, landscape change or climatc. Pcrrtrayed by Jennings (1973) as a p;eomorplrological 'bandwagon parade', this can be thougl-rt of as a sequence of paradign shiťts (Gregor,v, 2010: 3.5, Table 2..5). The emphases on form, process and materiaIs have changecl over the ycars (Richards and Cliíford, 201 1), but understanding the developing sequence is ncccssary to appleciate bow tlrey each affect contempofary thinking in gcourtlrphology. \X/hereas wc are norv familiar with extremely rapid comnlunication in geomorphology (e.g., Gregory et al., 2013) diífcrent approaches oriE;inated when it took much longer to surmount the obstacles of different lrrnguagcs, thcre were compalatively few national and intcr:national scicrrtific meetings, few scientific journals íor the publication of research arrd dissemination of ideas, and few researchers in the connrunity of scholars concerned with investigations of the surface of the Earth. It is not eas1, for a student in the 21st centuíy to conprehend tl-re multifariorrs strands that have produced the geomorphology of today, so that we require a convenierrt way to encapsulatc thc inter-relationship of the major founding devclopncnts, and to set tl-rem into the context of developnlcnts in other discipliries r,vhich were so iníluential at the time, permeatir-rg geornorphology and othcr sciences. Table 5.1 shows the main strands oí thinking identified to focus on fornr, process and materials and underpir-rning thinkirrg in geornorpholog,v. '§řhat is much n-rore difficult is divining thc Iinks that have occurred between the seyera1 srrands, and ascertaining the extent to rvhich similar ideas developed independently in djfferent places. However, a map of past activity of this kind is needed to ensurc that the modern outburst of literature and communication is not oblivious oípast contlibutions - we must llot re-inyent the wheel! There is practical value in knowing the historical development o{ geonorphology (Sack, 2002). The inclusions in Table 5.1 provide a framework that can be augnented and extended. Thc threc major themes - process! evolrrtion and climatic variety, are integrated with external trends which include systems, developments in other disciplines such as hydrology, analysis of ocean cores stimulating research in Quaternary science, renlote sensing and the availability of other teclrniques including GIS and cosmogenic dating. Each of the major themcs is explained in detarl elsewhere 47 48 SYSTEM CONTE)(TS (e.g,, Summerfield, 1991; Gregory, 2000, 2010) and expanded in later chapters (11, 15), so that a brief outline is provided here. The process theme dates from when there was a debate about how the Eartht suríace was fashioned, and when actualism and gradualism succeeded catastrophism (see Chapter 3). However the main strand derived from the work of G.K. Gilbert (1843-1918), one of the explorers of the American '§íest, who from the ].880s were demonstrating the power of subaerial erosion in producing landforms. In his later work Gilbert used analogy with physical mechanics and studied landforms as manifestations of geomorphic processes acting on Earth materials (Sack, 1991:30), with the result that he is now acknowledged to be a brilliant geomorphologist who published a remarkable investigation on the Transportation of debris by running uater ín 1,914, anticipáting many developments that did not occur until nearly fifty years later. Although there were some subsequent fluvial contributions it was not until 1964 with the publication oí Fluuial Ptocesses in Geomorphology (Leopold et a|., 1,964) that a new era of process investigation became widespread, emphasizing physical principles, dealing 'primarily with landform development under processes associated with runnin8 water . . . better future understanding of the relation oíprocess and form will , . . contribute to, not detract írom, historical geomorphology'. Parallel with the interest in fluvial processes wefe other strands: coastal, glacial, and aeolian, the latter stimulated by a book on Púysics of Blotun Sand and Desert Dunes (Bagnold, 1941). The second theme, labelled evolution, and possibly influenced by Darwinian evolution (1859), was intfoduced in 1895 by'§í.M. Davis (1850-1934). §7ith the benefit of hindsight we now realize that his approach gave insufficient attention to the formative processes operating, was essentially qualitative in approach, focused on parts of the land surface and ignored others, and did not have a sound scientific foundation (see Chapter 11, Box 11.1, Table 11.1); however, his work was very intelligible and persuasively presented. The essence of his approach, which appealed to persons with little training in basic physical sciences, was that landforms are a Íunction of structure, process and time, and evolve through stáges of youth, maturity and old age. This conceptual model was devised for a'normai'cycle of erosion applied to temperate landscapes, but alternatives of arid and marine cycles were also proposed, and in the course of landscape evolution there could be accidents, either glacial or volcanic. Land surface was interpreted in terms of the stage reached in the cycle of erosion and came to be dominated by a historical interpfetation concentrating upon the way in which landscapes had been shaped during progression through stages in a particular cycle, towards peneplanation. Followers of this approach therefore attempted to identify the stages of long-term evolution of landscapes - an approach later f0 termed denudation chrono of Davis's influential essal,s cational essays and 14 ph_v: Davis had in geographical existed at the time, and the 12 reasons (Higgins, 1975l followed by others (see Cl ized as 50 canons of lands approaches to landscape er which landscape had been i (see Chapter 13), the Caint and the Quateínary. Althou was being investigated duril glacial and later in periglaci in dating that Quaternan ! as a separate field. A climatic focus probab tists such as Dokuchaer | 1 fied broad zonal patterns c surface of the Earth into r different landforms occur ogy found favour in Europ way thát Soil and vegetador reflecting also the morphoc 1,9 57). In qualitative term if they were associated tl nal belts, whereas azonal 1 resulting from endogenetic occurring beyond their nol coasts rather than desens: can operate in all areas oí physical laws. Such zonalin zones (Tricart and Cailleu: tion was used to provide a zonality. Subsequently, thíl were recognized (Bůdel, ll duced in Germany which h Holzner and §7eaver (1965 nate in eight climato-morpl genetic systems was introdr distinguished by a characte stimulating interest in perig It might appear that matt cess and form, although an t Ft)H[|, PH()cEss AN0 i,lÁTEBlÁ ts termed denudatiorr chronology (see Gregory,2000: .]8-42). A collection of Davis's influential essavs arrd papers (Johnson, 1953 ) included 12 educational essays and 14 physiographic essays. This shows the intercst that Davis lrad in geographical teaching, fulfilling the substarrtial need that existed at the time, and the popularity of his approach was attributed to 12 reasons (Higgins, 197_5) lvith simplicity the first! This approaclr rvas followed by othcrs (see Chapter ] 1), with that of Lester King íornal ized as -50 canons of landscape evolution (King, 1953: 747-5()). Thesc apploaches to landscape evolutiot-t largely concentrated on the ways in which landscape had been fashiolred in thc later stages of geological tirr-re (see Chapter 13), tlre Cainozoic, including the Palaeogene, the Ncogene and tl]e Quaternary. Although the analysiS of Quaterllary glacial irnplcts was being investigated during the 20th centur1,, generating rcsearchers in glr,rcial and later ir-r pcriglacial geon.orphology, it was lvith inlprovenents in dating that Quaternary Science really flourished and began to evolve as a separate field. A climatic focus probably had its origins in Rrrssia lvhele soil scierrtists such as Dokuchaev (1846-1903) and his student Sibirtsev identified broad zonal patterns of soils related to climate. Dividing the land surface of the Earth into major zones as a basis íor considcring l-row diíferent landforms occur in lvorld landscapes, climatic geomorphology found íavour in Europe and Russia because it could en-rbrace the Way that soil and vegetation types are associated r.vitlr particular zclnes, reflecting also the rnorphoclimatic zones recognized in France (Tricart, 7957). In qr"ralitative terms, phenomena could be regarded as zonal if they were associated with the climatic characteristics oí latitudinal belts, whereas azonal phenonena are non-climatic such as those resultir-rg írom endogenetic processes; extrazonal phenomena are those occurring beyond their nornral climatic limits sr-rcl-r as sand dunes on coásts rather than deserts; and polyzonal phenomena are those u,hich call opeíate in all areas oí thc Earth's suríacc according to tbe slrme physical laws. Such zonality provided tlre basis íor 13 morphoclimatic zones (Tricart and Cailleux, 19651'7972). An energ,v balance founda tion was used to provide a quantitative clinratic basis for geographic zot ality. Sr"rbsequently, three genelations of geomorpliological study rvere recognized (Biidel, 1963) in a system (see Chapter 11) introduced in Germany which became more rvidely known after a paper by Holzner and §íeaver (1965), and rvas also gfedually refined to culn-rir-rate in eigl.t climato-nrorphogenetic zones. A schernc of nine nlorphosenetic systems was introduced in the USA (Peltier, 1950; 197-5), cach clistinguished by a characteristic assemblage of geomorphic pIoccs5es, stimrrlating interest il-t periglacial environments in particular It might appear that matelials have attracted less attenti