Morphogenetic Regions

Regions- formal and functional are concepts that geographers have used to categorise the different areas of the world based on some unifying element. Both regions have been profusely used in physical and human geography, such as natural regions, climatic regions, linguistic regions, cultural regions etc. Morphogenetic regions are those in which the climatic phenomena give a pronounced distinction to the landforms and the geomorphic processes.

Regions

Region is a dynamic concept which has been described differently by geographers based on distinct characteristics. It is a homogeneous area on the earth’s surface marked with similar characteristics making it different from other areas for geographers. The concept of region is very useful as it helps in organizing different attributes accordingly and thus makes a vast amount of information simple so that it can be understood based on different spatial perspectives.

Famous French geographer Vidal de la Blache called areas with similar physical and cultural characteristics as ‘Pays’. A widely accepted definition of the region is “an area having the homogeneity of physical and cultural phenomena”. The basic idea of classification of the region is to show the homogeneity of geographical features making it distinct individually based on different features like vegetation, soils, climatic factors, structure, industrial resource regions, agricultural regions, settlements and population distribution. Thus, through regions, geographers attempt to show distinct individuality with unique characteristics of the region. The concept of a region can be universally applied and divided into two main categories – Formal Region and Functional region.

Formal Region

It is an area which has one or more characteristics in common. These shared characteristics can be at the physical level (topography, soil, climate, vegetation, relief); at the cultural level (language, religion, and ethnicity); and at organizational phenomena (socio-economic institutions).

The best example of a formal region is continents like Europe, Asia, and Africa have distinct boundaries. Another example is the equatorial region, tropical region, temperate region, and tundra region, which are characterized so based on temperature and rainfall. The morphogenetic region is also an example of a formal region where it is classified based on temperature and precipitation.

Functional Region

Functional region is spatial systems which are defined based on interactions and connections, giving them a dynamic and organizational basis. It is organized so that it functions as a single unit in terms of political, social and economic aspects. These are the focal regions connected by various systems such as transportation, communication and economic activities.

‘City region’ is the best concept of functional region. The city region is “an area of interrelated activities, kindred interests and common organizations, brought into being through the medium of the routes which bind it to the urban Centers”. NCT of Delhi is an example of a functional region as it serves as the focal point of all the economic, political and social activities catering to the surrounding region.

Geomorphology and Climatic Geomorphology

While it is important to contextualise formal and functional regions and understand the nature of the morphogenetic region, it is pertinent to relate to themes of geomorphology and climatic geomorphology differently.

Geomorphology is derived from geo-earth, morpho-form and logis- discourse. Geomorphology is the science which deals with the study of the origin and development of landforms like sand dunes, caves, hills and valleys and how all the landforms contribute to their landscape formation. The core elements of the subjects include evolution, change and analysis of landforms.

Geomorphological studies include the quantitative analysis of landform shapes, the monitoring of surface and near-surface processes like running water, ice, and wind that shape landforms, and the characterization of landform changes that occur in response to factors such as tectonic and volcanic activity, climate and sea level change, and human activities.

Davisian concept (1899) of “Landform as a function of structure, process and time” provided the foundation basis of the geomorphic study of landforms from the structural, geomorphologic point of view and to understand the erosion cycle.

The various denudational process taking place on the earth’s surface is affected by climatic factors. Taking the importance of climate in sculpturing the landscape, a branch of investigation of geomorphology known as climatic geomorphology has evolved.

Climatic geomorphology can be defined as the discipline that identifies climatic factors such as intensity, frequency and duration of precipitation, frost intensity, direction and wind power, and it explains the development of landscapes under different climatic conditions.

Earlier, the study of geomorphology focused on analysing the sequence and nature of geomorphic events involved in the present configuration of the Earth’s surface through geological time. Some geographers called this approach historical geomorphology. The study of the working processes at a smaller level and the analysis of landform variability have resulted in the quantitative or processes geomorphology.

Morphogenetic Regions

Morphogenetic region is a theoretical concept propounded by various geomorphologists to relate landforms and geomorphic processes with climate. This concept was first proposed by German geographer Julius Budel in 1945. This concept asserts that under a certain set of climatic circumstances, different sets of geomorphic processes predominate and produce distinct topographic features. This theory assumes that rock type resistant to erosion depends on the climatic conditions to which it is subjected. Now, it becomes clear by analyzing different factors that this landform features result from the interaction of rock type, physical processes and more predominantly climatic phenomena.

In general, morphogenetic regions are large areas with distinct geomorphic processes (like weathering, frost action, mass movements and wind action) which operate and tend towards a state of morphoclimatic equilibrium. It is an area where similar processes, particularly climate, shape landforms. In this, the distinctive morphogenesis of an area is investigated. According to Chorley et al. (1984), ‘‘the extent to which different climatic regimes are capable of exerting direct and indirect influences on geomorphic processes and thereby of generating different ‘morphogenetic’ landform assemblages’’. For this, sometimes climate-morphogenetic regions are also used. Penck, in 1909 used Arid, Humid and Nival as the name for zones with distinct climates, hydrology and geomorphology. Earlier, he recognized that these regions have shifted their position during the Pleistocene’s warm and cold periods; later, in 1913, he introduced the term ‘pluvial’.

According to Peltier (1950, p. 217), morphogenetic regions are those geomorphic areas characterized by climatic regimes “within which the intensity and relative significance of the various geomorphic processes are … essentially uniform.” They are defined broadly regarding temperature versus rainfall, and he identified nine types of such regions. Peltier also defined the main geomorphic agents, showing climatic fields of weaker or stronger action.

“The concept of a morphogenetic region is that under a certain set of climatic conditions, particular geomorphic processes will predominate and hence will give to the landscape of a region characteristics that will set it off from those of other areas developed under different climatic conditions” (Thornbury,1954, pp. 60-63). Morphogenetic regions are conceptual tools by which a geomorphologist relate climatic phenomena, process, landforms and regions.

The morphogenetic concept does not directly identify those features of the landscape which replicate factors other than process and climate. Thus, landforms whose origin is largely tectonic, lithological, structural, or volcanic are not considered under morphogenetic classification but are discussed under the general heading of morpho-structure. Also excluded are landforms that reflect processes relatively independent of climate, like wave-produced features. This type of classification takes into account regions in which a distinctive complex of erosional, transformational and depositional processes is responsible for landform development. The system approach emphasizing process measurement and the relation between process and form has successfully identified many features of the landscape that appear to show a consistent relationship between inputs and outputs or form.

Morphogenetic processes that form the landform from earth materials are classified into endogenetic and exogenetic. The endogenetic processes are energy forces which act within the earth’s crust, including crustal or non-isostatic warping within the mantle, causing earthquakes, folding, faulting, metamorphism etc. The exogenetic processes are phenomena outside the earth’s crust, covering erosion, weathering, and other surface processes under climatic influence. The duration, frequency and effectiveness of geomorphic processes record wide distinguishing features in the long-time unit reflected on landforms. The maturity and chronological sequence of landforms as well as the depositional pattern, help the reconstruction of climatic changes. However, while analysing the sequence of fluvial or slope deposits, it may be concluded that the deposition represents only a small fragment of time. On the contrary, much longer time intervals are reflected in a hiatus or erosional surfaces (Starkcl, 1977).

Peltier, 1950 produced a process-based classification of so-called ‘morphogenetic regions’ based on an analysis of the temperature and precipitation ranges within which six major geomorphic processes operate. Peltier identified the following nine regions.

1. Glacial– average annual temperature range 0–20°F; average annual rainfall range 0-115 cm. Dominant processes- glacial erosion, wind action and nivation.
2. Periglacial– average annual temperature range 5–30°F; average annual rainfall range 10– 140 cm. Dominant processes- strong mass movements, moderate to strong wind, and weak fluvial action.
   Peltier identifies a distinct periglacial cycle in cold, humid, subarctic regions associated with the production of three coexisting erosion surfaces:
   (a) A surface of downwasting produced by congeliturbation
   (b) A surface of lateral planation produced where the water table and the zone of frequent nivation coincide
   (c) A stream-graded or aggraded surface.
   Davis regarded periglacial action as a climatic accident, but Peltier followed Troll in believing its characteristics to be sufficiently significant and persistent to be separately categorized. Peltier considered each cycle (including the periglacial (Troll 1948), to be normal within its regime and an accident only when one morpho-climate temporarily encroaches on another regime. However, The question remained as to whether periglacial conditions have persisted long enough in any one locality to produce a distinctive set of landforms distinct from ‘mere embroidery’ of the landscape.
3. Boreal– average annual temperature range 15–38°F; average annual rainfall range 10–60 inches. Dominant processes- moderate frost action, moderate to slight wind action and moderate fluvial action. Essentially Köppen’s Dfc region.
4. Maritime– average annual temperature range 35–70°F; average annual rainfall range 50– 75 inches. Dominant processes- strong mass movements and moderate to strong fluvial action. It has been pointed out that Peltier’s regions 3 and 4 have no dominant geomorphic characteristics to distinguish them from regions 2 and 6.
5. Selva– average annual temperature range 60–85°F; average annual rainfall range 55–90 inches. Dominant processes- strong mass movements, slight slope wash and no wind action. This humid tropical morpho-climate was based on the work of Bornhardt, Sapper, Freise and Cotton.
6. Moderate– average annual temperature range 35–85°F; average annual rainfall range 35– 60 inches. Dominant processes- strong fluvial action, moderate mass movements, slight frost action and no significant wind action. This approximated to Davis’ (1899H) ‘normal’ cycle.
7. Savanna– average annual temperature range 10–85°F; average annual rainfall range 25– 50 inches. Dominant processes- strong to weak fluvial action and moderate wind action (Cotton 1942, 1961).
8. Semi-arid average annual temperature range 35–85°F; average annual rainfall range 10–25 inches. Dominant processes- strong wind action and moderate to strong fluvial processes. Includes the dry continental regions (Cotton 1942).
9. Arid– average annual temperature range 55–85°F; average annual rainfall range 0–15 inches. Dominant processes- strong wind action and slight fluvial and mass movement processes (Davis, 1905).

Morpho-Climatic Zones

In 1948, German geographer Budel introduced the system of climatic geomorphology (Das System der klimatischen). He has given a descriptive analysis of the distinctive processes associated with each morphoclimatic zone. The most important aspect was the interrelationship of the processes in one zone, that is, the work of the river is dependent on the relief of the area, and further, the precipitation controls the amount and time of discharge. The load transported by river streams generally depends on slopes and creeks.

A simplified morphoclimatic classification proposed by Köppen is based primarily on the regional classification of vegetative significance with the combination of temperature and precipitation, giving climatic expression to a geomorphological significant process. Based on this, he identified 6 regions designated by capital letters – A, B, C, D, E and H. These major regions have been subclassified using lowercase alphabets based on precipitation (s, w, f, m) and temperature (a, b, c). These were grouped to generate eight morphoclimatic regions, which fall into two groups wherein the major geomorphic processes are either non-seasonal or seasonal.

A). Non-seasonal category includes the glacial, arid and humid tropical. These have non-seasonal processes normally having low average erosion rates, highly infrequent and episodic erosional activity like desert rainstorms, glacial surges and slope mass failures and a tendency for the location of their cores to persist latitudinally (at 90° 25° and 0°, respectively) during climatic changes, even if the climatic type is completely obliterated on occasions.

B). Seasonal group includes tropical wet-dry, semi-arid, dry continental, humid mid-latitude and periglacial regions. These have processes which are more specifically seasonal in their operation, with places having high average erosion rates; erosional activity though episodic, shows some consistency over a period of years; and a tendency for considerable changes of their size and location accompanying global climatic changes. Such regions are divided into two groups:

• Warmer climates (tropical wet-dry and semi-arid), where geomorphic processes differ most significantly in terms of the length of the wet season.
• Cooler climates (dry continental, humid mid-latitude and periglacial) whose geomorphic processes differ mainly in summer temperatures, as well as with some regard to precipitation amounts.

Using the classic Davisian cyclic basis, C. A. Cotton (1942) identified six morphoclimatic regions, including four main types and two transition types, each with characteristic mature landforms.

1. Normal (main)- applying to humid temperate landforms.
2. Glacial (main)- includes the Davisian glacial cycle but excludes periglacial landforms.
3. Humid tropical (transitional)
4. Arid (main)- landforms dominated by interior drainages like bajada and pediment extension, basin capture, slope retreat and the replacement of desert mountains by low domes. Fluvial (sheet flood and stream flood) processes dominate but are increasingly assisted through time by Aeolian processes. A sharp break appears to exist between the hillslope (30–35° or more), on the one hand, and the pediments (5–7° in the higher parts and 3–4° in the lower ones) and the virtually flat bajadas, on the other.
5. Semi-arid (transitional)- it is difficult to distinguish from arid conditions in terms of processes but with the upper pediment slopes being steeper and breaks of slopes less abrupt. The semi-arid morphoclimatic region is much more difficult to distinguish from the arid and the savanna regions.
6. Savanna (main)- showing the flat plains and abrupt inselbergs.

A more refined morphoclimatic classification was proposed by Büdel (1944, 1948b). Underlining the intricacy of the climatic processes controlling landforms (e.g. a number of frost-thaw cycles), Büdel argues that major landforms change more slowly than climate (and are thus relics of numerous past climates) and that any attempt to link present-day climate and landforms must concentrate on those forms which are small scale and rapidly evolving. He proposed the following morphoclimatic classification involving eight terrestrial regions and ten subregions:

1. Glacier zone
2. Frost-rubble zone (Frostschuttzone)
3. Tundra zone
4. Extra-tropical (mature: in situ) soil zone (Nichttropische Ortsbödenzone)
   • (a) maritime temperate zone
   • (b) Subpolar tjäle-free (sub-polar without permafrost)
   • (c) tjäle zone (sub polar with permafrost)
   • (d) continental zone
   • (e) steppe zone
5. Mediterranean transition zone (Etesische Ubergangszone)
6. Arid-rubble zone (Trockenschuttzone)
   • (a) tropical inselberg-pediment desert zone
   • (b) extra-tropical desert zone
   • (c) high-altitude (cool) desert zone
7. Wash-plain zone (humid savanna) (Flächenspülzone)
   • (a) tropical wash-plain (sheetwash) zone
   • (b) sub-tropical wash-plain (sheetwash) zone
8. Inter-tropical mature equatorial soil zone (Innertropische Ortsbödenzone)

This type of classification created wide interest among geographers though it was criticized for many reasons. Firstly, due to its Azonal organization, a subdivision of permafrost between frost, tundra, subpolar with permafrost; Grouping of taiga and permafrost with maritime forest and steppe and lastly, the separate identification of the Mediterranean landforms.

Tricart and Cailleux (1955, 1965) proposed the following classification of morphoclimatic zones. According to them, Vegetation type is an indirect impact on climate. Under the given climatic conditions, the plant cover modifies the morphogenetic processes, but, in turn, the latter impact the ecologic conditions of the region and thus, there is an impact on vegetation.

1. The cold zone.
   • (a) Glacial
   • (b) Periglacial (later subdivided into five by Tricart).
2. The mid-latitude forest zone (affected by past climates, particularly Pleistocene, and by human activity).
   • (a) Maritime (relict Pleistocene glacial and periglacial forms survive).
   • (b) Continental (Pleistocene permafrost may survive).
   • (c) Mediterranean (relict Pleistocene periglacial forms least important)
3. The dry zone. Subdivided on the bases of:
   • (a) Water deficiency in the steppe, xerophytic bush and desert;
   • (b) Winter temperatures into cold and warm.
4. The humid tropical zone.
   • (a) Savannas, affected by earlier drier conditions, evidence of semi-arid pediplanation and of climatic changes in the form of ‘cuirasses’ (i.e. laterites, calcretes and silcretes).
   • (b) Tropical rain forests.

From these broad morphoclimatic zones, Tricart and Cailleux (1965 and 1972) developed a classification of world morphoclimatic regions in which morphoclimatic and morphogenetic (i.e. relict) influences are not clearly distinguished:

1. Glacial regions;
2. Periglacial regions with permafrost;
3. Periglacial regions without permafrost;
4. Forest on Quaternary permafrost;
5. Maritime forest zone of mid-latitudes with mild winters;
6. Maritime forest zone of mid-latitudes with severe winters;
7. Mid-latitude forest zone of Mediterranean type;
8. Semi-desert steppes:
   • (a) Semi-desert steppes with severe winters;
9. Deserts and degraded steppes without severe winters;
10. Deserts and degraded steppes with severe winters;
11. Savannas;
12. Intertropical forests;
13. Azonal mountain areas.

As per Budel(1948, 1982), the geographers have identified morphoclimatic and morphogenetic regions differently. Wilson identifies 5 regions, Peltier – 8, Flohn – 8, Köppen -11, Strahler – 14, Trewartha – 16, Thornwaite – 18. Finally, the following Table presents a broad classification of morphogenetic region that has been devised by combining the distinct climatic characteristics, the geomorphic process and nomenclature as given by Köppen.

Role of Morphogenetic Regions in Land Use Planning

Different morphogenetic parameters like climate, lithology and structure, drainage and slope have direct consequences on the choice of natural land use practices. Thus, it becomes very important to take cognizance of physical limiting parameters while opting for land use planning. But instead of this what actually happens is that physical determinant are ignored and the land use pattern are identified on the basis of economic, social and political. Thus, preceding land use planning, analyses of terrain condition must take place. Terrain evaluation comprises classification of land and creation of databank taking into account all the genetic factors which are necessary for the practical requirements of any land use planning.

Land use pattern of an area is the result of the interrelationship between the people inhabiting the area and their environment. Terrain type and environment determine the land use pattern of an area whereas land use practices itself can contribute to their change of landscape having long term manifestations.

Read More in Geomorphology

1. Earth Movements: Meaning and Types
2. Epeirogenic Earth Movements
3. Orogenic Earth Movements
4. Cymatogenic Earth Movements
5. Concept of Stress and Strain in Rocks
6. Folds in Geography
7. Fault in Geography
8. Mountain Building Process
9. Morphogenetic Regions
10. Isostasy: Concept of Airy, Pratt, Hayford & Bowie and Jolly
11. Continental Drift Theory of Alfred Lothar Wegener (1912)
12. Plate Tectonics: Assumptions, Evidences, Plate Boundaries and Features Formed
13. Volcanoes: Process, Products, Types, Landforms and Distribution
14. Earthquakes: Processes, Causes and Measurement
15. Plate Tectonics and Earthquakes
16. Composition and Structure of Earth’s Interior
17. Artificial Sources to Study Earth’s Interior
18. Natural Sources to Study Earth’s Interior
19. Internal Structure of Earth
20. Chemical Composition and Layering of Earth
21. Weathering: Definition and Types
22. Mass Wasting: Concept, Factors and Types
23. Models of Slope Development: Davis, Penck, King, Wood and Strahler
24. Davis Model of Cycle of Erosion
25. Penck’s Model of Slope Development
26. King’s Model of Slope Development
27. Alan Wood’s Model of Slope Evolution
28. Strahler’s Model of Slope Development
29. Development of Slope
30. Elements of Slope
31. Interruptions to Normal Cycle of Erosion
32. Channel Morphology and Classification
33. Drainage System and Drainage Pattern
34. River Capture or Stream Capture
35. Stream Channel Pattern
36. Fluvial Processes and Landforms: Erosional & Depositional
37. Delta: Definition, Formation and Types
38. Aeolian Processes and Landforms: Erosional & Depositional
39. Desertification: Definition, Problem and Prevention
40. Glacier: Definition, Types and Glaciated Areas
41. Glacial Landforms: Erosional and Depositional
42. Periglacial: Meaning, Processes and Landforms
43. Karst Landforms: Erosional and Depositional
44. Karst Cycle of Erosion
45. Coastal Processes: Waves, Tides, Currents and Winds
46. Coastal Landforms: Erosional and Depositional
47. Rocks: Types, Formation and Rock Cycle
48. Igneous Rocks: Meaning, Types and Formation
49. Sedimentary Rocks: Meaning, Types and Formation
50. Metamorphic Rocks: Types, Formation and Metamorphism
51. Morphometric Analysis of River Basins
52. Soil Erosion: Meaning, Types and Factors
53. Urban Geomorphology: Concept and Significance
54. Hydrogeomorphology: Concept, Fundamentals and Applications
55. Economic Geomorphology: Concept and Significance
56. Geomorphic Hazard- Earthquake: Concept, Causes and Measurement
57. Geomorphic Hazard- Tsunami: Meaning and Causes
58. Geomorphic Hazard- Landslides: Concept, Types and Causes
59. Geomorphic Hazard- Avalanches: Definition, Types and Factors
60. Integrated Coastal Zone Management: Concept, Objectives, Principles and Issues
61. Watershed: Definition, Delineation and Characteristics
62. Watershed Management: Objective, Practice and Monitoring
63. Applied Geomorphology: Concept and Applications