A morphogenetic region is a theoretical zone that geomorphologists use to link climate, geomorphic processes, and landforms. The underlying idea is that each climatic regime favours certain geomorphic processes, and these in turn give rise to a distinctive landscape. Supporters of the concept argue that climate matters more than rock type in shaping landforms, since how well a rock resists erosion depends on the climate acting upon it. Current understanding, however, holds that landforms arise from the combined influence of climate, rock type, and physical processes. The idea is usually traced to German-speaking geomorphologists in the early-to-mid 20th century, notably Julius Büdel (climato-genetic geomorphology), with earlier groundwork by W.M. Davis’s critics, and later work by Louis Peltier, Jean Tricart, and André Cailleux. Peltier’s 1950 model of periglacial morphogenetic regions is a classic example.
Davis’s Cycle of Erosion (youth, maturity, old age) emphasized time and stage over climate. Climatic geomorphologists argued that this overlooked a basic fact: weathering, erosion, and transport work differently under different climates. Frost shattering, chemical weathering, and wind action don’t produce the same landforms, so the climate-process-landform link deserved to be the organizing principle.
Typical Geomorphogenetic Regions
01. Peltier’s morphogenetic regions (1950)
Louis C. Peltier presented his scheme in 1950 in the Annals of the Association of American Geographers, in a paper on the geographic cycle in periglacial regions. It was an attempt to put climatic geomorphology on a quantitative footing. Instead of describing regions in words, he defined them using mean annual temperature and mean annual precipitation, and plotted them on a temperature-rainfall diagram.
1. Glacial Region
Climate: Very cold, with low precipitation falling mostly as snow.
Processes: Glacial erosion and deposition, with intense frost action.
Landforms: Cirques, arêtes, horns, U-shaped valleys, and fjords from erosion. Moraines, drumlins, eskers, and outwash plains from deposition.
2. Periglacial Region
Climate: Cold, with permafrost and low to moderate precipitation.
Processes: Frost shattering, freeze-thaw, solifluction, and nivation, with very little chemical weathering.
Landforms: Patterned ground, pingos, block fields, tors, asymmetric valleys, and thermokarst.
3. Boreal Region
Climate: Cold winters, short cool summers, moderate precipitation.
Processes: Moderate frost action and mass wasting, slight chemical weathering. Coniferous forest stabilizes the surface.
Landforms: Gentle, rounded slopes, bogs, muskeg, and lakes, with much relief inherited from past glaciation.
4. Maritime Region
Climate: Cool and humid, with a small temperature range.
Processes: Moderate chemical weathering, mass wasting, and fluvial action, with little frost.
Landforms: Smooth, soil-covered slopes, graded valleys, and slumps and earthflows on wet slopes.
5. Moderate (Humid Mid-Latitude) Region
Climate: Mild and humid, with distinct seasons.
Processes: Moderate weathering, slope wash, and dominant fluvial action.
Landforms: Graded river profiles, floodplains, terraces, and convex-concave hillslopes with thick soil cover.
6. Selva (Tropical Rainforest) Region
Climate: Hot and very wet throughout the year.
Processes: Very strong chemical weathering and mass wasting, with almost no frost or wind action.
Landforms: Deep saprolite, rounded soil-mantled hills, narrow deeply cut valleys, and landslide scars.
7. Savanna Region
Climate: Hot, with distinct wet and dry seasons.
Processes: Seasonal sheet wash and fluvial action, with chemical weathering in the wet season.
Landforms: Pediplains, inselbergs, bornhardts, broad shallow valleys, and laterite crusts.
8. Semiarid Region
Climate: Warm to hot, with low and erratic rainfall.
Processes: Slope wash and flash floods, with moderate wind action. Sparse vegetation allows rapid runoff.
Landforms: Pediments, badlands, alluvial fans, arroyos and wadis, mesas, and buttes.
9. Arid Region
Climate: Very dry, with large daily temperature ranges.
Processes: Wind action, salt and thermal weathering, and rare but powerful runoff.
Landforms: Dunes, deflation hollows, desert pavements, yardangs, and playas.
02. Büdel’s Climatic-Geomorphological Zones (1948 onward)
Julius Büdel, a German geomorphologist, developed his scheme of climato-genetic geomorphology from the late 1940s and refined it for decades (his major synthesis, Climatic Geomorphology, appeared in German in 1977 and in English in 1982). Unlike Peltier’s quantitative diagram, Büdel’s approach was descriptive and global. He divided the Earth into zones based on the dominant geomorphic processes and the relief they produce, with particular attention to how valley incision and surface lowering (planation) operate in each. He also stressed that present landforms often include relict forms from past climates.
1. Zone of permanent frost and ice (polar)
- Process: Glacial erosion and frost weathering.
- Meaning: Ice sheets and glaciers scrape and carve the land, while frost cracks rock apart.
- Typical forms: Cirques, U-shaped valleys, fjords, moraines.
2. Zone of valley formation (tundra/periglacial)
- Process: Solifluction and frost-driven denudation, with fluvial erosion by meltwater.
- Meaning: Solifluction is the slow downslope flow of thawed, waterlogged soil over frozen ground. Denudation is the general lowering of land by weathering and removal. In summer, meltwater streams also cut valleys.
- Typical forms: Patterned ground, block fields, smooth lobed slopes, asymmetric valleys.
3. Extratropical valley-forming zone (temperate)
- Process: Linear fluvial incision.
- Meaning: “Linear” means erosion along lines, that is, river channels cutting downward. This creates V-shaped valleys. Vegetation protects the slopes, so rivers do most of the work rather than surface wash.
- Typical forms: V-shaped valleys, river terraces, floodplains.
4. Subtropical zone of pediplanation (arid and semi-arid margins)
- Process: Broad surfaces and sheetwash.
- Meaning: Pediplanation is the formation of wide, gently sloping rock surfaces (pediments) as hillslopes retreat backward. Sheetwash is thin, unchanneled water flowing over bare ground after rain. Sparse vegetation lets it strip the surface.
- Typical forms: Pediments, pediplains, alluvial fans, inselbergs.
5. Tropical zone of excessive planation
- Process: Deep weathering and wide planation surfaces, including etchplains, plus inselbergs.
- Meaning: Heat and moisture rot the rock to great depths. When this weathered layer is stripped away, a very flat surface remains. An etchplain is a surface “etched” out by removing deeply weathered rock. Inselbergs are isolated rock hills left standing above the plain because they resisted weathering.
- Typical forms: Etchplains, inselbergs, bornhardts, deep weathering profiles.