cycle of erosion is fundamental in geomorphology. davis model is classic but upsc also asks about alternatives. comparative notes covering all three major models.
davis geographical cycle:
proposed by william morris davis. also called normal cycle of erosion.
stages:
youth: steep gradients active downcutting v shaped valleys waterfalls rapids. high relief.
maturity: lateral erosion begins. valleys widen. tributaries develop. maximum topographic complexity.
old age: gentle gradients meandering rivers. low relief. peneplain formation. monadnocks remain as residual hills.
assumptions:
rapid tectonic uplift followed by stability. erosion during stable period. time is crucial variable. humid climate assumed.
criticism:
requires long tectonic stability rarely found. humid climate bias. peneplain formation never actually observed completed. ignores climate variations.
penck model of landscape evolution:
walther penck proposed alternative. focused on relationship between uplift and erosion rates.
key concept:
landscape reflects balance between tectonic uplift rate and denudation rate.
waxing development: uplift faster than erosion. convex slopes develop. steepening landscape.
waning development: erosion faster than uplift. concave slopes develop. landscape lowering.
advantage over davis:
does not require tectonic stability. continuous interplay of forces. more realistic for tectonically active regions.
disadvantage:
difficult to quantify uplift and erosion rates. less practical for field application.
king pediplanation model:
lester king focused on arid and semi arid landscapes. especially africa.
key concept:
parallel retreat of slopes. escarpments retreat maintaining their angle. pediments form at base. pediments coalesce to form pediplain.
stages:
escarpment formation. parallel retreat. pediment extension. pediplain development.
application:
explains african landscape evolution better than davis model. also useful for indian peninsular region.
comparison table:
davis: slope decline sequential stages peneplain end product
penck: uplift erosion balance continuous process no specific end form
king: slope retreat parallel process pediplain end product
upsc optional relevance:
paper 1 geomorphology section. comparison question very common pattern. also asked as evaluate davis model or critically examine cycle of erosion.
diagram requirements:
slope profiles for each stage. comparative diagrams essential for full marks. practice drawing youth maturity old age cross sections.
recent research:
modern geomorphology uses quantitative approaches. landscape evolution models now computerized. davis model considered historical importance but not practically applied.
Discussion(2)