Penck's Cycle of Erosion | Treppen Concept | Geomorphology| Dr. Krishnanand

Penck’s Cycle of Erosion and the Treppen Concept

Dr. Krishnanand explains Walther Penck’s model of landscape development and contrasts it with W. M. Davis’s cycle of erosion.

Penck’s central idea

• Penck’s model is also called the morphological system or morphological analysis of landscape development.
• It is associated with the Treppen concept—German for “staircase”—because valley sides may form a series of step-like surfaces.
• Unlike Davis’s model, Penck’s explanation gives importance to both:
  • Endogenetic forces, especially tectonic uplift.
  • Exogenetic processes, such as weathering, erosion, mass wasting, transport, and deposition.
• Landforms reflect the relationship—or competition—between the rate and intensity of uplift and the rate of degradation and material removal. Uplift and erosion can occur at the same time.
• Penck described landscape development in terms of phases, rather than Davis’s sequential stages. His model remains time-dependent, but the form of the landscape depends on how uplift and erosion interact over time.

The three phases of development

Penck’s cycle begins with regional uplift, described in the lecture as up-doming, and proceeds through three main phases:

1. Waxing phase

   • Uplift accelerates.
   • The land rises while erosion is also active.
   • The initial surface is called the Primärrumpf, or primary surface. The subtitles render the term as “primal rump.”
   • The lecture notes that areas between streams—the interfluves—rise as uplift proceeds, with little strong undercutting at first.

2. Phase of uniform development

This phase has three subphases—A, B, and C—representing a changing balance between uplift and river downcutting:

  - **A:** Uplift exceeds downcutting; the landscape continues to rise.
  - **B:** Uplift and downcutting are approximately balanced, producing a relatively steady profile.
  - **C:** Downcutting becomes stronger, and relief begins to decline.

1. Waning phase
   • Landforms progressively decline as erosion and lowering gain influence.
   • Valleys widen, and parallel retreat of valley-side slopes continues: slopes move backward while broadly retaining their form.
   • The lecture gives German terms for slope forms: Boschungen for steeper slopes and Haldenhang for gentler, lower-angle slopes. The subtitles’ spellings may be approximate.
   • The cycle’s later surface is called the Endrumpf (“end rump” in the subtitles).
   • Residual rocky hills, or inselbergs, may remain on this surface.

Comparison with Davis

• Uplift: Davis’s model emphasizes a sudden uplift followed by landscape development; Penck emphasizes gradual uplift and its changing relationship with erosion.
• Main explanation: Davis describes landforms as a function of structure, process, and stage. Penck emphasizes the balance between endogenetic activity and exogenetic denudation.
• Geographic applicability: The lecture presents Davis’s fluvial cycle as most applicable to humid and subhumid regions, while Penck’s approach can account for a wider range of settings, including semiarid and tropical regions.
• End product: Davis’s cycle leads to a broad, subdued peneplain, with residual hills called monadnocks. Penck’s cycle ends in an Endrumpf, which may retain residual hills identified as inselbergs.

Speakers and sources featured

• Speaker: Dr. Krishnanand, presenter of TheGeoecologist.
• Scholars and theories discussed: Walther Penck and W. M. Davis.