Base level

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Lowest limit for erosion processes

title: "Base level" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["fluvial-geomorphology", "geomorphology", "erosion"] description: "Lowest limit for erosion processes" topic_path: "geography" source: "https://en.wikipedia.org/wiki/Base_level" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Lowest limit for erosion processes ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/4/45/Desembocadura_del_Ebro.jpg" caption="Aerial picture of the [[Ebro]] river as it reaches the [[Mediterranean Sea]] by the [[Ebro Delta"] ::

In geology and geomorphology a base level is the lower limit for the vertical position of an erosion process. The modern term was introduced by John Wesley Powell in 1875. The "ultimate base level" is the surface that results from horizontal projection of the sea level under landmasses (the geoid).

There are also lesser structural base levels where erosion is delayed by resistant rocks. Base levels may be local when large landmasses are far from the sea or disconnected from it, as in the case of endorheic basins.

The height of a base level also influences the position of deltas and river terraces. A relative drop in base level can trigger re-adjustments in river profiles including knickpoint migration and abandonment of terraces leaving them "hanging". Base level fall is also known to result in progradation of deltas and river sediment at lakes or sea. If the base level falls below the continental shelf, rivers may form a plain of braided rivers until headward erosion penetrates enough inland from the shelfbreak.

When base levels are stable or rising rivers may aggrade. Rising base levels may also drown the lower courses of rivers creating rias. This happened in the Nile during the Zanclean flood when its lower course became, in a relatively short time, a large estuary extending up to 900 km inland from the Mediterranean coast.

Base level change may be related to the following factors:

  1. Sea level change
  2. Tectonic movement
  3. River capture
  4. Extensive sedimentation

References

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References

  1. Goudie, A.S.. (2004). "Base level". Routledge.
  2. (2007). "The Rise and Fall of the Davisian Cycle of Erosion: Prelude, Fugue, Coda, and Sequel". Physical Geography.
  3. Chorley, R.J. (1973). ''The History and Study of Landforms or The Development of Geomorphology. Vol. Two: The Life and Work of William Morris Davis,'' Methuen.
  4. (2013). "Stratigraphic landscape analysis, thermochronology and the episodic development of elevated, passive continental margins". [[Geological Survey of Denmark and Greenland.
  5. (2013). "Stratigraphic Landscape Analysis and geomorphological paradigms: Scandinavia as an example of Phanerozoic uplift and subsidence". [[Global and Planetary Change]].
  6. (2005). "The drainage of Africa since the Cretaceous". [[Geomorphology (journal).
  7. Spotila, James A.. (2004). "Crustal deformation". Routledge.
  8. (1994). "An Experimental Study of the Effects of Base-Level Change on Fluvial, Coastal Plain and Shelf Systems". Journal of Sedimentary Research.
  9. (2005). "Origin of the highly elevated Pyrenean peneplain". Tectonics.

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fluvial-geomorphologygeomorphologyerosion