An antecedent stream is a stream that maintains its original course and pattern despite the changes in underlying rock topography. A stream with a
dendritic drainage pattern, for example, can be subject to slow tectonic uplift. However, as the uplift occurs, the stream erodes through the rising ridge to form a steep-walled
gorge. The stream thus keeps its dendritic pattern even though it flows over a landscape that will normally produce a
trellis drainage pattern.
[Grotzinger, J. & Jordan, T.H. 2006. Understanding Earth, 5th ed., Freeman, New York ]
A superimposed stream is a
stream that forms over horizontal beds that overlie folded and faulted rock with varying resistance. Having cut down through the horizontal beds, the stream retains its course and pattern as it proceeds to erode the underlying rocks despite their different character. The stream erodes a gorge in the resistant bed and continues its flow as before.
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Examples
* Many Himalayan rivers are good examples of antecedent origin. These rivers originated well before the Himalayan region was uplifted. The rivers Indus, Brahmaputra
The Brahmaputra is a trans-boundary river which flows through Tibet, northeast India, and Bangladesh. It is also known as the Yarlung Tsangpo in Tibetan, the Siang/Dihang River in Arunachali, Luit in Assamese, and Jamuna River in Bangla. I ...
, Sutlej, Kosi and Subansiri originated on the Tibetan side and now traverse the existing mountain ranges, cutting deep gorges.
* The Colorado River
The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid watershed that encompasses parts of seven U.S. s ...
cut the Grand Canyon as the Colorado Plateau rose between 5 and 2.5 million years ago. Paradox Valley
Paradox Valley is a basin located in Montrose County in the U.S. state of Colorado. The dry, sparsely populated valley is named after the apparently paradoxical course of the Dolores River—instead of flowing down the length of the valley, t ...
is another good example in the Colorado Plateau.
* Devil's Gate in Wyoming is a remarkable display of an antecedent stream. A 100-meter slot is cut through a granite ridge which would have missed the ridge completely had the river flowed just a kilometer to the south.
* The Meuse
The Meuse ( , , , ; wa, Moûze ) or Maas ( , ; li, Maos or ) is a major European river, rising in France and flowing through Belgium and the Netherlands before draining into the North Sea from the Rhine–Meuse–Scheldt delta. It has a t ...
still flows south-north from France to Belgium through the Ardennes which were elevated after the river had assumed that course.
See also
* Canyon
* Water gap
A water gap is a gap that flowing water has carved through a mountain range or mountain ridge and that still carries water today. Such gaps that no longer carry water currents are called wind gaps. Water gaps and wind gaps often offer a prac ...
* Wind gap
A wind gap (or air gap) is a gap through which a waterway once flowed that is now dry as a result of stream capture. A water gap is a similar feature, but one in which a waterway still flows. Water gaps and wind gaps often provide routes which ...
References
{{Rivers, streams and springs
Hydrology
Geomorphology