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
A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tend ...
. 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
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...
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, 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 () is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and in northern Mexico. The river, the List of longest rivers of the United States (by main stem), 5th longest in the United St ...
cut the Grand Canyon
The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is long, up to wide and attains a depth of over a mile ().
The canyon and adjacent rim are contained within Grand Canyon Nati ...
as the Colorado Plateau rose between 5 and 2.5 million years ago. Paradox Valley 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 or Maas 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 total length of .
History
From 1301, the upper ...
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
* Wind gap
References
{{Rivers, streams and springs
Hydrology
Geomorphology