![]() ![]() Various authors have used an entrenched river as evidence of tectonic movement in the past, and in this way they have proven the significant role of tectonic uplifts in the formation of an entrenched river. Although it is very difficult to offer detailed information of past tectonic activity, the basic temporal and spatial scale can show evidence of how this movement leads to the formation of an entrenched river. Studies show that tectonic movement, particularly movement associated with uplift, can influence spatial patterns of erosion and sedimentation. River rejuvenation increases the power of the flowing water and, therefore, the process of erosion is accelerated. Moreover, the process of river rejuvenation can also be the cause of river entrenchment, especially when the process has occurred due to tectonic uplift. It can also be caused by increased level of downcutting or a collapse of moraine-dammed lake downstream, or capture of the river by another river. Causes Īs observed above, an entrenched river can be caused by either tectonic uplift in the area or when the lowering of the sea level occurs. However, more detailed studies have shown the development of ingrown meanders versus entrenched meanders depends on a complex mixture of factors such as bedrock lithology, tectonic activity, and climate. This leads to symmetrical valleys with a gorge-like appearance. In addition, it was also argued for a long time that an entrenched meander forms when there is a rapid incision of the river bed such that the river does not have the opportunity to erode the lateral side. For a long time, it was argued that ingrown meander occurs when downcutting process is slow and the river can cause lateral erosion, leading to an asymmetric valley. They are commonly classified as either an ingrown meander or an entrenched meander. The meanders that form part of either an entrenched river or meander valley are most commonly known as incised meanders. General, nongeneric terminology for either a river or stream that flows in a narrow trench or valley, for which evidence of a preexisting plain or relatively level upland can be either absent or present is either valley meander or meander valley with the latter term being preferred in literature. The down-cutting of the river system could be the result not only of tectonic uplift but also of other factors such as river piracy, decrease of load, increase of runoff, extension of the drainage basin, or change in base level such as a fall in sea level. In the case of an entrenched stream or river, it is often presumed that the watercourse has inherited its course by cutting down into bedrock from a pre-existing plain with little modification of the original course. They widen and deepen over time and can be found as deep gorges or canyons in hard rock. The exception is that entrenched meanders are formed during the upliftment of land where river is young. Such meanders are called incised or entrenched meanders. ![]() Meandering is the feature of the middle and final course of the river.īut very deep and wide meanders can also be found cutting hard rocks. ![]() Meanders form where gradient is very gentle, for example in floodplain and delta. Entrenched meanders of the Virgin River at the upper end of Zion Canyon, Zion National Park, Utah.Īn entrenched river, or entrenched stream is a river or stream that flows in a narrow trench or valley cut into a plain or relatively level upland.īecause of lateral erosion streams flowing over gentle slopes over a time develops meandering (snake like pattern) course. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |