9 Explain the formation of an oxbow lake in as much detail as possible. 10 Please define the following terms: headwaters, tributary, main channel, and delta/mouth.
Q. Explain the formation of an oxbow lake in as much detail as possible.
Answer: During the life of the river while flowing from head to mouth, the rivers are capable of exerting greatly modifying influence its topography through which the rivers are actually flowing. This modification in the topography by the rivers is known as the geological work of the rivers. The modification takes place from head to mouth of the river profile by different processes like abrasion, attrition, erosion, deposition, corrosion etc. The topography of the rivers is modified by various erosional and depositional features along the river profile. The various erosional features developed by the rivers are potholes, river valleys, gorges, canyons, waterfalls, etc. and various depositional features are natural levees, deltas, alluvial fand and cones.
There are some other features developed in the profile of the river like river meandering, oxbow lakes, incised meanders etc where both the erosional and deviational processes take place for their formation. As the rivers reach in the middle and lower courses, they gain more waters and more energy. Lateral erosion and deposition along opposite banks become almost concurrent. With the passage of time, when the river flows over flatter land, they develop a curved, zigzag path acquiring a loop shaped course, it is said to have developed meandering.
In the advanced stages of meandering of the rivers, due to the erosion on the outside of a bend and deposition on the opposite side, the shape of a meander slowly gets modified. Slowly the erosion process narrows the neck of the land, and the process gets continues and in this way the meanders become very close to each other. During the high-water times, when the streams acquire good volume of waters, the rivers have the tendency to cut the neck, and flow straight and shorter route. The stream starts flowing straight in the limited stretches, therefor leaving behind the loop or lopes on the sides completely detached or slightly connected. These isolated curved or loop shaped areas of the rivers, are called the ox bow lakes. Deposition will occur to cut off the original meander, leaving a horseshoe-shaped oxbow lake. Oxbow lakes mostly form in flat, low-lying plains of the rivers.
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