Examkin

Question

Difficulty: EasyLandform Evolution by Running Water and Underground Water

Arrange the following stages in the formation of an oxbow lake in the correct sequential order from first to last.

  1. 1The river forms a pronounced meander loop with a narrow neck.
  2. 2Continuous lateral erosion on the outer bends and deposition on the inner bends further narrow the neck of the meander.
  3. 3The river cuts straight through the narrow neck during a period of high discharge or flood.
  4. 4Sediment deposition seals off both ends of the old meander loop, leaving an isolated crescent-shaped body of standing water.

Answer

The correct sequence of oxbow lake formation begins with the river forming a pronounced meander loop, followed by continuous erosion and deposition narrowing the neck. The river then cuts straight through the neck during a flood, and finally deposition seals off the abandoned loop to form an oxbow lake.
The correct order follows the progressive geomorphic stages of oxbow lake development: initial meander development with a narrow neck, neck narrowing through lateral erosion and deposition, sudden neck cut-off during a flood event, and final isolation of the crescent lake by alluvial deposition at the entrance and exit of the abandoned loop.

Step-by-Step Solution

1
Identify the initial channel shape
Establish that a meander loop with a narrow neck must exist prior to cut-off.
An oxbow lake can only form from a pre-existing river meander loop in its middle or lower course.
2
Trace the process of meander neck narrowing
Recognize that lateral erosion on hydraulic cut-banks and deposition on slip-off slopes narrow the neck.
Helicoidal flow concentrates energy on the outer banks, bringing the neck ends closer together over time.
3
Identify the breach event
Determine that flood conditions cause the river to cut directly through the neck.
High discharge provides sufficient hydraulic force to carve a new, straight channel along the path of maximum gradient.
4
Conclude with channel abandonment and isolation
Note that alluvium deposition blocks the old meander entrances.
Slower water current at the cut-off entry and exit points encourages deposition, leaving behind a cutoff lake.

Key Concept

Fluvial meander evolution and cut-off mechanisms leading to oxbow lake formation
Rate this question

Topics

Landform Evolution by Running Water and Underground Water

More questions from this topic