A Fully Scientific Explanation of Why All Rivers on Earth are Meandering.
Excluding artificial rivers and lakes, it can be affirmed that there is no river system in the world that flows in a straight line. If you don’t believe it, you can verify it yourself using Google’s Google Earth application.
A straight line is the shortest path, yet rivers seem to make things difficult for themselves by continuously meandering over thousands of kilometers. The question here is: Why?
A river system in Alaska.
No river flows in a straight line, but to meander takes a long time.
The curvature of rivers results from a combination of various natural factors.
Water always flows downhill, but that slope may not be straight. Even if the watercourse is initially straight, over time, the river will still bend. The curvature of rivers arises from a combination of many natural factors.
Imagine this: a beaver suddenly appears and “burrows” into one bank of the river to make a den. Just a small hole, but it inadvertently weakens the soil on that riverbank.
A beaver “burrows” into one bank of the river to make a den.
Water will gradually flow into the hole at an increasing speed due to the eroded soil, simultaneously causing the flow on the opposite bank to weaken. That slow-moving water carries soil and sand, depositing it on the other bank. Over time, the previously straight stretch of river becomes literally curved.
Over time, the previously straight stretch of river becomes literally curved.
Of course, the beaver is just a fun example. In reality, many factors in nature can bend a river without the need for a beaver to dig in the ground.
From a scientific perspective, the reason rivers do not flow straight but meander is due to two main factors: topography and the Coriolis force.
- Topographical factors are easy to understand. Rivers tend to flow from higher terrain to lower terrain; in rugged areas, rivers will meander.
- The Coriolis force is a consequence of the Earth’s rotation.
As the Earth rotates on its axis, every location at different latitudes on the Earth’s surface (except the poles) has different velocities and moves from west to east. Therefore, objects moving on Earth will be deflected from their original direction. The Coriolis force significantly affects the direction of moving air masses, ocean currents, rivers, and even projectiles. Thus, we observe the phenomenon of meandering rivers, with one bank eroding while the other builds up.
At the onset of a river’s formation, the riverbed is often not flat. In places where the river flows, for various reasons, the flow speed on the left and right sides is not completely equal. One bank may erode a little, while a tree may be lost on another, and in another area, additional water flows in from outside…
These phenomena can cause the flow speed of the river to either increase or decrease at certain points. Concurrently, the materials on either bank also differ; some areas are easily eroded, while others are quite solid. All of these factors contribute to the winding, meandering nature of the riverbed.
Bending a section of the river means changing the flow direction of the water. The altered water flow creates a force acting on the riverbank soil, increasing erosion, and eventually, the remaining sections also gradually bend according to a natural law.
Bending a section of the river means changing the flow direction of the water.
Sections of rivers with larger flow rates will have longer distances between bends. However, an interesting point about all rivers in the world is that the length between an S-shaped bend will equal six times the width of the two riverbanks. In other words, a short section of river resembles a miniature version of a larger river segment.
A short section of river.
Will be a replica of larger river segments.
This curving process will continue over time. And if there are no obstacles (like boulders or mountains), there will come a time when two meandering sections of the river will meet.
At that point, the river will flow straight again, leaving behind a past of “curvature.” The “past” is known as an oxbow lake.
The formation process of an oxbow lake.
An oxbow lake can be considered a characteristic feature indicating the existence of a nearby river. And did you know that Mars also has traces of oxbow lakes, suggesting that the Red Planet once housed many oceans and a rich system of rivers?
Mars also has…
