Waterfalls are one of the most majestic nature events on the planet – a beautiful thunderous display of water and physics, whether in the form of a waterfall or a waterfall. But where do these natural creations come from?
Conventional wisdom says that waterfalls are formed by external forces, such as earthquakes, landslides, or changes in sea level that greatly alter and disrupt landscapes and river beds. But it turns out that another internally driven force may also be responsible.
A new study by researchers at the California Institute of Technology proposes a radical hypothesis about how these captivating phenomena materialize: waterfalls form like a mountain.
According to experts, one of the reasons why the formation of waterfalls has been an ancient mystery is that these water torrents evolve over geological time scales , which has made them difficult to study in a certain sense and enhancing the established narrative that waterfalls are shaped by external factors.
But just because waterfall evolution is a difficult phenomenon to study, it doesn’t mean it’s impossible to understand them.
“We propose that waterfalls can form autogenously”, explain the authors in the journal Nature that publishes the work; “which means that waterfalls can form through internal feedbacks between water flow, sediment transport and bedrock incision, in the absence of external disturbances or lithological controls.”
Laboratory simulation
To test their idea, the researchers built a mini-river inside their lab: a 7.3-meter-long channel, made from a polyurethane foam “synthetic bedrock,” and tilted it to almost one degree. They placed small gravel pebbles in the channel to represent the natural rocky sediment, and then they ran a constant discharge of water through their virtual waterfall, letting nature take its course.
Within hours, the constant flow of water and rock began to erode the river bed in soft foam, and not evenly.
“Along the riverbed, variations in decimetry from erosion created repeated convex bedrock ridges and concave depressions, which grew in amplitude to form cyclic steps,” the authors write.
“The waterfalls formed as the deeper pools trapped sediment shielding their bases against erosion, while the vertical incision continued into the next pool downstream, causing the ramp between the shielded pool and its neighboring stream to bend. steep “.
Indeed, the small model showed that a combination of flow hydraulics, sediment transport, and bedrock erosion were enough by themselves to create wavy shapes in a malleable riverbed, which when enough water falls, becomes waterfalls. It seems that nature does not like things to be flat.
Of course, a 7-meter simulation in a lab is not necessarily proof that real-world waterfalls forged their own path in the same way, but it is enough to suggest that it is possible.
Because of that, the team says that further research on this “intrinsic formation process” could help us “distinguish the formations peculiar to externally forced waterfalls and help improve the reconstruction of Earth’s history from landscapes.”
It is a way of knowing why waterfalls, rivers, lakes and all kinds of landscapes impacted by water have the appearance they do.
Reference: Self-formed bedrock waterfalls. Joel S. Scheingross, Michael P. Lamb & Brian M. Fuller. Nature volume 567, pages229–233 (2019) DOI: https://doi.org/10.1038/s41586-019-0991-z
