Waterfalls are one of the most majestic things on the planet: a beautiful, thunderous display of water and physics. But where do these waterfall creations come from?
According to conventional wisdom, waterfalls are formed by external forces, such as earthquakes, landslides or sea level changes that greatly alter and interrupt landscapes and river beds. But it turns out that another force led by the interior could also be responsible.
A new study by Caltech researchers proposes a radical hypothesis on how these captivating phenomena are formed: the waterfalls are self-made.
One of the reasons why the formation of waterfalls has been a long-standing mystery, the researchers say, is because these streams evolve beyond geological times.
This made them a difficult thing to study, in a sense, reinforcing the consolidated narrative that cascades are shaped by external factors.
But just because the evolution of waterfalls is a difficult phenomenon to study, does not mean that it is impossible to understand them.
"We propose that waterfalls can form autogenously, "the authors explain in their paper," which means that cascades can be formed through internal feedback between the flow of water, sediment transport and substrate incision , in the absence of disturbances or lithological checks. "
To test their idea, the researchers built a mini-river inside their laboratory: a 7.3 meter (almost 24-foot) canal made from a foam" synthetic rock " polyurethane, and
They placed small gravel pebbles in the canal to replace natural rock sediments, and then they ran a steady stream of water through their virtual waterfall, essentially letting nature take its course.
 Within a few hours, the constant flow of water and rock began to erode the soft bed of the river of foam, and not evenly.
"Along the riverbed, the variations in the erosion of decimeters caused repeated convex crests and concave depressions, which grew in width to form cyclic steps ", writes the team.
" The waterfalls formed by deeper pools hid sediments that shielded their bases against the erosion and, while the vertical incision continued into the next downstream pool, causing the slide between
In fact, the mini-mockup showed that a combination of flow hydraulics, sediment transport and substrate erosion is sufficient to alone to create undulating shapes in a malleable riverbed, which with enough water to fall, become become waterfalls.
"Nature does not like things to be flat," said one from the Caltech team, Joel Scheingross (now with the University of Nevada, Reno) New Scien tist .
"Some areas are being eroded a little more and are somewhat deeper, while others remain somewhat less profound."
Of course, a 7-meter simulation in a lab isn't necessarily proof that the real-life waterfalls of the world have forged their way the same way – but it's enough to suggest it's possible.
For this reason, the team says that further research on this "intrinsic formation process" could help us "distinguish externally constructed waterfalls [and] to improve the reconstruction of Earth's history from landscapes".
Taken to the maximum extent, the results indicate that it may be necessary to re-examine a whole series of scientific hypotheses on how and why waterfalls, rivers, lakes and all other types of landscapes affected by water appear as they do.  Essentially, the falls have become even more majestic.
"If we want to understand how the surface of the Earth changes over time, it is important to understand all the different processes that can change the surface of the Earth", geomorphologist Nicole Gasparini of Tulane University, who was not involved in the research, told Gizmodo.
"This study makes us reflect because it says that some of these could form themselves and have nothing to do with the events of the past."
The results are reported in Nature .