Mother Nature is an unquestionably prolific architect. But some of her tools are more subtle than others.
According to a study published yesterday in the journal Nature, some waterfalls might not require an outside force, like tectonic movements or glacial activity, to form. Rather, a number of breathtaking cascades could in fact come into existence through the natural turbulence of a river—a finding that could rework our understanding of Earth’s geologic history.
It’s long been thought that waterfalls can only form under the sway of an external force. For many of them, that is indeed the case: Some experience a genesis via the rapid shifting of tectonic plates, while others creep into existence when glaciers retreat, or rocks erode away at different speeds.
But the origins of other waterfalls, like the plunge pools of California’s Seven Teacups, have always been something of a mystery—prompting a team of researchers to wonder if a specific subset of these masterpieces might just be self-made.
Your garden-variety waterfall, however, might take anywhere from decades to millennia to form—a timescale not terribly conducive to the pace of research. So study author Joel Scheingross, a geologist at the University of Nevada, Reno, decided to scale things down to laboratory size. With a 24-foot-long, one-foot-wide flume made of polyurethane foam, he and his colleagues modeled a churning river of water and sediment.
Tilted to a nearly 20-percent slope, the gravel-laden liquid began to carve a channel through the foam within minutes. Slowly, as the surface grew more and more uneven, chutes and pools started to form, tugging suspended sediment down onto the foam below. As the gravel built up, a step began to take shape—and a mere three hours after the water had sprung, a small waterfall appeared. Though the lab-made spontaneous waterfall lingered for only about 20 minutes, this might translate roughly to a period of 10 to 10,000 years in the real world.
“[This] raises up a hand and says, ‘Wait a minute, everybody,’” Ben Crosby, a geomorphologist at Idaho State University who was not involved in the study, told Maya Wei-Haas at National Geographic. “We can’t necessarily attribute these landforms to some external driver or some local driver. They can pop up all on their own.”
Of course, the results of this study still await confirmation in nature. But for now, they offer tantalizing possibilities about the myriad ways in which waterfalls form—and how much there’s still left to discover about our planet’s very active geologic landscape.
“If we want to understand how the surface of the Earth changes through time, it’s important to understand all of the different processes that can change the surface of the Earth,” Nicole Gasparini, a geomorphologist at Tulane University who was not involved with the research, told Ryan F. Mandelbaum at Gizmodo. “This study gives us pause because it says that some of these might form on their own and have nothing to do with the events of the past.”