Waterfalls are furious cascades of water, sometimes scoring the landscapes in which they flow as they obey gravity’s demands. From Iceland’s shimmering Skógafoss to the family of falls in New Zealand’s Milford Sound, they are zealous, aquatic showstoppers of the natural world.

Powerful though waterfalls may appear, there is a longstanding assumption that they can only form when permitted by other natural forces. Tectonic movement shifting rock around, alterations in sea level, a change from a resilient rock to a more easily erodible one are all ways in which external forces are believed to influence where waterfalls form.

But this paradigm may be about to change. By building a scaled-down river in their laboratory, a team of researchers demonstrated that waterfalls can sometimes bring themselves into existence without any outside help.

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Scientists “often use the presence of waterfalls to try and reconstruct the history of a landscape,” said Edwin Baynes, a quantitative geomorphologist at the University of Auckland in New Zealand, and who was not involved in the study. By better understanding how waterfalls can form, the new study may prompt scientists to reconsider how our planet shaped itself, and help them peer back through deep geological time with greater precision.