The scientists observed the sandstorm they had conjured for an experiment. Or rather, had simulated.
A fast-flowing stream of water was set up to replicate the blowing of wind, sand, and dust over a desert landscape. The scientists were exploring the origins of one of the world’s most recognizable Egyptian statues, which for centuries has lain shrouded in mystery.
They had previously observed how desert formations called yardangs form due to erosion and noted a striking similarity: these formations resembled quite strongly the Great Sphinx of Giza. Yet they were entirely natural formations caused by wind.
From their observations, the researchers, from New York University’s (NYU) Applied Mathematics Laboratory, postulated that nature had a hand in sculpting the iconic polymorphic creature of Egyptian lore.
“Our findings offer a possible ‘origin story’ for how Sphinx-like formations can come about from erosion,” stated Leif Ristroph, an associate professor at NYU’s Courant Institute of Mathematical Sciences and senior author of the study.
“Our laboratory experiments showed that surprisingly Sphinx-like shapes can, in fact, come from materials being eroded by fast flows,” he said in a press release.
Observing animal likenesses elsewhere—the enormous head-like mounds in Egypt’s White Desert—they explored how the Great Sphinx might have originated as a yardang. It might have subsequently been embellished by human hands to create the now-famous statue.
To test this, they aimed to replicate desert erosion conditions—the passing of wind-blown dust and sand over solid surface material—but over a much shorter timeline. Professor Ristroph and colleagues mimicked the terrain found in northeastern Egypt, where the Sphinx lies, by using mounds of soft clay with harder material embedded within.
To simulate wind and erosion, they devised a fast-flowing stream of water to wash over the solid material.
They found that the fluid washed away much of the softer clay as a sandstorm might carve away loose rock. The harder material inside was more resistant to erosion and emerged to become the “head” of the creature.
They noted how other features formed as well—the sculpted, undercut neck of the sphinx; the paws laid out in front; the feline’s arched back—as a result of fluid dynamics.
For centuries, man has pondered the Great Sphinx of Giza, which was sculpted 4,500 years ago. How did it look in its heyday? What were its chimeric features intended to represent in the lives of the ancient Egyptians?
The researchers’ new findings may point to a more nature-driven narrative.
“Our results provide a simple origin theory for how Sphinx-like formations can come about from erosion,” Professor Ristroph stated. “There are, in fact, yardangs in existence today that look like seated or lying animals, lending support to our conclusions.”
“The work may also be useful to geologists as it reveals factors that affect rock formations—namely, that they are not homogeneous or uniform in composition,” he said. “The unexpected shapes come from how the flows are diverted around the harder or less-erodible parts.”
Professor Ristroph authored the study alongside Samuel Boury, then a postdoctoral researcher, and Scott Weady, an NYU doctoral student at the time. The study was accepted for publication in the journal Physical Review Fluids.
