The coming of the Spanish conquistadors changed Peru's shape forever—literally, according to researchers who say sand ridges stopped forming along the northern coast after the Incas were forced out of the area or killed by disease after Francisco Pizarro's 1532 arrival. Phys.org explains that radiocarbon dating shows fire pits on the area's coastal ridges date back 5,000 to 400 years and were used to cook mollusks, whose discarded shells were left behind. With a dearth of vegetation to anchor the sand in place, these millions of shells, researchers Daniel Belknap and Daniel Sandweiss say, held the sand ridges in place against the wind.
And a fierce wind it was, with an archaeologist who previously studied the site telling Science that "if you are there at two in the afternoon, you get these 40-kilometer winds blowing there, and your eyeglasses are scoured." The University of Maine, Orono, researchers began mapping the ridges, some as tall as 23 feet, in 1997, and determined they also owed their genesis to earthquakes, which released sand down the Chira River and to an inlet, where shore currents took the sand northwest along the coast. There, the shells did the rest; but as the Incas vanished from the area, so too did some of the later-formed ridges. "The last 500 meters of the coast is low and hummocky, not like the discrete ridges before," Belknap says, with the two writing in the Proceedings of the National Academy of Sciences that "culture contact can lead to unexpected consequences."