Maria Reicher believes that the Nazca lines were created by ancient
Peruvians to form a kind of calendar.
She found that the lines aren't formed by marks in the earth, but by dark, purplish rocks that form borders and rows. The Nazcan people separated these rocks, which litter the desert, from the yellowish sand.
Ancient Peruvians depended on the annual spring rains for their very existence. Since they needed time to prepare their fields before
rainy season began, they made a point of learning when the seasons changed.
Reicher noticed that the lines of rocks point to a place on the horizon where the sun rose and set during the winter and summer solstice—the times when the seasons change. Her theory is that the Nazcans used these lines as a sort of grand astronomical calendar, to help them get ready for the all-important change of seasons.