A sine wave

A picture trending on social media shows a sand mountain range with a sin wave structure. From multivariable calculus point of view, the height function is not Morse. The maxima are on a curve. As usual on social media, it is at first difficult to figure out who is the author of the picture According to this tweet the photographer should be Nik Barte and called "Biorhytms and appeared in Desillusion magazine