The noun 沙丘 (shāqiū) means "sand dune," referring to a mound or ridge of sand formed by wind. It is used in geographical descriptions and is also well known as the title of the science fiction work "Dune."
沙漠里的沙丘在风的作用下不断移动。
shāmò lǐ de shāqiū zài fēng de zuòyòng xià bùduàn yídòng.
The sand dunes in the desert constantly shift under the force of the wind.
我们爬上沙丘,看到了壮观的日落。
wǒmen pá shàng shāqiū, kàn dào le zhuàngguān de rìluò.
We climbed up the sand dune and saw a spectacular sunset.
这片沙丘的形状每年都在变化。
zhè piàn shāqiū de xíngzhuàng měi nián dōu zài biànhuà.
The shape of these sand dunes changes every year.