The "cliffs of chalk" refer to steep, white rock formations primarily made of chalk, a soft, white limestone composed mainly of calcium carbonate. These cliffs are often found along coastlines, such as the famous White Cliffs of Dover in England, which rise dramatically above the sea. The chalk is formed from the remains of tiny marine organisms that accumulated on the ocean floor millions of years ago. Chalk cliffs are not only visually striking but also serve as important geological and ecological sites. They provide habitats for various plant and animal species, including seabirds that nest on the ledges. The erosion of these cliffs by wind and waves continually shapes their appearance, making them dynamic natural landmarks.