Rocks are famous for staying put. If something is as “solid as a rock,” you assume that it’s not going to change or go anywhere.
However, in reality, rocks are always changing and on the move. Nature’s constant recycling of them can be seen in mountains, rivers, oceans, volcanoes, canyons, and earthquakes.
Rocks come in about 100 varieties. There are also approximately 3,500 minerals—the stuff of which rocks are made. Together, rocks and minerals pave streets, give color to paints, decorate jewelry, and put “lead” in pencils. Rocks are added to food—iron into cereal and chalk into bread—to make bones strong. We put rock salt on food for taste, and we also use salt to preserve foods. Rocks are found in toothpastes and cosmetics. While rocks may not have supernatural powers—as many once believed—they do have an influence on our lives.
