Welcome to the Petrified Forest National Park! The word “forest” may mislead visitors. The park is in a desert. And the word “petrified” -- which can mean “afraid”-- may scare visitors away! But fear not. “Petrified Forest” gets its name from the trees that have, over millions of years, turned to stone. That natural process is called fossilization. Much of the Petrified Forest formed from tall trees called conifers. They grew over 200 million years ago near waterways. During floods, water forced the trees to be pulled up from the ground. Over time, the wood from the trees became petrified. The Petrified Forest National Park is one of the wonders of Arizona. It sits within the Painted Desert. A Spanish explorer in the 1500s gave the place its name. It is easy to see why. The desert looks like an artist’s canvas. Brilliantly colored mudstones and clays cover the land as far as the eye can see. They contain bentonite, a clay that is the product of changed volcanic ash. The oldest geological formations in the park are about 227 million years old. Differently colored formations show different time periods. The Blue Mesa formations, for example, have thick bands of grey, purple, blue and green mudstones. They are about 220 million years old.