Visitors to Petrified Forest National Park may view the 21 significant geologic features that are described in this field guide (Figure 1). Many of the features and processes discussed in the Guide are not restricted to the Park; most are common throughout the American Southwest and many are found all over the world. This booklet is written for the Park visitor who is interested in geology, but does not necessarily have training in the subject. It may also be of value to the visiting geologist because the authors have described features that otherwise might be overlooked.