Tucked away in a remote area of northeastern Arizona is Coalmine Canyon, a beautiful display of weathered sandstone and shale on the Navaho Indian reservation. Stratigraphy and coal deposits can be studied, along with a large deposit of fossilized reef creatures that are approximately 100 million years old. Although the hike is difficult, most high school students in good physical shape can make the trek. It includes climbing down and up a 200 foot slope that is very steep and a 20 foot repel down a slot canyon.