Hot Springs National Park is found within the Zig-Zag Mountains, a section of the Ouachita Mountains of central Arkansas and eastern Oklahoma. The name "Zig Zag" comes from the sharply angular folds of the rock when seen from above. The Ouachita mountains were formed during the collision of two tectonic plates around 300 Ma (million years ago). The Appalachian Mountains were formed at about the same time, and were a result of very similar forces. Geologists call the formation of these two mountain systems the Tectonic Orogeny, or mountain-building event.
The area of the park is characterized by steep, mountainous terrain. Although once more jagged, time has reduced the steep peaks of ancient mountains into more gently rolling hills. Visitors will notice that rock layers exposed along bluffs or road-cuts appear to be tilted, or even to stand up straight, rather than lay flat. This tilting of rock layers is a result of extreme forces that "pushed" the rocks into the tilted position, which we can observe today.