![](http://1.bp.blogspot.com/_r0K6n0OaIZM/SSeH_-gAo3I/AAAAAAAAAJo/_HckXe4sSkU/s320/Fort+Rock+Cave.jpg)
Thousands of years ago, Fort Rock Cave was a tuff-ring island, and the cave was formed by water. Wind driven waves eroded softer material from under harder rock to create the cave. It was a similar erosion that can be seen on Fort Rock in the distance. There are over 40 tuff-rings (maars) in this basin.