Points of Interest:
- A spectacular collapsed cavern that has been designated a National Natural Landmark.
- View a large natural bridge, which spans 250 feet with a 75-feet high opening.
Grand Gulf began forming 1–2 million years ago when a long, narrow cavern formed along a zone of faulted dolomite. The ceiling was 100 feet underground and the fault extended to the surface causing the eventual collapse of the cavern. A chasm ¾ mile long, 50–200 feet wide and up to 120 feet deep developed. Sometimes nick-named the “Little Grand Canyon” this natural area features a true geologic wonder. Water that flows through the Grand Gulf system enters an underground network and is released at Mammoth Spring to the south in Arkansas.
This area is within Grand Gulf State Park. From Thayer, take Highway W six miles west to the area entrance. At the area parking lot look for the hiking trailhead that provides hiking trail access to the natural area.