Grand Gulf is a spectacular collapsed cavern featuring steep limestone/dolomite cliffs. It's now a State Park, just up the road from Thayer on Highway W. Here at Grand Gulf is a cave system with a roof that collapsed an estimated 10,000 years ago. The result is a vertical-walled canyon about three-quarters of a mile long.

The area in this photo is called Grand Junction, where two valleys, which were cave passages before their roofs collapsed, join. Rain from approximately 20 square miles drains into these valleys.

South Canyon Trail

The trail to the bottom of the canyon is 1/8 mile, descending 70 feet in 119 steps.

At the bottom of the Grand Gulf, looking up the canyon walls. The cave opening marks a point where the cave roof stopped collapsing. A little spring forms a small waterfall.

See more photos in the Master Naturalists Grand Gulf field trip journal.

The main contributor of water to the Grand Gulf chasm is Bussell Branch. This stream drains 25 square miles into the canyon, then disappears into a cave underground at Grand Gulf Sink.

It re-emerges a day or so later, 9 miles away, at Mammoth Spring, Arkansas. Mammoth Spring flows as much as nine million gallons of water per hour, part of it from the Grand Gulf.