County of park: Oregon County
Location of park: MO W, 12 miles west of Thayer
DNR Phone: 1-800-334-6946
Grand Gulf Phone: (417) 264-7600
Markers: Missouri state parks and historic sites preserve and interpret the state's outstanding natural and cultural features while providing recreational opportunities. Grand Gulf State Park preserves one of the states's most significant geologic wonders - a major collapsed cave system, often called the "Little Grand Canyon." When a portion of the cave roof collapsed, it created a three-fourths-mile-long canyon and one of the largest natural bridges in Missouri.
To understand its origin, one must understand the geology of the area. The limestone and dolomite bedrock here are very soluble in the mildly acidic groundwater that percolates down from the surface. The water seeps into the fissures and fractures in the bedrock, eventually enlarging the cracks into caves.
here at Grand Gulf is a cave system with a roof collapse and estimated 10,000 years ago. The result is a vertical-walled canyon about three-quarters of a mile long. Bussell Branch, a surface creek that drains about 25 square miles, empties into the chasm through a process called stream piracy. All of this water passes down the length of the chasm, under a 250-foot natural bridge (an uncollapsed remnant of the original cave) and back into the open canyon, at the lower end of the chasm, it enters the mouth of the remaining underground cave system. It travels nine miles underground, and re-emerges at Mammoth Springs in Arkansas. Mammoth Springs flows as much as nine million gallons of water per hour, part of it from the Grand Gulf.
The mouth of the portion of the cave that has not collapsed (at the downstream end of the chasm) is blocked only a short distance inside by mud and debris that allows the water from Bussell Branch to percolate through, but bars human access. In the early 1990's a robot vehicle, equipped with a digging tool and remote camera, penetrated a significant distance into the cave. As a result of this reconnaissance, it was determined that is no feasible way through the massive blockage to gain access to the rest of the cave.
Early explorers were able to enter the cave. Luella Agnes Owen, in her book Cave Regions of the Ozarks and Black Hills (1898), recounted her explorations in the Grand Gulf. After entering the cave at the downstream end of the chasm, "The ceiling dipped so we were not able to stand straight, and the guide said he had never gone farther; but to his surprise here was a light boat which I am ready to admit he displayed n eagerness to appropriate to his own use, and swimming about it, close to shore, were numerous, small, eyeless fish, pure white and perfectly fearless; the first I have ever seen, and little beauties," she wrote. Owen used the boat to explore the underground system for a considerable distance.
Access to the deeper portions of the cave remained possible until the 1920s when a severe storm washed many downed trees and other debris into the gulf, filling the cave. Today, heavy rains fill the gulf to depths exceeding 100 feet, and the water drains out slowly over a period of several weeks.