The part of the Ozark Uplands that occurs in the southern part of Missouri is underlain by limestone and dolomite. These rocks are relatively soft and subject to swift erosion from the effects of the slightly acidic water that percolates through it. Because of this tendency to erode swiftly from the acidic action of the groundwater, the Ozark plateau in this part of the state is honeycombed with vast cave systems.
One of these cave systems collapsed about 10,000 years ago. Roughly a one-mile stretch of cavern had its roof give way, revealing a deep scar more than 130 feet deep. With a width that is less than the depth in many places, this canyon is actually a true chasm, and arguably the most spectacular physical feature in that part of Missouri.
The Grand Gulf is protected as a small state park and natural area. There
are a number of trails that navigate the rim of the canyon, and one that descends to the floor of one branch of the chasm. However, there are no official trails into the base of the canyon itself. There are, though, several unofficial trails that one can take to the bottom to get the best views of the Grand Gulf.
One of the features of the Gulf is a section of the former cave roof that did not collapse with the rest of the cave 10K years ago. This section is now the largest natural stone arch in the state. One side of the arch is over 75 feet high, while the opposite end is about ten feet high. It's quite an experience to walk beneath it and look up at the limestone roof.
The floor of The Grand Gulf is quite lush with plant life and rather damp. There was once a cave outlet at the low end that could be navigated, but a flood in the 1920s permanently plugged the cave entrance. Because of this plug, the chasm sometimes fills with water to a depth of 100 feet and which drains slowly over the course of weeks to reveal the chasm once again. Eventually, the water that drains through this system emerges some few miles south in Arkansas as that state's largest fresh water spring,Mammoth Spring.
From West Plains
Grand Gulf State Park is 25 miles from West Plains. Travel south on U.S. Hwy. 63 to Thayer. Turn right onto Hwy. 19 and then right onto Route W, which leads into the state park.
Grand Gulf State Park is 12 miles from Arkansas. Travel north on U.S. Hwy. 63 almost to Thayer. Turn left onto Hwy. 19 and then left onto Route W, which leads into the state park.
Grand Gulf State Park is 135 miles from Springfield. Travel south on U.S. Hwy. 60 to Cabool. Take U.S. Hwy. 63 south to Thayer. Turn right onto Hwy. 19 and then right onto Route W, which leads into the state park.
Grand Gulf State Park is 118 miles from Sikeston. Travel west on U.S. Hwy. 60 to Poplar Bluff. Take U.S. Hwy. 67/160 west to U.S. Hwy. 160. Continue to Doniphan then travel west on Hwy. 142 to Thayer. Turn north on U.S. Hwy. 63 and continue to the caution light at Hwy. 19. Turn left onto Hwy. 19 and then left onto Route W, which leads into the state park.