Sinkhole Basin
Designated as a natural area since
National Park Service,
The Nature Conservancy,
L-A-D Foundation
Missouri Department of Conservation – Ozark Regional Office
Contact Phone

Points of Interest:

  • Explore a large and remote natural area with over 14 different natural community types.
  • See shortleaf pine woodlands in the process of restoration.
  • The longest sinkhole valley in Missouri.

Natural Features Description:

Over 6,000 acres of hills and hollows draining into Boyds Creek and the Current River. At the center of this natural area is a complex of sinkholes, depressions caused by the dissolving of the underlying rock, in this case dolomite, followed by a collapse of the land’s surface. What is known as the “sunkland” is the longest conspicuous sinkhole in Missouri, nearly a mile long, 200 feet deep and 600 feet wide. It is so large that to the casual observer it looks like a normal valley. Four separate bowl-like depressions form the basin of the “sunkland” sinkhole valley. One of these sinks, known locally as Big Yuccapin Basin, contains a pond marsh community. In wet winters and springs this basin will have standing water upon which a “floating mat” of live herbaceous plants and decaying plant matter forms. Three way sedge, other sedges in the genus Carex, marsh St. John’s wort, water plantain and other wetland plants form the vegetation mat. The smaller Little Yuccapin Basin contains a shrub swamp of buttonbush. Ringed salamanders, an ambystomid salamander endemic to the Ozark ecoregion, utilize these wetlands. The wood frog, considered a glacial relict species, has been documented from the pond marsh. To the south of the “sunklands” is Burr Oak basin, a complex of three sinkholes that are larger, more round and less deep. The area known as “bog basin” is a large open pond marsh dominated by three way sedge, hop sedge, and perfoliate boneset. In the summer, the pink blooms of meadowbeauty occur across the marsh. Virginia sneezeweed, a plant species listed as threatened by the U.S. Fish & Wildlife Service, also occurs on the margins of some of the pond marshes. This species occurs in sinkhole pond habitats in the Ozarks and in the Shenandoah Valley of Virginia – a disjunct range of 500 miles.

Along the twisting and turning valley of Boyds Creek are wooded ridges of oak, hickory and pine punctuated by many small dolomite glade openings. The upper reaches of Boyds Creek are typically dry except after rains. Broader ridges occur in the headwaters of Boyds Creek on the south side of the natural area. These areas support cherty woodlands dominated by shortleaf pine, black, post, scarlet and white oak, and black and mockernut hickory. Here thinning and prescribed fire are being utilized by resource managers to restore a pine-oak woodland – a community type once extensive in the Lower Ozarks. The Ozark pinery was decimated by unsustainable logging practices in the late 19th century followed by widespread intensive fires and open-range livestock grazing for decades thereafter. Today a variety of conservation partners including the Mark Twain National Forest, the Missouri Department of Conservation, the Ozark National Scenic Riverways, The Nature Conservancy and Pioneer Forest are working on restoring part of the once widespread shortleaf pine – oak woodlands that historically supported the new extirpated red-cockaded woodpecker and brown-headed nuthatch.

On the east side of the natural area is Pulltite Spring and the area known as “triple sink.” Pulltite Spring averages a daily flow of 20-30 million gallons. Water enters an underground labyrinth of passageways and channels through the karst landscape of the surrounding region to be discharged here. The name “pulltite” comes from the history of a grain mill that was established here in the late 19th century. To access the mill (powered by the spring), the leader of a horse or mule team had to pull tight on the reigns to guide the team and wagon down the hill. On the way up the livestock would have to pull the load tightly to make it up. Hence the name “pulltite” for this spring. Up the hill from the spring is a set of three deeply set sinkholes, or “triple sink.” From the ridge top above to the lowest sinkhole is a distance of nearly 100 feet. Along the steep east facing bluffs above the Current River occurs a population of blue monkshood, a rare plant species more common to the southern Appalachian mountain forests.

Access Info

The natural area lies within the large Sunklands Conservation Area. From Summersville head northwest for a short bit on Highway 17 then turn right (north) on to Highway K. Travel north on K for 5 miles, continuing on Highway K at the “Y” intersection. About 4.5 miles north of the Highway K and KK intersection on Highway K, turn right (east) on Shannon County Road (gravel) K-B. Head east on K-B for almost a half-mile and turn right (due south). After a third of a mile, stay to your left, continuing on K-B. In another mile you’ll come to an intersection. Turn right (south) here. In another mile you will come to a “T” intersection. This is the western-most point of the natural area. Sunklands Conservation Area gravel roads 370 and 360 provide access to the perimeter of the area. No marked trails occur in the interior of the area but a system of old logging roads occurs on the ridges. Consult a map for further information. To access the east side of the natural area, go to the Pulltite canoe access and campground maintained by the Ozark National Scenic Riverways (573-323-4236) which is west of Highway 19 off Highway EE. The natural area is directly across the river from the canoe access. Hunting and fishing are permitted. A map and compass are recommended for exploring this area.