THIS LAND 



Going with 

 the Flow 



All iiudcvgYoiiiid stream liiiks two scenic spots. 



By Robert H. Mohlenbrock 



As natural attractions "worth a 

 detour" (as the guidebooks 

 have it), Grand Gult and 

 Mammoth Spring Hve up to their 

 names. They also share a physical 

 connection, though they lie miles 

 apart in two different states. But more 

 on that connection later: my travels 

 took me first to Grand Gulf State 

 Park, in southern Missouri. Standing 

 on the edge of a rocky limestone 

 blutf, I surveyed a canyon 135 feet 

 deep, nearly a mile long, but nowhere 

 more than 200 feet wide. This was 

 Grand Gulf, whose narrow propor- 

 tions have earned it the nickname 

 "Missouri's Little Grand Canyon." 



Grand Gulf is a feature of the 

 Ozark Plateau, a 50,000-square-mile 

 region of low^ mountains, caves, dry 

 upland forests, clear rocky streams, 

 and sinkhole ponds that extends 

 across central and southern Missouri, 

 northern Arkansas, and neighboring 

 parts of Kansas and Oklahoma. In 



Water from Bussell Branch contributes to 

 the output of Arkansas's Mammoth Spring, 

 whose waters cascade over a dam built 

 in 1888 from hand-quarried limestone. 



the region surrounding 

 the canyon most of the 

 rocks are dolomite and 

 other forms of lime- 

 stone, formed 450 mil- 

 lion years ago by de- 

 posits at the bottom of 

 a shallow sea. Over the 

 ages, streams carved the 

 surfaces of those porous 

 rocks and trickled 

 through cracks, slowly 

 creating underground 

 passages. At the same 

 time, the limestones 

 underground were 

 gradually being dis- 

 solved away, causing the water table 

 to fall and turning the upper passages 

 into air-fiDed caves. In places, the 

 cave roofs collapsed, leaving sink- 

 holes on the surface. Such depres- 

 sions, which are usually small, are 

 scattered across the Missouri Ozarks. 

 The ones that lack good drainage fill 

 up to form sinkhole ponds. 



Grand Gulf is kin to these depres- 

 sions, but Its size puts it in a class by 

 itself. It was created when the roof of 

 a huge cave collapsed, apparently in 

 sections, sometime during the past 

 10,000 years. Chunks of the cave 

 roof are strewn across the bottom of 

 the chasm; one section of rock that 

 did not collapse forms a natural 

 bridge that spans a gap of 200 feet. 



The drastic change in topography 

 engendered by the collapse diverted a 

 nearby stream into the canyon, 

 where it was "pirated," or captured. 



Bussell Branch streambed, at times dry, leads to a cave 

 in Grand Gulf, Missouri. Stream waters that vanish 

 underground here re-emerge at Mammoth Spring, 

 more than seven miles away. 



by existing underground passages. 

 Called Bussell Branch, the stream 

 flows through Grand Gulf until it 

 disappears into the mouth of a cave 

 at the lower end of the canyon. 



Although bare patches of lime- 

 stone lie all around the rim, enough 

 soil accumulates in small surface 

 depressions to support low-growing 

 plants; trees and shrubs gain a firm 

 foothold by sending their roots into 

 cracks in the rock. The rim is weU 

 exposed to sunlight, so the flora 

 must tolerate dry conditions. Some 

 of the trees and shrubs have thick, 

 leatheiy leaves covered by a wax")' 

 cuticle that prevents excessive loss of 

 water on the hottest days. To my 

 surprise, at one place, clinging 

 tenacit:)usly to the edge of the clitf. I 

 saw a shrub known as ninebark. a 

 member of the rose family. Usually it 

 grow s along Ozark streams, and in 



I 



48 



NATURAL HISTORY February 2006 



