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Speleogenesis

                             THE SCIENCE  OF THE MISSOURI KARST

by RANDALL  C. ORNDORFF

 

Geological  science can benefit greatly from cave diving. Speleogenesis (the development of  cave passages) is poorly understood since much cave development occurs below the  water table in the saturated subsurface. Cave surveys, videography, and rock  samples collected by cave divers gives scientists a better chance to understand  how cave systems and large spring systems form.

The Ozarks of southeastern  Missouri contains a world-class spring system with the highest concentration of  large springs in the U.S. Protecting this natural resource is important for  water quality, tourism in National and State parks, and an appreciation on how  these large springs form.

Geologists from the U.S.  Geological Survey are working with the Ozark Cave Diving Alliance (OCDA) to  collect information from the springs to better understand the geologic controls  on how Ozark caves form. The geologists had an idea on how the rock strata  played a part in the formation of the cave, but they needed an accurate cave  survey and rock samples from various areas to prove this idea. The great  majority of the rock strata in this area are dolomite (a cousin of limestone)  that dissolves to form the caves that dominate the region. Active solution of  the rock occurs below the water table and when these caves intersect the  surface, large springs form. However, there are a few beds of sandstone that are  a part of the stratigraphic package. The idea is that ground water trapped  beneath these sandstone horizons is under pressure and enhances the dissolution  beneath the sandstone. Once the cave system gets large enough, it breaks through  the sandstone and rapidly dissolves the dolomite above as the water works its  way to the surface to form the spring.

Alley Spring, within the Ozark  National Scenic Riverways (National Park Service), is an ideal place to test the  idea. The OCDA found that the deepest part of the cave system, to date, is about  160 ft deep and levels out beneath a sandstone horizon. The cave survey verified  depth and rock samples verified sandstone rock type. Information from the cave  survey and the videography of Alley Spring show the cave system breaking  through the sandstone bed in several areas. Future work by the OCDA in Alley  Spring, and other Ozark spring systems, will help define the morphology of the  cave system and help the scientists to understand Ozark springs and  environmental affects on ground water.  

                                                                                     Randall Orndorff, USGS