Travertine is a common feature in the northern Ozarks and along the Buffalo River due to the abundance of soluble limestone there. Common in caves (stalactites, stalagmites), travertine forms by the precipitation of minerals from ground water. In the example above, it formed on the face of a bluff, giving the bluff a melted appearance.
Like limestone, travertine is composed of the mineral calcite which dissolves if exposed to acid. When rain falls, it picks up CO2 from the atmosphere and soil, and becomes slightly acidic. It then flows underground through the bedrock dissolving some limestone along the way. When the groundwater re-surfaces at a spring or seep, The pressure drops, forcing the CO2 out of the water. The loss of CO2 lowers the waters acidity; It can no longer hold the calcite in solution, and calcite precipitates as the sedimentary rock travertine.
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