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Pictured above is a travertine falls. It looks like a waterfall except that, rather than being water, it’s composed of solid rock.
Travertine is made of calcite which also forms stalactites and stalagmites. Like those familiar cave features, travertine falls form by precipitation from water; the water is flowing in a creek, over a ledge instead of dripping from a cave ceiling. As the travertine precipitates in layer upon layer, it begins to take on the appearance of flowing rock.
Dripstone features like these only form in areas where the groundwater carries a high load of dissolved carbonate minerals. This one was photographed in Searcy County, Arkansas, not far from the Buffalo National River, near the contact between the St. Peter and Plattin Formations.
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Small Spring In The Ozarks
Springs are abundant in the Ozark Plateaus Region in northern Arkansas. The spring above flows to the surface along a bedding plane between the Plattin Limestone (upper half of picture) and the St. Peter Sandstone (covered in lower half of picture). It is common to see springs at the base of limestone units. Limestone is more easily solutioned than sandstone or shale, allowing water to travel downward from the surface by cracks and through openings in the rock. Once the water reaches the sandstone (as pictured above) and can no longer travel vertically, it will flow laterally along the bedding plane between the limestone and the sandstone until it reaches an outlet such as a spring along a hillside or in a valley.