Monthly Archives: July 2015

Another view of travertine falls

Travertine Fall over St. Peter ss, Searcy County 2To see the original post on travertine falls click here

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Geopic of the week: Travertine falls

Travertine Fall over St. Peter ss, Searcy County

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.

For another view of this travertine falls click here

Geopic of the week: Breccia

Dolostone breccia (1) corrected

A Breccia is a rock made up of angular rock fragments mixed with finer sediment.  The one above was deposited about 450 million years ago (Ordovician) in a shallow sea in what is now the Ozark highlands, north of Mountain View, Arkansas.

Breccias can form by a variety of processes such as landslides, volcanic eruptions, storm events, cave and sinkhole collapses and others.  This one likely formed during a storm.  Turbulent ocean waves and currents washed fragments of marine organisms (dark gray) into calmer water where marine mud (light gray) had recently accumulated.  The turbulence ripped some of the mud up and mixed it with the organic material.

Breccias are just one of many clues, recorded in rocks, that help geologists understand how the earth has changed through time: a story that itself constantly evolves as new rock is unearthed and studied.

For more views of breccias click here