From Texas Rocks and Minerals, an amateur’s guide, by Roselle M. Girard
A dull, earthy calcite deposit, known as caliche, occurs in areas of Texas that have scant rainfall, such as west Texas, caliche commonly is found mixed with other materials, such as clay, sand, or gravel. This substance may be firm and compact or loose and powdery. It is thought that caliche forms when ground moisture, containing dissolved calcium bicarbonate, moves upward.
Our RV park was great for the access it provided to Big Bend, just 3 miles from the entrance. As another distinction, it easily ranks as one of our least attractive sites. It is our first just dirt site. The norm is packed gravel for RV parks, with the “lux” being asphalt or concrete. The rare rain day we had the chance to be part of last Saturday, gave a decent soaking to this weird, sloppy mud when wet, spongy soft when moist, powdery puffy when dry yet firm enough for an RV, soil. This soil, as it has been drying out, is blooming with Caliche. The picture is tracks from our truck when soil was mud, now the soil is a combination of spongy feel and powder as it dries out with the caliche forming on top.