La Sal del Rey
La Sal del Rey is likely the best-known natural attraction in the Lower Rio Grande Valley. It is a popular and easy to get to destination to observe wildlife and enjoyable for anyone interested in geology and history. La Sal del Rey Lake is one of three salt lakes in the area but is the only one with access to the public, it is part of the Lower Rio Grande Valley National Wildlife Refuge. The other two lakes, La Sal Vieja, and Laguna Salada, are on private land.
La Sal del Rey Lake is located just south of the southern limit of the South Texas sand sheet, in a wind carved, subcircular depression, 214 hectares in extent and 7 meters above sea level. Around the periphery of the lake is a gentle hill seven meters tall which has been mapped as a “clay dune” that formed with the deflated material carved from the lake. The lake is a closed system, it does not have an inlet or an outlet. It fills with runoff following heavy rains and the water then gradually evaporates. Depending on the time of year the lake could be completely dry allowing a crust layer of salt to form on the bottom, or it could be filled with water to a depth of 1.0 meter. The water salinity varies from four parts per thousand (PPT) when nearly filled, to 420 PPT just before the last water evaporates which is over ten times saltier than sea water! As the water level drops to a depth of only a few centimeters, salt crystals form and settle to the bottom and a crust starts to form. Most striking as the crust develops and starts aging is the cracking that occurs to accommodate the volume expansion that takes place during salt formation. Once cracked, the crust is pushed up forming pressure ridges up to 0.3 meters high that extend for tens of meters in all directions. Also common on the margins of the lake are selenite (gypsum) crystals (CaSO4) formed on the surface of the mud. The crystals are only 3 cm long and are bendable! During the late summer, the normally pure white salt develops a red hue due to the accumulation of a pink pigment produced by Halobacterium, a salt loving bacterium that reproduce in large numbers. Depending on the salinity of the water, large concentrations of Artemia salina (brine shrimp) eggs can be seen accumulating on the lake margins.
Salt has been extracted and traded from the lake since prehistoric times. The lake appears on maps from the 1700s when salt was quarried and traded into interior of New Spain. Under Spanish law, the mineral resources belonged to the crown, hence the name “The King’s Salt”. During the US Civil War, the state took over the mining and export operations. In 1866 the lake and its salt were the subject of a constitutional amendment which privatized ownership of all subsurface minerals in the state of Texas, opening the way to private development of oil, gas, and other resources. Trade continued into the 1930s. Brine was also produced here for use in oil and gas operations.
Why are these salt lakes here? The commonly assumed idea that the lakes sit on top of a salt dome has been challenged, as the area around the lakes has been drilled to 6.1 km (20,000 ft), and many kilometers of seismic lines have been run by oil companies looking for oil without signs of a salt structure. A likely explanation was offered by Barton in 1938:
…The upper ground water of the area is distinctly saline. The basin of Sal del Rey extends below the normal water level of those waters; and under the hot semiarid climate of the area, almost continuous concentration of brine takes place. The lake dries up completely during the summer and deposits a layer of salt several inches thick.
The lake can be visited year-round. The best access is through the southern entrance from Texas Route 186 with easy parking. From this entrance, there is a 1.6 km long hike to the center of the lake.
Justo al sur de los arenales del Sur de Texas, una depresión eólica alberga una laguna salada de poca profundidad pero con miles de años de antigüedad. Esta cuenca, tallada en el paisaje por el viento, es una de las tres depresiones que se formaron en la zona durante la transición del Pleistoceno al Holoceno, hace entre doce y once mil años, durante un periódico climático más seco y ventoso. Las aguas subterráneas de este punto son muy salinas, y cuando la depresión queda inundada por las escorrentías que suceden a las lluvias fuertes, se forma una laguna. Su salinidad es relativamente baja (4 partes por millar) cuando el lago está en su máxima capacidad. Al no haber posibilidad de desagüe, la depresión continúa inundada hasta que el agua se acaba evaporando, alcanzando una salinidad de 420 partes por millar, más de diez veces superior a la del agua del mar. Según se va secando la laguna, una costra de sal de hasta 20 centímetros de espesor se va formando a lo largo de este proceso estacional que hace alternar esta amplia y blanca llanura de sal seca con la aparición anual de un lago de un metro de profundidad poblado en sus márgenes con abundantes huevas rosadas de artemia salina, un microcrustáceo que vive en aguas muy salobres. El origen de la sal está en las aguas subterráneas que ascienden para reemplazar la evaporación del lago.
A estos depósitos salinos se les ha dado muchos usos diferentes a lo largo de la historia, pero hoy día La Sal del Rey es un lugar frecuentado por el público que forma parte de la Reserva Nacional de Fauna y Flora Silvestres de El Valle del Bajo Río Grande. Todo tipo de animales y pájaros se dan cita en el lugar. Se puede caminar por la costra salina e incluso observar cómo se forman los cristales de sal, que empujan hacia arriba las capas superiores cuarteándolas y levantándolas hasta treinta centímetros de altura a lo largo de varias decenas de metros en varias direcciones.
Escucha en Español – sal del rey
Just to the south of the South Texas sand sheet, in a wind-carved depression is a shallow salt lake which has existed for millennia. The wind-carved depression is one of three that originally formed during the Pleistocene/Holocene transition 12,000 to 11,000 years ago when climate was drier and windier. Ground water below it is distinctly saline, so when the depression floods with runoff following heavy rains, it forms a lake. Lake water salinity is a low - 4 parts per thousand, when the lake is nearly filled. With no outflow for the water, the depression remains flooded until the water gradually evaporates, concentrating the salts to a salinity of 420 parts per thousand, more than ten times that of sea water. As the lake dries, a salt crust up to 20 cm thick forms. This process is seasonal, and the site alternates annually between a 1-meter-deep lake with large concentrations of pink brine shrimp eggs on its margins, and a wide, dry white salt flat. The source of the salt is ground water that migrates upward to replace the evaporating lake water. The salt deposits have a long history of use.
La Sal Del Rey is popular and accessible to the public as part of the Lower Rio Grande Valley National Wildlife Refuge, where it attracts animals and birds. One can walk the white salty surface and even watch the salt crystals grow. As the crust develops, cracking occurs to allow the crust to be pushed up by growing salt crystals. Pressure ridges up to 0.3 meters high (12 inches) extend for tens of meters in multiple directions.