Valles de San Pedro

After a much needed siesta, we hit the road to visit Valle del Muertes and Valle del Luna.

These areas are known for beautifully incised and sculpted sandstone and siltstone. The geologic formations are primarily lakebed sediments, interbedded with gypsum and other evaporite deposits. Periodic catastrophic landslide, debris flow and volcanic rocks are sandwiched within the lakebed sediments. One can image the depositional environment for these rocks: a salar much like those we have been visiting received sediment eroding off nearby mountains. The lake basin was probably closed and high evaporation rates resulted in high salinity in the lake. During particularly dry periods, the salts precipitated out of the lake water, depositing gypsum salt and other evaporites. Periodic catastrophic volcanic activity resulted in the landslide, debris flow and volcanic deposits.

Long after the lake bed sediments were deposited, they were folded due to subterranean movement of massive salt deposits.

Here lake bed sandstone is cut by fractures which have been subsequently filled by migration of gypsum. a single gypsum bed draws the "u" from left to right.

Kate stands on an island of lake bed sediment. Note the geologic layers (beds) running toward the horizon. These sediments have been turned from horizontal to near vertical.

Both Valles are flanked by stand dunes. These dunes are composed largely of volcanic detritus that was blown up against the flank of Salar de Aticama. The Great Sand Dunes in Colorado are similar in that they are composed of volcanic sand from the San Juan mountains that was blown across the San Luis Valley and trapped at the base of the Sangre de Christo mountains.

Having visited the Great Sand Dunes numerous times, Kate and Dan knew exactly what to do after reaching the top of the dune: find the steepest part with the loosest sand and run down!

After tromping around Valle del Muertes, we visited Valle del Lunes, which is similar to Valle del Muertes, but is more travelled and offers less freedom to beat your own path.

Dan sketches.

Sunset.

After a great final full day in the Aticama, we dined at a Todo Natural restaurant in San Pedro. It’s located on the main steet and was absolutely delicious!