14 DAY TRIAL // Recent investigations conducted on a patch of desert in southern California revealed the existence of four types of sand dunes in the large erg called the Algodones Dunes. The fact that such a heterogeneous amalgamation of features exist in a relatively small space puzzles geologists.
The presence of the erg itself is interesting, considering that the environmental factors that caused its development are the same that gave birth to the irrigated green fields of the Imperial Valley. The latter are located only a few miles away.
The Algodones Dunes erg is located near the border with Arizona and the Mexican state of Baja California, and is a large sand dune field created, of all things, by waves in a temporary lake.
That landscape feature forms when silt covers up the entire Colorado River Delta, forcing the waters to move into Imperial Valley. This leads to the creation of a large body of water, but which slowly disappears as the Delta recovers.
However, waves slamming into the lake's eastern shore deposit very fine sediments in the area. Over time, those sediments gave birth to the sand dunes. Interestingly, though the source was the same, the outcomes are rather different, experts now say.
The erg is 72 kilometers (45 miles) long by 10 kilometers (6 miles) wide, and features dunes whose alignments is correlated to the directions of northerly and westerly winds, Our Amazing Planet reports.
First and foremost, the Algodones Dunes contain large, compound crescentic dunes. These impressive accumulations of sand can primarily be found in the middle of the field. Interestingly, this type of dunes is characterized by developing secondary dunes on top of the primary ones.
Measurements conducted at their base indicate a slow, but constant, south-bound motion of these features. They are estimated to be between 15,000 and 18,000 years old.
Another predominant type of dunes is the simple crescentic one – of the variety most widely found in any of the world's desert. These structures get their shapes from the immutable unidirectional actions of prevailing winds.
Linear dunes and associated zibars complete this image, experts say. These are newest-formed dunes in the erg. According to the new research, the zibars criss-cross the linear dunes because the latter are moving eastwards from their original position.