Dunes

Dunes

Shifting sands and aeolian processes.

The Mojave Desert is home to one of the most exotic environments in the United States: dune fields. The two closest to the Mojave National Preserve are the Kelso Dunes and the Dumont Dunes. On the surface level, dunes may seem very simple, and they may be if you were to consider only a few aspects, but the dunes in the Mojave have many interesting features that can tell us how they formed in the first place, from the wind patterns on the dunes and the mineralogy of the sediments they’re composed of, and how certain ecosystems adapted to them.

Sand Supply

Very fine grained, wind blown sand makes up the sediment sand dunes. For a sand dune there needs to be a constant flux of sediment for the dune to remain persistent. These sources come from locations like barren rock, distal alluvial fans, dry lake beds, ephemeral washes, and rivers where sand and fine sediment are washed away and sorted by water and wind. Weathering during rainfall and water runoff causes rocks to break down through the process of chemical weathering and when on sloped surfaces, is eroded downstream. This broken-down material is naturally sorted by size and density whereas lighter sediments are carried further because they require less energy to move. After the water source dries up, the wind further sorts the sediment and dust; finer grains tend to be concentrated at sand dunes because the wind doesn’t have enough energy to move the larger grains of sediment.

Dune Morphology and Characteristics

Many different sizes and shapes of dunes such as star, linear, parabolic, crescent (most common), and the rarest is a dome. Kelso dunes are thought to have formed between 2400-9000 years ago, throughout the seasons dunes shift between 30-40 feet as winds shift.

Kelso Dunes

Very Fine grained, groups of eastern and western groups of dunes. Eastern dunes sand sourced from Providence mountains. Western group of dunes primarily sourced from Mojave River alluvium. While viewing Kelso from a distance we were able to see darker portions of the dunes which we determined to be heavier metals, mostly iron which must have come from the Providence mountains.

Home to rare and endemic species such as the Kelso Dunes Shieldback Katydid, but also rare lizards, tortoises, and more.

Dumont Dunes

When it comes to Dunes in the Mojave, Dumont is often the second pick when compared to Kelso Dunes; the Kelso dunes are nearly several times larger than the Dumont Dunes which stand at a size of around 13 square kilometers. Dumont Dunes is supplied with sediment from the surrounding landscape, the sand doesn’t travel too far; in the north, there are the Dumont hills, in the northwest, the Amargosa River, and in the southwest, there is the Salt Spring Hills: all of these sources provide sediment to the Dunes. Another hill, the Valjean Hills, may also provide sediment but it isn’t known for certain. 

The Dune’s height changes seasonally; in the winter and summer months they stand the tallest at around 120 to 80 meters; in the transitional months of spring and fall, they are about 40 to 10 meters tall. Further on this note, the dune type also changes with the season; when northern winds come down in the winter they will create southern-facing star dunes, and when the southern winds come up in the summer they will create northern-facing barchanoid dunes. The dunes stretch around 31 miles long.

There may only be one species that lives in the Dumont Dunes, the Mojave Fringe-toed Lizard. The lizard's fringe toes have adapted to the desert dunes so it could more easily move around in loose sand. The Fringe-toed Lizard’s conservation status is categorized as “Least Concerned”, meaning they are doing just fine. Much of the Dumont Dunes is included in an “Off-Road Vehicle Area” for many recreational activities like offroading, camping, hiking, etc.; although, if the Fringe-toed Lizards become an endangered species this area would be bound to change.

Before seeing them in person, it was easy to surmise the dunes as insignificant when compared to the monumental Kelso Dunes. When we first visited the Dumont Dunes it was as if the dunes knew of our misinterpreted and underrated notion and hated us because of it. The dunes had aggregated all of their hate and anger together and cast it upon us in the form of tiny granules of sand that painfully made their way into our clothes, hair, mouths, and our eyes. This was the price to pay for ignorance, the price paid for having defied them. Because of the suffocating particulates and our exhausted sunlight, we had to retreat without knowing if we would return. As science goes, it is often the thirst for answers, and the disrespectful dry desert sand had made us very thirsty. We returned again to the dunes coarsened and determined for a purpose that felt more like destiny rather than curiosity. On our second visit, the dunes had carried only a gentle breeze that whispered to us of their dormant power, taunting us with every wisp. Defiantly, we climbed to the top of the largest dune we could find; even though the slopes were steep and the sand gave way beneath our feet, we did not falter. Upon the crest we found that the Dumont Dunes contained… dunes, massive dunes that were ~40 meters high composed of uniform grains, and at the time the dunes had still displayed a star dune pattern. Surprisingly, the malignant dunes had a playground. There was also a small amount of trash at the dunes but very little of it looked as if it was littered recently.

Ecology and Habitat

Very few species live in sand dunes because of the constant movement of sediment and unstable environment.  There is little to no soil for plants to take root. Only some grasses and shrubs are able to do this. Most animals are not able to survive off the limited resources and lack of shelter. The Dune Evening Primrose blooms through evening to midmorning from March to May. The Fringe-Toed Lizard is not endemic to the Mojave, but they thrive in dune ecosystems. They feed off of small insects and beetles, spiders, seeds, and stems of plants. They hide from their enemies by burrowing in the sand or escaping quickly as their fringe toes act as snowshoes allowing them to run across the sand with ease. They also bury their eggs in the sand, but reproduction varies depending on the amount of moisture. The Kangaroo Rat’s main predator is the Kit Fox. Both of these animals are nocturnal and are usually only spotted during dusk. The sidewinder rattlesnake is endemic to southern California, venomous, and likes to burrow in the sand for cover. They do not move around like typical snakes with their underbelly scales and throw their head forward and pull the rest of their body with them.

Unfortunately, we did not see any wildlife and very few plants at Dumont Dunes, this is most likely because of our proximity to the recreational vehicle area.