![]() Other chemical reactions paint the soil’s colors. Chemical reactions convert some minerals contained in the parent materials into clay minerals. Physical and chemical weathering reduces the sizes of coarse particles. Water is responsible for most of this work of alteration and transportation of materials in soils, even in deserts. ![]() Over time, the composition and location of substances within the developing soil change and move around, altering the soil’s characteristics. Soils initially form within the physical matrix of the parent material. Of wind-blown sand in the dune fields of the Gran Desierto in northwestern Sonora and the Cactus Plain east of Parker, Arizona, provide yet another kind of soil parent material. The mountains themselves possess various rock types, slopes, and exposures that offer a complex array of different soil-forming environments. The sediments transported all the way to the floors of these basins are usually much finer-sands, silts and clays. That spill out of mountain drainages into adjacent basins cover much of the face of the Sonoran Desert (see the chapter “The Geologic Origin of the Sonoran Desert”). The varied geological terrains of the Sonoran Desert provide many different kinds of parent materials in which soils form. Characteristics of these soils also greatly affect, and are greatly affected by, desert organisms. Of these diverse features of desert soils have taken thousands of years or more to form. In the more arid parts of the Sonoran Desert,Ī layer of small stones that can be as tightly interlocked as pieces of an ancient Roman mosaic, and are coated with dark, shiny rock varnish. Desert soils may be gray-colored, brown, or even brick red. I’ve learned so much since then the soils found throughout the Sonoran Desert are far more varied and complex than any I studied as a college student in the Midwest.ĭesert soils are downright unusual! They vary tremendously in texture many are sandy and gravelly, while When I first came to the Sonoran Desert nearly twenty years ago, I hardly considered that anything deserving the label “soil” existed beneath the desert’s gravelly and rocky surface. I grew up in Nebraska and had a narrow view of “soil” for the first part of my life soil was the deep, dark loamy stuff that supported the bountiful agriculture of the Corn Belt.
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