Location: Kansas River Valley original floodplain, about midway between Topeka and Kansas City
Method: Crude sampling from leaves on ground, dust settled within house, etc., examined under 20X stereo/binocular microscope
The soil here is composed of many types of particles, deposited by both water and air currents over many thousands of years.
Water-borne deposits, which form the greater proportion of the total quantity of deposited material, are very much less now, due to flood control practices instituted since the mid-19th century (but mostly since the disastrous 1951 Flood) that prevent harmful area flooding, and thus also prevent the beneficial settling out of the material carried by the flood water.
Before the latter half of the 19th century the land in this valley was replenished and built up higher, incrementally over a vast span of time, by the many flooding/settling cycles which had been occurring since the original formation of the valley.
The soil, almost completely alluvial- sedimentary and layered- was built up by flood deposition to a depth, or thickness, of some dozens of feet.
It is a loose, sandy/loamy mix, which generally feels more smooth than gritty, although not as smooth as, for example, high-clay, low-sand soils, which are very slippery.
Conversely, although there is considerable sand, comprised mostly of crystalline quartz, the local soil does not has the gritty feel of what is usually called "sandy" soil.
I should note that the adjective "sandy" is vague and subject to individual interpretation. However, measurements of particle size and type, or tables listing their relative proportions, are not necessary for such a general description.
The price of settlement and of agriculture has been, in part, the starvation of the land by preventing its receiving countless tons of new organic and inorganic material previously washed from the higher land at the edges of the valley floodplain. In this way, the potential of the land is diminished.
However, soil which was water-deposited at one time has almost always been moved twice, three times, four times, ten times, fifty times, or more, by the action of rainwater and its runoff over the years, thus depleting, not enriching, some portion the area affected.
Under natural processes, this soil ends up in the river and is then taken some distance, variable depending upon factors such as particle size, density, and the river's current velocity, downstream.
Some of it- the finest of the particles, of "nano" scale- will be taken all the way down the river system, from the Kansas River to the Missouri and into the Mississippi, and finally end up in the Gulf of Mexico, or even the ocean.
Human settlement and agriculture since the 1850's have done much to combat water erosion. Dikes,or levees, and their companion ditches, were built on the flat areas. Moreover, cultivation of the valley-edge slopes has been minimal, the upland areas being a mix of natural woodland, active pasture for cattle, and fields of grass for hay.
This kind of beneficial work- levees and ditches- has been done, with or without governmental assistance, throughout the river basin wherever the land has been farmed for crops.
There is little or no grazing to speak of in the bottom land (the flat expanses adjacent to the river) of the Kansas River alluvial plain, which is maybe an average of six to ten miles in width.
To the eye, much of the bottom land appears dead-level, except for the interruptions of stream courses; the area around these is locally depressed and sloped towards the creek or stream to a slight extent.
In the developed fields, the natural streams have often been redirected to some course off to the side, making the field more tractor-friendly.
Of valley land in production, almost all is used for three feed crops: corn ("cowcorn"), milo (sorghum), and soybeans.
The crops require various forms of cultivation, and cultivation, and road travel of cultivating vehicles, raises much dust. Most of it settles to ground in minutes, within a few hundred feet of its starting point, but a certain amount of the stirred-up soil is in the form of particles so fine that they are able to remain airborne for long periods, and are therefore able to travel miles, perhaps many miles, before finally dropping out of the sky to touch the ground again.
In a few words, the end result, or one end result, is that there is a constant and imperceptible "snowfall" of soil particles that are fine enough to become, in terms of their relationship to even slowly moving air, almost weightless.
There is nothing new in any of this. But it is not generally known that the local dust is composed largely of quartz sand, one of the most common forms of silica (silicon dioxide, SiO2).
If a fallen leaf is picked up from the ground, or if a blade of grass is carefully cut and placed under twenty diameters of magnification, it can be seen that the leaf or the blade of grass is "sugared", sometimes almost completely but more often as many discrete particles with spaces between, with material that contains a high proportion of crystalline quartz.
They look like sand grains, under 20X magnification, as if one grain of normal beach sand were crushed to fifty or one hundred pieces, crushed to the point that, although still sharp and hard-edged, it begins to feel smooth, more like clay and less like sand, to the rubbing fingers test. But it is quartz sand, and sharp-edged, and so must be abrasive.
To some extent it permeates everything inside and outside of homes in this area, and may contribute to wear in motors or any device using bearings.
It gets into clothing and contributes to wear by microscopic cutting or nicking of clothing fibers.
Since the fine sand is in the ambient air, it is breathed in, but not out, to some extent, although this effect has not been considered much of a health hazard. However, though the effect must be relatively small, the very fine sand falling out of the sky, steadily and imperceptibly, would seem to eventually create conditions identical to early stages of silicosis or to other types of disease caused by dust.
The point is not to say that this fall of very fine quartz sand from the sky means the sky is falling, although in a literal sense it means almost exactly that.
The sand falling from the sky is not a severe and imminent threat to public health.
It may or may not be a risk factor for older people and people with certain conditions such as asthma or COPD or emphysema. It may, or may not, affect the health of children who grow up breathing it day after day for years on end, as many do.
The point is, shouldn't people know it exists? Most people around here, of all those I have asked anyway, didn't know it, had never considered it.
The fine rain of sand is imperceptible, in that although it is commonly noticed that there is dust, airborne dust which can settle anywhere, the dust is rarely if ever thought of as sand, but rather, it seems, it is popularly considered to be "soft" and harmless: "Oh, it's just normal", is likely the most common opinion among those who think of it at all.
But a large proportion of the invisible sky-fall is sharp sand, made up of sand, tiny fragments of rock crystal, not soft, "harmless" or "normal" dust.