Close encounters with sand and soil can reveal a lot


Born in the Netherlands in 1632, Antony van Leeuwenhoek was a self-taught man who made microscopes — ultimately producing some 500 of them. Microscopes consist of lenses of carefully ground class.

Van Leeuwenhoek’s microscopes could magnify objects up to 200 times. That opened up a range of investigations to him, and he took advantage of the new devices he was creating to look at a variety of subjects, including bacteria he obtained from between his teeth.

Van Leeuwenhoek also took a deep interest in a common substance: sand, which he collected and studied. This may have been because he used sand to grind his microscope lenses.

In any event, using his creative mind and careful observations, he studied sand intensely. At one point he published the following statement: “I have formerly affirmed of Sand, that you cannot find in any quantity whatsoever two Particles thereof that are entirely like each other.” Sand, in other words, is a bit like snowflakes, with individuality built into each particle.

Recently, I was reading about van Leeuwenhoek in a book by Michael Welland called “Sand: The Never-ending Story.” It’s a good read, and I recommend it if you take an interest in the natural world. Even a simple substance like sand can be fascinating from a variety of viewpoints once you learn about it.

For example, sand can be of forensic interest. Sand found in the tire treads of a car or the footwear of a person can place a suspect at the scene of the crime just as effectively as an eyewitness. Sherlock Holmes was, of course, a fictional character, but his methods of observing sand and mud on shoes have the strength of forensic science behind them.

An early case concerning sand and soil as forensic evidence came about in 1908 in Bavaria. The police suspected a man who happened to be a poacher of murdering a woman. Luckily for investigators, the poacher’s wife had cleaned his shoes the day before the murder.

Police found three layers of earth material on the shoes during their investigation. The first layer, nearest the sole of the shoe, corresponded to the earth outside the poacher’s house. No surprises there — he had worn his freshly cleaned shoes when he left his house, and picked up soil on his shoes as soon as he stepped outside.

The next layer of material on the shoes was laced with distinctive red sand, of the sort found where the victim's body had been discovered. The final and outermost layer included cement, brick fragments and coal dust, corresponding to materials on the ground where the poacher’s gun had been found.

Tellingly, none of the layers of material on the suspect’s shoe matched the soil from the fields where the poacher claimed he had been at the time of the murder.

In short, the simple evidence of detritus on his shoes placed the suspect at the crime scenes, bolstering the prosecution’s case just as a witness might have.

Sand is also interesting to physical scientists. It’s a granular material, like salt or sugar. In some ways, dry sand behaves a bit like a liquid. If you pour it into a jar, it takes the shape of its container.

If you make a heap of sand, adding more and more grains to the top of it, at some point you’ll get material to slide off the pile and sometimes flow onto the level surface around the heap of sand, spreading itself out over considerable distances, a bit like a liquid would flow.

You may have heard of the black sands of Iwo Jima, the Pacific island at which a major World War II battle was fought. The sands are composed of volcanic ash from the area. The ash-sand has unusual granular properties.

Welland reports that one Marine who took part in the battle described the sand as so problematic “it was like trying to run in loose coffee grounds.” The granular properties of the special sand made moving on the black beaches quite a chore.

You really can see the world in a grain of sand.

E. Kirsten Peters, Ph.D., a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.


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