Quicksand

Though quicksand exists in many parts of the world, little was known about its composition until the 20^th Century.

The most popular theory was that quicksand was made up of rounded sand grains. Unlike the jagged grains of ordinary sand, the theory went, the rounded grains acted like miniature ball bearings, rolling with so little friction that any weight, such as a man's, would sink rapidly.

Another theory held the quicksand grains were lubricated with slime or some other slippery sub­stance that made them slide out from under a weight. But no one really knew how quicksand worked.

Our present understanding of the phenomenon of quicksand stems from certain experiences in World War II. Then, during the 1944-45 invasion of Ger­many, Allied armies discovered they needed a lot more knowledge of how to move troops over unstable soils.

The American Army's interest sparked a number of scientific studies of quicksand. One was conducted by Dr. Ernest Rice Smith, geology professor at Indiana's DePauw University. He spent days studying a quick­sand bed in a pasture not far from the university. The bed was near a small stream, and its surface was a mottled yellow-green from the pond slime growing on it. When he threw a rock into it, the sand quivered unpleasantly and seemed almost alive.

What made this sand different from commonplace sands? Smith scooped up a bucketful and later exam­ined samples of the sand under a microscope. The grains turned out to be an ordinary mixture of shapes -some were round but most were jagged. So the round-grain theory was out. The lubricated-grain theory didn't seem to hold up either. Though Smith kept his sample of sand moist and the green algae continued to thrive, the sand wasn't quick any longer. It was just as firm as beach sand.

Back in the pasture, Smith talked to the owner of the farm. "Funny thing about that stuff," the farmer said. "Sometimes it's quick, sometimes it's firm. Come back in August and you'll be able to dance on it."

August-the dry month. Could water be the answer then?

But ordinarily, Dr. Smith knew, moist sand sup­ports weight as well as dry sand. Maybe the answer, Smith reasoned, lay not in the amount of water but in its flow. Where water is just sitting in sand, the sand is not quick. But suppose the water is flowing through it in some peculiar way. . . .

Smith canvassed other geologists and found that many had been speculating along similar lines. To settle the question, Smith and several other scientists built experimental devices in which water could be made to flow through sand in various ways.

One of the most sophisticated models was built by Prof. Jorj Osterberg of Northwestern University. His device was a large tank filled with ordinary sand and equipped with hose connections so that water could be made to flow in at the top and out the bottom, or vice versa. To complete the experiment there was a plastic dummy filled with lead shot so that its specific gravity was roughly the same as a man's - that is, it floated in water, with the top of its head above the surface.

When the sand in Professor Osterberg's tank was dry, the dummy could be placed in standing or lying positions on the surface, barely making a dent in it. When water was poured in from the top, the dummy still would not sink. But when water was forced into the tank from the bottom, welling up through the sand, the dummy sank to its neck. Upwelling water, as from a spring, forces the grains apart slightly, the re­searchers discovered, and makes the sand mass swell. Each grain then rests partly on the cushion of water instead of solely on other grains.

Researchers discovered that some kinds of quicksand are quicker than others. They found that the finer the sand, the slower the upwelling of water that is needed to make it quick. With fine sand and a fast upward flow of water, the result is what soil engineers call a "super-quick" condition. A human being sinks in it immediately, though it may look as firm as concrete. Where the water flow is slow, or the sand grains are coarse, the result is slow quicksand. Someone can take a few steps into it, and usually is still able to turn around and get out.

If a person does not sink immediately in quicksand, and keeps their head, they may be able to float in quick­sand as in water.

Since quicksand obeys the laws gov­erning the displacement of liquids, a body will sink in the stuff only until it displaces its own weight in liquid; then it begins to float. And since quicksand is heavier than water, a person floats more readily in it than in water.

But encounters with quicksand are sought after by no one, including the experts - who recommend possi­ble survival techniques. For all that scientists have learned about the workings of quicksand, its chief fascination still lies in its potential deadliness.

Escaping From Quicksand

An encounter with quicksand is seldom as horrible as it is depicted in stories and movies. But quick­sand pits are found in virtually every part of the world; thus it is possible to stumble on one unknow­ingly.

If you ever get into quicksand and need to escape, try to follow these rules:

1.   First, don't panic. Quick­sand seldom kills its victim.

2.   Second, warn off companions. You might need their help.

3.   Third, get rid of packs and items that can weigh you down.

4.   Fourth, lean backward in a spread-eagle position. This should allow you to float.

Finally, gently squirm or roll your way toward firm ground.

Note:  It is a good idea to carry a pole when walking in sus­pected quicksand areas for use as a rescue aid.