Alyssa Munch's fourth-grade students at Hawthorn Elementary North in Vernon Hills asked: "Where does quicksand go?"
Quicksand is a mixture of water and sand or air. Instead of forming a fairly solid surface, the mix creates the look of a secure base, but when it is disturbed, it caves and creates suction. Quicksand can occur on river banks, beaches, in places where there are underwater springs or on sand dunes in the desert.
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In times past, another definition for the word "quick" was flowing; quicksand shifts and churns when the surface is disturbed.
"At first sight it looks solid, but when you stand on it, it collapses, pushing out some of the water or air and collapsing into a smaller volume," said Darrel G.F. Long, professor of sedimentology at Canada's Laurentian University in Ontario.
Professor Long has had that sinking feeling from stepping into quicksand.
"I was not expecting it to be there," he said.
He's observed quicksand in a river bed and quicksand volcanoes in a buried spring.
"The central spout of sand formed a small, active fountain with sand streaming sideways from the neck," Long said.
Where does the quicksand go when you plunge your foot into it?
"The sand goes down and the water or air moves up," Professor Long said. "Imagine a house of cards - it looks solid when you stack it up, but when you stamp on the floor next to it the cards fall down into a solid pile and the air between the cards is pushed out."
Quicksand can revert to a more stable surface.
"When the supply of upwards-moving water or air stops, the fabric of the sand collapses and is no longer active. The sand is still there, but it is no longer quick," Professor Long said.
Quicksand has been seen locally at Adeline Jay Geo-Karis Illinois Beach State Park in Zion. The scenic 4,000-acre park along the Lake Michigan shoreline includes sand dunes, the Dead River, a forest and a sand prairie. The source of the quicksand is usually man-made.
"Out here, there can be a water main break and water bubbles up and supports the sand on the surface," said Bob Feffer, Illinois Department of Natural Resources site assistant. "On occasion, the sand can be soft and you can sink into it," he said.
The wide variety of plant life and ecosystems found at the park make it a popular destination for science classes of all ages. For more information, see the park Web site at dnr.state.il.us/lands/Landmgt/PARKS/R2/Ilbeach.htm.
Check these out
The Wauconda Area Library suggests these titles on quicksand:
• "The Boys' Book of Survival: How to Survive Anything, Anywhere," by Guy Campbell
• "The Quicksand Book," by Tomie De Paola