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ShareJune 1, 2006 — At San Francisco's Exploratorium, a scaled-down model of the city made with Jell-O helps visitors visualize how the city would shake during a major earthquake. In another display, a bowl filled with wet sand and a mallet shows how shockwaves can cause soil to liquefy, swallowing buildings like quicksand -- a grave threat for many San Francisco neighborhoods that were built on sandy landfill.
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SAN FRANCISCO--It's an unusual event ... A meeting of art and science. But it can make for a "shaky" learning experience, especially when it comes to earthquakes.
Artist Liz Hickok shows off her scale model of the nation's shakiest city, San Francisco. It really rocks and rolls because it's made of -- of all things -- Jell-O.
"It's also intended to help us realize that the world we live in and the buildings around us are not as permanent as we might think," Hickok tells DBIS.
Using satellite images, Hickok studies structures like the palace of fine arts and then makes replicas. A table on rollers makes them shake. Hickok says with the shaking, you can kind of get a much more visceral sense of what might happen.
"It's a great segue into science," says geologist Eric Muller, of San Francisco's Exploratorium. Using a bowl filled with wet sand and a mallet, he shows how a quake topples buildings. Many San Francisco structures are built on landfills, areas that used to be water. The sandy sediment is unstable.
"If you send a shockwave through the sediments, it can liquefy and tumble structures over," he says.
Just like packing material in a box, when the sand is shaken, its volume decreases. "And the water rises to the surface, liquefying the surface. You can have a great building, but if the foundation underneath you starts turning into mush, there's not a whole lot you can do," Muller says.
That was one of the factors that contributed to San Francisco's damage after the great earthquake in 1906. This exhibit gives students a sense of what it was like ... And what could happen again.
BACKGROUND: Using satellite images for an initial design, artist Liz Hickok built a scale model of San Francisco using nothing but molded Jell-O, which was featured at the Exploratorium Science Museum. The jiggling mini-city was mounted on plexiglass and placed on a shake table to simulate what happens to buildings during an earthquake. Specifically, it demonstrates liquefaction: when the tremors pressurize the water in soil underneath a building.
WHAT IS GELATIN? Gelatin is a processed protein called collagen, derived from the bones, hooves and connective tissues of cows or pigs. Those parts are ground up and mixed with acid or other chemicals to break down the cellular structure, thereby releasing the collagen. Boiling it causes a layer of gelatin to form on the top, which can be skimmed off for further processing. Eventually it ends up in your local grocery store aisle in powder form.
WHY IS JELLO LIKE DNA? Different proteins have different structures. Gelatin's structure is similar to DNA, except where DNA has two chains twisted together into a helix, the proteins that make up gelatin have three chains of amino acids tightly bonded together. The only thing that breaks those bonds is energy. Boiling water adds a great deal of energy, in the form of heat, sufficient to cause the three strands of amino acids in collagen to unwind. As gelatin cools, the chains start bonding again.
WHY IT GELS: Because it takes so long to cool, the amino acid chains become entangled as the mixture is stirred, and water gets into gaps between the chains. You can add ice so the gelatin will set more quickly, but it is never quite as firm as that produced by the slow-set method. The various molecules cool so quickly that they can't self-organize in the most efficient and strongest bonds possible; instead, only a loose matrix forms. If the energy levels of the requisite molecules are lowered more gradually, as in the slow-setting method, they have more time to align properly, forming a much denser lattice structure, trapping the mixture of sugar, pigments and water in between the strands of amino acids.
The Incorporated Research Institutions for Seismology, Inc. contributed to the information contained in the TV portion of this report.
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