Cold "snaps"

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Quad Cities (KWQC) - Creeks and cracks abound, today, thanks to the quick drop in temperatures. As buildings get cold the materials that make them contract. Since materials of differing densities will contract at different rates, stress can build up between the joints of most structures. When that stress is released you can, many times, easily hear it if you're in the building that's contracting. Sitting in our studio as I type this I can hear our KWQC building making moves in the 5 degree outside air. And outside it's a matter of Cryoseisms, or "Frost-Quakes"! This is when the cold air causes the ground to expand and shift as water in the soil freezes leading to loud bangs or thuds that, again, you can hear if you're near the point or origin. A bit creepy sounding, they are the result of the perfect conditions that set up early Saturday. There are four main ingredients for a "frost quake" to occur. A very cold air mass must settle over an area. The ground must saturate from rain prior to a cold air mass arriving. Ground can be bare, or even a little snow covered, but not so snow-covered as to cause insulation from the cold air. Then, within 16 to 48 hours, a rapid chill down to 0 or below must occur. As the water saturated in the top layers of soil freezes, the ground expands and pushes against itself. After a build up of pressure the resulting release, once again, can cause loud noises like thuds and booms that you can hear if you're near the point of origin. It's not difficult to hear because this happens near the surface of the ground. If these sounds creep you out you might want to put your earmuffs on. They might keep you from hearing the "pops" and, since it's so cold in the first place, the warmth will prove comforting!