|      In the small    town of Eden, N.Y., the recent appearance of mysterious    circles in a frozen pond has residents    baffled. Last Friday, during an    early spring snowstorm, Eden resident Peggy Gervase    was looking at the pond near her home when she noticed an unusual pattern in    the snow covering the water's surface: large circles that resembled giant    polka dots. "I've never seen    this before in our pond," Gervase told    local TV station WGRZ. "It's eerie in a way, but cool in a way." After Gervase posted a    photograph of the pond circles to the station's Facebook    page, respondents offered a number of explanations for the strange circles, including elephant footprints, fish    flatulence and aliens. Though aliens sometimes    get the blame for crop circles and other unusual phenomenon, with no real    evidence, Gervase isn't buying it. "I'm not that far gone yet," she    told WGRZ. There are more rational    explanations: Natural springs often feed ponds with slightly warmer water    than the water freezing at the pond's surface during cold weather. As the    warmer spring water rises, it would melt the snow and ice on the pond's    surface. Additionally, decaying    vegetation on the bottom of the pond could release gases that slowly rise to    the surface, creating the polka-dot effect. Intriguing circular    formations are known to occur throughout the natural world during seasonal    freeze and thaw cycles. In areas of permafrost    (like the northern Canadian tundra), the expansion of ice beneath the soil    surface — a process called frost heaving — creates raised landforms called    lithalsas. Lithalsas often form circular or ring-shaped patterns on the    surface. Frost heaving also    creates a related landform called a pingo. Over many years, pingos can grow    into small, circular hills: The tallest known pingo is the Kadleroshilik    Pingo in Alaska, which reaches 178 feet (54 meters) in height. Copyright    2013 LiveScience, a TechMediaNetwork company. All rights reserved. This    material may not be published, broadcast, rewritten or redistributed.  |    
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