By Ed Curran

CHICAGO (CBS)– A 12-year old girl died after becoming trapped in a snow fort while playing in the snowbanks outside an Arlington Heights church Sunday afternoon.

The medical examiner reported Esther Jung suffocated and her body temperature dropped fatally low. A 9-year-old was treated for hypothermia and is expected to recover.

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Jung’s death reveals an often overlooked danger with snow, it’s weight.

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CBS 2’s Ed Curran explained when snow is compacted in huge piles, the weight becomes unbelievable.

Freshly fallen snow is heavy, about 12.5 pounds-per-cubic-foot and 25 cubic feet weighs over 300 pounds, depending on the moisture content.

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Compacted snow can more than double that weight, 25 cubic feet of packed snow can total more than 700 pounds. Curran said that is why compacted snow is especially dangerous, whether it’s piled up in a mountain avalanche or by a parking lot plow.