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| | Yellowstone National Park - Nature & Science |
 | | At the peak of this glacial era, roughly 25,000 years ago, prominent peaks like Mount Sheridan lay hidden underneath this icy blanket, while the tip of Mount Washburn and the thin ridgeline of the Absaroka Mountains barely peeked above this unrelenting sea of ice. |
 | | Among the broad hills and benches of Hayden Va l l e y, lake sediments of silt, sand, and gravel, covered in glacial till, remain from a time when the valley was covered by an ancient lake formed by an early ice dam. |
 | | Glacial ponds, striated hillsides, chiseled peaks, and polished mountain faces, all fashioned by the hand of ice, create some of the finishing touches on the spectacular landscape we see today. |
| www.nps.gov /archive/yell/pphtml/subnaturalfeatures13.html (431 words) |
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