Where on Earth? - December 2010

Clues for December 2010:
1. Thousands of years of freezing and thawing cycles during the last ice age broke a nearby rock formation into these large chunks of red sandstone and conglomerate, which are strewn across a relatively flat valley. These stones, ranging in size from 1 meter across to more than 8 meters across, have remained in this valley, relatively unchanged, for more than 20,000 years.
2. A nearby terminal moraine marks the southernmost extent of the Wisconsinan ice sheet to the north and east of the valley, and provided a clue that periglacial activity was responsible for the field of stones.
3. The site is a designated national natural landmark, one of about 600 geologic or biotic features in its host country with that designation.
Name this feature and its location.
Scroll down for the answer
Answer: Boulder Field, in the northeastern corner of Pennsylvania’s Hickory Run State Park, is a jumble of large chunks of red sandstone and conglomerate. The stones are identical to rocks atop the nearby ridges surrounding the field, and likely formed due to freezing and thawing cycles during the last glaciation. Photo is by Christopher S. Schiappa.
December winners
Thom Davis (Campton, N.H.)
David Hochman (Marlboro, N.J.)
Kenneth Long (New Holland, Pa.)
Susan Millar (Syracuse, N.Y.)
Noel Potter (York Springs, Pa.)
Penny Robitaille (Bel Air, Md.)
Daniel P. Roll (Gansevoort, N.Y.)
UPenn Geology 103 class (Philadelphia, Pa.)
Jay Smerekanicz (New Boston, N.H.)
William J. Wayne (Lincoln, Neb.)

To submit your photographs to our Where on Earth? contest, send them via e-mail to

01 Dec 2010