http://www.summitpost.org/marcy-s-great-chimney-aka-empty-tomb-all-ryle…

Three rock climbs on Mt. Marcy. Full details above.

One of the best kept backcountry secrets is a large vertical trap dike capped with a diagonal car-sized capstone on Mt. Marcy. It is set in a northeastern facing cliff deep in Panther Gorge and looks like a pencil-thin shadow from the summit of Mt. Haystack. This is Marcy’s Great Chimney.

St. Lawrence University Professor of Geology, Jeff Chiarenzelli, describes the dike as follows, “The dike is composed of basalt, a black, fine-grained rock that often erupts on the surface or is found in feeder dikes to volcanic rocks. Similar basaltic dikes are found throughout the Adirondack region and are approximately 640 million years old. Produced in the Earth’s mantle they intruded into cracks and fractures as the eastern seaboard was rifted apart to form the Iapetus Ocean. The Iapetus Ocean formed during the cycle of continental breakup prior to the opening of the Atlantic.” The basalt in the dike is lighter from weathering. Basalt also differentiates Marcy’s dike from Colden’s whose primary trap rock is gabbro which has larger crystals.

The basalt eroded and formed several vertical to slightly overhanging sections in a deeply inset six-foot wide chimney—the chimney is what originally drew my attention. Unlike Mt. Colden’s Trap Dike which is generally considered a fourth class climb, Mt. Marcy’s dike is a fifth class rock climb rated 5. It is worth the effort of visiting.