The basalt crystallized quickly against the relatively cold granite. The basalt came from deep within the earth as a fluid material, and because of pressure, was able to force the Conway granite aside. Sometime after the fractures were formed, small dikes of basalt were forced up along the fractures. As it cooled, the granite was broken by closely spaced vertical fractures that lay nearly parallel in a northeasterly direction. Nearly 200 million years ago in the Jurassic period, the Conway granite that forms the walls of the Flume was deeply buried molten rock.

Discovered in 1808 by 93-year-old 'Aunt' Jess Guernsey, the Flume is now a paid attraction that allows visitors to walk through it from May 10 to October 20. Cut by Flume Brook, the gorge features walls of Conway granite that rise to a height of 70 to 90 ft (21 to 27 m) and are 12 to 20 ft (3.7 to 6.1 m) apart. The Flume Gorge (locally, just The Flume) is a natural gorge extending 800 ft (240 m) horizontally at the base of Mount Liberty in Franconia Notch State Park, New Hampshire, United States. Please help to improve this article by introducing more precise citations. This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations.

Flume gorge