Mt. Moosilauke (300 MYBP) - Formation
". . . The geology of Mt. Moosilauke can best be understood in the context of the geologic history of New Hampshire and Northern New England. The proto-Atlantic ocean disappeared in the middle Devonian period (300 million years ago) as the land masses collided. This collisional event has been named the Acadian orogeny and is similar to that going on now between India and Asia. Along the collision zone, mountains like the Himalayas, were pushed up. The collision was accompanied by extreme folding of the volcanics and the sediments.
Although some sediments and rocks are pushed up in a continental collision, some are also pushed down and buried deeply. With increasing depth of burial, and, therefore, increasing temperature, minerals in sand,mud and volcanics become unstable and recrystallize as new minerals that are stable under the more extreme conditions. The light gray quartz "sand" is still mostly quartz, but dark gray "clay," metamorphosed into schist, now includes mica, garnet, and sillimanite (alumino-silicate). These minerals indicate that these rocks were buried approximately seven miles deep and subjected to temperatures around 550 degrees Centigrade. Sillimanite-bearing rocks are very resistant to erosion which is why the Littleton Formation holds up high topography including, besides Moosilauke, New Hampshire's highest peak, Mt. Washington. . . ."
From "The Geology of Mt. Moosilauke and Environs" by MaryAnn Love Malinconico, pp. 1-12, The Moosilaukee Reader (Vol.1). ©1999.
