Mt. Katahdin
       7 ½’ quadrangle: Mt. Katahdin, ME
       Piscataquis County
       Baxter State Park
       Northern terminus of Appalachian Trail

Intrusive
5,267 ft (1,605 m)

Katahdin from the south. The Appalachian Trail approaches from the left. (PJT 1978)

View toward summit along Appalachian Trail. Note what Thoreau called a "cloud factory" at head of valley. (PJT 1971)

Bedrock: Katahdin Granite

Devonian +/- 360 my

Pink to gray, medium-grained biotite granite. The pinker phase occurs at the summit, and the gray phase toward the base. The rock at higher elevations also contains more miarolitic cavities, suggesting that it solidified closer to the earth’s surface. Katahdin is one of the few plutons in New England with apparently associated volcanic rocks of similar composition and age, in this case the Traveler rhyolite tuff and lava exposed on Traveler Mountain north of Katahdin.

Surficial Geology: Katahdin’s expansive tableland is strewn by lichen-covered frost-shattered granite blocks, some of which people have piled into a cairn at the summit to achieve a height of 5280 feet above sea level. Directly north of the summit one peers straight down into the Great Basin, a glacial cirque containing Chimney Pond, a tarn about 2000 feet below, while the Knife Edge leads off toward the east. Valley-glacier moraines and other ponds are preserved downstream from the tarn. Beyond the Great Basin cirque is another sharp ridge, Hamlin Ridge, technically an arête because it separates this basin from another cirque, the North Basin.

Unlike Mt. Washington, NH, it appears that Katahdin did host valley glaciers on its flanks after the continental glaciers receded. However, some geologists have presented evidence that indicates the cirques formed during an interglacial period, before the last advance of continental ice. Moraines left by the waning continental ice sheet, eskers, and erratics can be seen at lower elevations.

Additional Photos:

Selected References:

• Caldwell, Dabney W., 1972, The Geology of Baxter State Park and Mt. Katahdin: Maine Geological Survey Bulletin No.12, Dept. of Forestry, Augusta, 57p., one plate
• Hon, Rudolf, 1980, "Geology and petrology of igneous bodies within the Katahdin pluton" Trip A-2, p.65-79 in Roy, D.C. and R.S. Naylor, editors, Guidebook to the Geology of Northeastern Maine and Neighboring New Brunswick, New England Intercollegiate Geological Conference, 72nd Annual Meeting, Boston College Press.
• Waitt, R.B. and P.T. Davis, 1988, No evidence for post-icesheet cirque glaciation in New England: American Journal of Science, v.288, no.5, p.495-533

Other suggested sources of information:

• Glossary: http://www2.nature.nps.gov/geology/usgsnps/misc/glossaryAtoC.html
• Time scale: http://www.ucmp.berkeley.edu/help/timeform.html
• Maine Geological Survey: http://www.state.me.us/doc/nrimc/mgs/mgs.htm