Physical Geology of Mount Katahdin: September 2014

The Penobscot Indians must have been justifiably impressed when their ancestors first laid eyes on Mt. Katahdin, so much so in fact, they named it simply "Katahdin", which translates to "The Greatest Mountain". A five peaked laccolith formed from a granite intrusion in the Early Devonian era, nearly 400 million years ago by molten rock which cooled and hardened about two miles below the surface. Through hundreds of millions of years of orogenesis and then weathering, the huge massif finally broke through the cold top layers of New England soil. This massive weathering campaign was aided by glacial deterioration, as evidenced by the abundance of clues left to us from the icy giants, from the ponds, to the aretes and cirques.

Here, we can see a great view of Mt. Katahdin and the surrounding area. Take note of the geographic features that formed secondary to the mountain itself, i.e. the basins and ponds surrounding Katahdin.

http://written-in-stone-seen-through-my-lens.blogspot.com/2014/03/climbing-geology-and-tectonics-of.html

Mt. Katahdin sits about halfway between the east and west borders of the North American Tectonic Plate(the eastern half anyways), which means that while earthquakes do happen, more often than thought most of them go unnoticed or are very mild (the strongest quake reported in Maine occurred in 1904 and had a magnitude of 5.0). While the plate shifts slowly at about 1cm a year, small releases in the built up pressure result in the quakes.

A view of the North American Plate (in brown) in relationship to the rest of the worlds tectonic plates.

http://pubs.usgs.gov/gip/dynamic/slabs.html

Over all of Mt. Katahdin and its five peaks you will notice an abundance of multi-sized granite boulders which appear to have been split by Zeus himself. However, due to the thankless nature of the task, we can draw the conclusion that these were victims of freeze-thaw. A natural phenomenon in which water finds its ways into tiny fractures or void spaces inside the rock, then freezes when temperature plummet, causing the water to expand, and therefore break or split it open. This process happening repeatedly over millions of years has for split some rocks maybe thousands of times over, resulting in miles of jagged granite stones, much like seen below.

Here is a great example of "freeze-thaw", notice how some edges are very geometric or angular, this can lead to serious injuries to climbers and local fauna alike.