Wandering with Ancient Rocks

One of the really fun things here is to watch the roadsides tell the story of how this area has been transformed by time and geologic activity. Not unlike the Canadian Maritimes, the rocks are ancient, bent and weathered stones that began most of their development during the earliest geologic periods.




It was some 400 million years ago when the Iapetus Ocean started to close bringing Canada, New England and the Baltics together to form the Appalachians. The White and Green Mountains formed 200 million years after that when volcanic hot spots passed under the bedrock and pushed up mountains higher than the Rockies. Volcanism heated the rocks and caused bending and folding of layers that can be seen from cuts in the roadside.


You can see these now rounded Batholiths or plutons--large masses of intrusive igneous rock believed to have solidified deep within the earth—just about everywhere. Now, after the ice ages have passed, the once high sharp peaks are rounder, feminine mountains that welcome meadows, lakes and streams between their heights.















Not far away in Franconia Notch State Park, NH, we visited The Flume where the rocks were split by a rise in volcanic lava that stopped just below the surface some 200 million years ago. Over time and through the grinding during the glaciation, the softer lava was exposed and slowly washed away leaving the deep rift in the rocks. The rift is now a wonderful gorge where one can walk and wait silently with the ancient exposed rocks.










This region was entirely covered by a large continental glacier known as the Laurentide ice sheet, which reached its maximum size about 24,000 years ago. This was the most recent of several ice sheets that spread over the area during the Pleistocene Epoch (about 1.8 million to 10,000 years ago).

Ice age animation http://www.museum.state.il.us/exhibits/ice_ages/index.html

The ice sheets stretched from Long Island back to its source areas in central Quebec and the eastern Hudson Bay Lowland and it buried the highest peaks of the Green Mountains of Vermont, the Adirondacks of New York, and the White Mountains of New Hampshire. When the ice was at its maximum extent, world-wide sea level was about 400 feet lower than it is today due to the massive amount of water locked up in glacial ice around the world. In glaciated regions the tremendous weight of the ice depressed the land underneath by as much as 2,300 feet. In this part of Vermont and New Hampshire, the land surface was depressed about 800 feet and mild earthquakes are sometimes felt as the land still springing back from the release of ice.

The lowland meadows and riverbeds are filled with eroded bedrock, and glacial scour from movement of the glaciers. Glacial till in the Danville/St. Johnsbury areas give an indication of the bedrock types that the glacier has overridden during its journey down from the north. Although this glacial ice moved from northern Canada, most of the stones are from less than 10 or 20 miles away, with only a very small fraction having moved more than 40 miles. Climate rapidly warmed and the ice sheet responded by thinning and retreating to the north leaving most of Vermont ice-free by approximately 14,000 years ago. The beautiful evidence of the icy work is still visible today in the smoothed rock faces, sharp escarpments and flat meadows.