Geology of New England
Most of New England consists geologically of volcanic island arcs that accreted onto the eastern edge of the Laurentian Craton in prehistoric times.
The bedrock geology of New England was heavily influenced by various tectonic events that have occurred since the Paleozoic Era including the accretion of land masses that formed various continental terranes to the Mesozoic rifting of the Hartford Basin.
Laurentia is believed to have originated at the end of the Hadean, making it one of the oldest regions with continental crust, as evidenced by the discovery of Acasta Gneiss in Canada.
Starting in the Paleozoic Era the supercontinent Pannotia began to break up, forming smaller continents including Laurentia (North America and Greenland), Gondwana, Baltica, and Siberia.
[2] During the Middle Ordovician period of the Taconic orogeny, volcanic island arcs collided with the eastern coast of North America, causing extensive metamorphism, faulting, and uplift.
Following the subduction of the Iapetus Ocean floor, the microcontinent Avalonia slammed into eastern North America, which caused another period of metamorphism, faulting, and mountain building.
The Littleton Formation was deposited in the Early Devonian, approximately 409 million years ago with a Gander and/or Avalon Terrane source.
[8] Volcanic formation in the White Mountains has been estimated to have occurred between the late Jurassic and early Cretaceous periods, and would have coincided with the separation of Pangaea.
[8] As Pangaea broke apart and land masses were shifting, large features like the White Mountains were formed; at the same time, as this multitude of cracks was occurring, magma rose up and filled many of these voids.
The Ossipee Mountains contain substantial amounts of volcanic rock, and the many ring dikes across the region indicate that there was once an active volcano on the site.
[9][10] Volcanic rocks can also be found throughout the White Mountains beyond the Ossipee region, further confirming that eruptions occurred across the area millions of years ago.
Large terminal moraines composed of poorly sorted till are present along coasts and can be identified by their thin, patchy, and stony texture.
[12] New England is best known for its high density of erratics, which are displaced rocks that differ from the immediate bedrock composition of the region and range from the size of pebbles to boulders.
Glacial striations help determine the direction of a glacier; visible outcrops in the White Mountains, for instance, indicate ice flow toward the south-southeast.
Cosmogenic Nuclides are radioactive isotopes formed when high-energy particles (i.e. cosmic rays) interact with the nuclei of Solar System atoms.
[17] A group of geologists in New England have been using an age-exposure method called the 'Dipstick' Approach, which can determine the rates of ice-sheet thinning and the age of glacially eroded boulder and bedrock surfaces.
[18] Following the glacial melting of the Laurentide Ice Sheet, new vegetation and warmer climate caused new New England to become inhabitable by early human settlers.
This new climate, combined with an ample supply of hard volcanic rock and other natural features, created an ideal area for human settlement.
The melting of the Laurentide Ice Sheet (beginning by 18,000 cal yr BP) caused significant ecological and climatic change in the region.
