New England has a complex geologic history and, like much of the western U.S., was pieced together by a series of exotic terrains. At the beginning of the Ordovician Period, the east coast of the region was west of what is now the Hudson Valley; then, about 450 million years ago (MYA), an elongated island chain collided with the Northeast coast, adding much of western New England and a large portion of the Canadian Maritime Provinces. This collision initiated the Taconic Orogeny, uplifting a range of mountains from northeast Canada to present-day Virginia.
Fifty million years later, the Avalon Subcontinent, which sat in the northern Iaepetus Ocean, between the North American and European Continents, slammed into New England, adding coastal New England, Nova Scotia and the Avalon Peninsula of Newfoundland; its northeast segment would become northern France and the British Isles. The collision of Avalon with North America triggered the Acadian Orogeny, raising mountains where the Northern Appalachians now stand.
By the end of the Devonian Period, some 350 MYA, these ancestral ranges had nearly eroded to the surface but a new, more extensive Orogeny would soon take place. Throughout the Carboniferous Period, the age of extensive fern forests, giant amphibians and primitive reptiles, the Iaepetus Ocean continued to close, drawing Africa and North America together. The eventual collision of these Continents (320-250 MYA) would produce the Appalachian Orogeny, lifting a continuous chain of mountains from eastern Canada to eastern Oklahoma; these are now known as the Appalachian Mountains (from New England to Alabama) and the Ouachitas (west of the Mississippi Valley). Initially resembling the modern Rockies and Alps, these older mountains have since eroded into lower summits which, except in northern New England, are rounded off and covered by forest.
