Geodynamics
The cause of this great period of deformation is a result of the plate-docking of a small continental landmass called Avalonia (named after the Avalon Peninsula of Newfoundland). The docking of Avalonia onto the composite margin of Ganderia and Laurentia resulted in the closing of a portion of the Rheic Ocean.
Avalonia was gradually torn apart as plate tectonic forces accreted the landmass onto the edge of the larger North American continent. Today, portions of the ancient Avalonia landmass occur in scattered outcrop belts along the eastern margin of North America. One belt occurs in Newfoundland, another forms the bedrock of much of the coastal region of New England from eastern Connecticut to northern Maine.
A period of lithospheric thinning that followed the Acadian orogeny created volcanoes, such as the large Mount Pleasant Caldera in southwestern New Brunswick, Canada.
Read more about this topic: Acadian Orogeny