Plate Tectonics is the vast, complex and overriding process responsible for the geology of the crust of our planet Earth. Our present continents are the emergent portions of plates that slowly (mm/year) migrate across the globe driven by immense thermal convection currents in the partially molten material of the upper mantle. The plates split, move apart, or conversely collide, and are driven over or under neighbouring plates. As plates collide the rocks involved undergo tremendous heat and pressure and are often physically broken, folded and deformed. Furthermore the rocks can, at elevated temperatures and pressures, undergo both mineralogical and fabric changes (metamorphosis) resulting in a class of rocks called metamorphic rocks. Collision events often resuIt in mountain building that takes place over a long but defined period of time. Such times are referred to by geologists as orogenies. It is at deeper levels at plate boundaries during orogenic periods where granite is typically formed.
The rocks that make up Owls Head, Bear Mountain, Sugarloaf and Orford are volcanic and interspersed deep-sea sedimentary rocks that have been metamorphosed during the Taconic Orogeny 450-470 Ma ago). These have subsequently been intruded by granitic magmas towards the end of the Acadian Orogeny (360-390 Ma ago).
