The land in northeastern Alabama is composed of terranes, discrete fragments of crust accreted on to a craton. Terrane accretion is one mechanism by which continents grow.

Three major tectonic events molded the Cheaha State Park area into what it is today.

• The Taconic Orogeny took place in the Ordivician Period (about 420 million years ago). The North American and European tectonic plates collided, producing an equivalent mountain building event in Europe at the same time. The Piedmont Terrane was added to the continent during this event.
• The Acadian Orogeny occurred in the Devonian and Silurian Periods (about 350 MA). This event did not produce the faulting and thrusting seen with the other two orogenies. Instead, it left behind granites of that age, similar to the Andes and Cascade mountain ranges.
• The last mountain building event was the Alleghanian Orogeny, which happened in the Permian and Carboniferous Periods (about 250 MA). The Carolina Slate Belt was pasted onto the continent during the Alleghanian Orogeny.

There is a compositional change between the Carolina and Piedmont Terranes, which are separated by a boundary called a suture.

back to opening page