North Carolina Geologic History

1. North Carolina Geologic History Text pages 14-15, Chapter 11A

2. Formation of southern Appalachians • Before the ancient North Atlantic was closed during the formation of Pangaea, the shoreline of NC was where the Blue Ridge Mountains are today. • As North America and Africa moved toward ea. other, a smaller continental fragment between them collided w/N Am. • Compression forced part of this micro-continent up & over the existing N Am rocks, forming the Blue Ridge/Western Piedmont.

3. Carolina Slate Belt/Eastern Piedmont • Parts of the seafloor and a volcanic island arc collided with North America, forming the Piedmont base. • Years of compression caused more folding and thrusting of rock, the Valley and Ridge Province.

4. Converging to Diverging Boundary? • As Africa and North American began to split apart, the Atlantic started to form. • Rivers formed the Coastal Plain by deposition, of sediment (sand, clay, and limestone) carried from the mountains. • Erosion shaped the Piedmont. These hills are made of harder rock (west to east; metamorphic gneiss & schist, igneous granite, sedimentary). See page 6.

5. Drift Phase of Walt Brown’s Hydroplate Theory • “As the Mid-Atlantic Ridge began to rise, the granite hydroplates began to slide downhill on the steepening slopes. Continental plates accelerated away from the widening Atlantic. • The hydroplates ran into resistances of two types; the water lubricant beneath each sliding plate was depleted, and as each massive hydroplate decelerated, it experienced a gigantic compressional event—buckling, crushing, and thickening each plate. Mountains were quickly squeezed up.”