At the time the rocks of the Blue Ridge Mountains were being thrust up by tremendous forces that slowly squeezed the rocks of the region very much like a huge vise, other natural processes of weathering and erosion started tearing down the young mountains. Now, after more than 250 million years have passed, mountain building has ended and erosion has gradually stripped off the uppermost miles of rocks that were originally here. In the process, rocks that were once buried and squeezed under the weight of miles of rock are now exposed at the top of the Blue Ridge Mountains where we see them at The Blowing Rock and other areas in this region.
These old rocks were drastically changed (metamorphosed) by high pressure and temperature during the hundreds of millions of years while they were still buried. Geologists have classified these metamorphic rocks as GNEISS (pronounced “nice”). The age of the gneiss has been determined to be 1,055 million years by the geologists of the U.S. Geological Survey. This age is based on the amount of radioactivity still present in the small crystals of the mineral zircon found in the rock. This particular rock is officially designated THE BLOWING ROCK GNEISS by Geological Survey of The United States.
During the formation of the Blue Ridge Mountains, strong pressure in the rocks of the earth’s crust produced many features which we now see at The Blowing Rock. These features include the more or less “striped” appearance caused by the alignment of the crystals of minerals in the rock. The pressure also caused many microscopic cracks in the rock. Weathering has widened and enlarged these cracks. Erosion by running water has removed the weathered material to such an extent that the present form of The Blowing Rock has been created.