The Geology of Virginia's Blue Ridge
 
    

F O R   S T U D E N T S   &   T E A C H E R S

The rocks in the Blue Ridge 
mountains of Virginia, range in age 
 from 250 million years to one billion years old


In Virginia, the oldest rocks in the Blue Ridge province are different types of granite which date back over one billion (1,200,000,000) years. Some of the rocks in the Blue Ridge were there before there was even life on Earth! Younger rocks from the Paleozoic era cover the eastern side of the Blue Ridge. The rocks that make up the Blue Ridge have been shoved over the rock layers of its neighbor to the west A, the Valley & Ridge province. The rocks were moved to the northwest when (what today is) Africa and North America got sandwiched together, pushing the Blue Ridge on top of the Valley & Ridge along a fault line. By being deformed, older igneous and metamorphic rocks show that the continents crunched together and split apart many times during the Paleozoic.

Sedimentary rocks from 750 - 700 million years ago can help tell us they were formed at a time when Africa was ripping away from Virginia. The gap formed between the two spreading continents is known as the Iapetus Ocean. In Roman mythology, Iapetus was the father of Atlas. Atlas is the namesake for today's Atlantic Ocean. In areas of central and northern Virginia Blue Ridge, greenstone (metamorphosed lava flows) 570 million years-old can be found above many of these sedimentary and metamorphosed sedimentary layers.

Early in the Cambrian, when the Iapetus Ocean opened, the sea level rose, moving the beached inland. The sandstones from these beaches are preserved in the Chilhowee group. As sea level continued to rise throughout the Ordovician, carbonate rocks in the shallow seas, such as limestone and dolomite, were deposited.

In central and northern Virginia the Blue Ridge mountains rise to elevations over 1200 meters (4000 feet). The local relief (difference in height) on the east side of the Blue Ridge is up to 1000 meters. In the southern Blue Ridge of Virginia, a broad table-like region rises over 500 meters above the Piedmont province. Mt. Rogers in the southwestern Virginia Blue Ridge, at 1746 meters, is the highest peak in Virginia.

 
      

    
APPALACHIAN PLATEAU | VALLEY & RIDGE | BLUE RIDGE | PIEDMONT |COASTAL PLAIN
 
 

(11/4/98)
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