Patty Henderson, age 10, of Charlotte, N.C., for her question:
ARE THE WORLD'S OLDEST MOUNTAINS IN NORTH CAROLINA?
The beauteous Blue Ridge Mountains step gracefully down to the Eastern shore. Here and there the woodsy slopes dip their toes in streams and sparkling lakes. The mountains that formed this gentle geography of North Carolina began to grow more than 200 million years ago. They are very old but not the world's oldest.
North Carolina's mountains belong to the mighty Appalachian Range. Actually this mountain chain is a huge ridge of many ropy ranges, running along the Atlantic Coast from Quebec to Alabama. It is the oldest mountain chain that still stands proud and tall in North America. But the mountains of Greenland are older. And even in North America the worn down roots of much older mountains still remain as gentle hills.
The great Appalachians have a northern and a southern arm. The northern ranges poked up their peaks about 300 million years ago, when the first plants and animals left the sea to live on the dry land. Their ranges reach through New England to southern Canada. More than 100 million years later, the southern arm of the Appalachians began to grow. They formed the Great Smokies, the Blue Ridge and all the other scenic beauty of North Carolina.
A mountain range is an enormous ridge in the earth's crust, and enormous energy is needed to build it. Great crustal slabs of rock were uplifted, bent and cracked and stacked like jumbled, giant size sandwiches. Volcanos helped to push and erupted lava helped to build the peaks higher. It takes more than 100 million years to build a mountain range.
Even before the massive job is finished, the weather begins to wear down the mountain's lofty peaks. This, too, takes endless ages. After a few hundred million years, the once tall range is a region of gentle hills.
The restless earth is very old, and its original crust has been remodeled many times. Maybe its first mountains have been lost. But in Minnesota there are the remains of mountains that formed half a billion years ago. And the oldest worn down mountains in the world are the Laurentians of Canada. They were tall, proud peaks 2 billion years ago.