Virtual Vista: Stone Mountain, DeKalb County, Georgia, USA

Stone Mountain is one of a number of small igneous plutons that intrude the Georgia Piedmont. Owing to the resistance of the granitic intrusions to weathering processes (to be discussed in Chapter 5) relative to the surrounding metamorphic and sedimentary rocks of the piedmont, these small intrusions remain as other rocks are eroded around their base.

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The result of this process is an isolated, small mountain among the rolling countryside. Stone Mountain rises 250 meters (825 feet) above the surrounding piedmont surface. The granitic magma comprising the mountain was intruded beneath Earth's surface approximately 300 million years ago during the final stages of assembly of the supercontinent Pangea (about which you will learn more in Chapter 19).

Stone Mountain is slowly eroding through a mechanical weathering process called exfoliation. Extensive fractures form parallel to the mountain's surface (sheet cracks) and these will eventually separate and slide off the mountain as onion-like layers. Exfoliation is a common process of weathering observed in granitic rocks.

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Like many unique geological features of Earth, the remarkable occurrence of Stone Mountain has attracted human visitors for centuries. Presently, Stone Mountain is the site of a Georgia state recreation facility offering a variety of entertainment opportunities. A bas-relief memorial to Confederate soldiers is carved into the mountain's side. You may also ride a scenic train around the mountain, hike to the summit on trails, or ride a cable car to the top.

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The images of this Virtual Vista were generated from an aerial photograph of Stone Mountain that was mapped to a digital elevation model of the mountain and its surrounding countryside. The image was enhanced by addition of a sunset scene and virtual lighting effects to create a landscape that looks remarkably realistic. It is evident from these views why the mountain is a source of fascination.

Stone Mountain Fly By (2590.0K)

Points to Ponder:

1. How long do you think it will take for Stone Mountain to erode completely?

2. Assuming Stone Mountain has a hemispherical shape, calculate the volume of Stone Mountain.

3. If Stone Mountain has a density of 2.7 grams per cubic centimeter, how many tons does it weigh?