Visualizing and understanding geologic structures is one of the most challenging tasks facing students in introductory geology courses. In order to comprehend geologic structures, it is necessary to practice your skills at 3-dimensional visualization.

Digital technologies are a marvelous way to illustrate the complex 3-dimensional relationships of strata in geologic structures. A picture may be worth a thousand words, but a good picture of a geologic structure is priceless.

The image below shows Grenville Dome, a small doubly plunging anticline located near Sinclair, Wyoming, USA. This image was generated using a computer to process a digital elevation model (DEM), then a digital aerial image was mapped to the surface to produce this wonderful 3-dimensional image.

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You can imagine the scale of this structure by noting the 4-lane interstate highway in this image just north of the structure. Also, the small town of Sinclair, Wyoming.

The image below is a close-up virtual view of the Grenville Dome. In this image, it is evident that the exposed strata are inclined (dipping away from the center of the structure). Note that the pattern of stream erosion creates v-shaped notches in the outcrops, and the "v" points in the direction of plunge. Which strata do you think are oldest in this view? Which are the youngest? How would you measure the strike of these strata?

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Folds such as this record intervals of geologic time when tremendous tectonic stresses occur within the lithosphere. Folding like this is often associated with large scale mountain building events driven by Plate Tectonic processes. Thorough analyses of folds across a geographic region can yield a good deal of information about the geologic history of that area.

 

Grenville Dome WY Fly By (1841.0K)

Points to Ponder:

1. Print a copy of this page and label the images to show the orientation of tilted strata (strike and dip) around the Grenville Dome.

2. Discuss with your instructor how a structure like the Grenville Dome formed.