June 28, 2017

Valleys and Ridges: Understanding the Geologic Structures in Central Virginia Pt.1

Posted by larryohanlon

Sometimes you have to build the field in the laboratory (or in this post’s case, in the art museum). At the Virginia Tech Active Tectonics and Geomorphology Lab they do just that. This is the latest in a series of posts shared from their blog. More of their posts can be found here.

(Words by Lisa Whalen, Video by Phil Prince)

In this first part of a four part series, Dr. Phil Prince explains why we get the valleys and ridges that are the namesake of the Valley and Ridge province of Virginia.

Valleys and ridges can result from the erosion of anticlines and synclines. Knowing the ages of the rock layers can help determine, which you’re looking at when the topographic profiles have been worn away through time.

When rock strata are folded and produce an anticline, or “positive topography,” if then worn down from the top, older rocks will be exposed in the center. The opposite is true for a syncline.


Illustration by Vidimus78

Notice in the cartoon above that the original anticline and syncline are not expressed topographically. Instead two parallel ridges are present where the yellow, and presumably less-erodible strata intersect with the surface.

In this first video we get to see how geologic information overlaid in Google Earth can help illustrate this concept.

Part 2 Coming Soon!

Also see the Seneca Rocks field trip series for more information

This post was originally posted on The Geo Models blog.