Blue Ridge Physiography Topics

1. Regional Setting
2. Extent and Boundaries
3. Characteristic Features
4.  Drainage
5. Special Features
• Introduction to Physiography
Coastal Plain
Mesozoic Basins
Blue Ridge
Valley and Ridge
Appalachian Plateaus
Virginia's Rivers

Blue Ridge Physiography: Drainage (Part 2)

Stream Piracy and "Wind Gaps"

• The Northern Blue Ridge provides very good examples of stream piracy. Because of stream piracy, many former water gaps have been converted into "wind" gaps.

natural diversion of the headwaters of one srteam into the channel of another

• These wind gaps are seen as low points in the Blue Ridge that serve as places where people can cross the mountains. Today, roads are built through the wind gaps.

Photographs of present day Snicker's Gap (Virginia Route 7), Ashby Gap (U.S. Routes 17 and 50), and Mannassas Gap (Interstate 66). These gaps were eroded by Beaver Dam Creek, Gap Run, and Goose Creek respectively, prior to the capture and diversion of the headwaters of these streams. (Photographs by Stan Johnson, Base map from The National Map, United States Geological Survey)

• The formation of dry gaps (called "wind gaps") in Virginia's Northern Blue Ridge begins in the geologic past. Below: slide show on the development of the wind gaps.

Slide show

Click to view slides: