Tuesday, December 04, 2007

Allegheny Plateau Versus Ridge and Valley Regions

I've been working my way through Soil Survey of Pocahontas County, West Virginia, a 300 page pdf file from the Soil Data Mart, a service of the USDA's Natural Resources Conservation Service. I've found this section, Physiography, Relief, and Drainage the most informative source yet on what biogeographical region Droop Mountain falls in.

Pocahontas County lies in both the Eastern Allegheny Plateau and Mountains and the Southern Appalachian Ridges and Valleys Major Land Resource Areas. The dividing line between these areas roughly follows the west side of the Greenbrier River.

The landforms of the county show the effects of orogenic movement coupled with erosional forces. Elevation, kind and position of rock, position of drainage courses, and climate are factors that also affect the type of topography in the county. The plateau and mountain area has nearly horizontal rocks that contain many resistant layers at the higher elevations with more weatherable rock below. This results in a dendritic drainage pattern. The ridge and valley area is slightly to strongly folded with resistant layers separated by large expanses of more weatherable rock. This results in a trellis drainage pattern.

The western part of the county, or plateau and mountain area, is generally higher in elevation and lower in temperature and has a greater amount of precipitation than that of the eastern part of the county, or ridge and valley area. As a result of these factors, a rugged and complicated relief exists. The highest and lowest elevations in the survey area are 4,842 feet at Bald Knob on Back Allegheny Mountain and 1,952 feet where the Greenbrier River flows out of the county.


Rebecca said...

I've always wondered about the exact path of the Allegheny Front through Pocahontas County. Maps do not agree. If it's a line, I'd say it's just East of the river (where the rocks start to tilt). But really I think the whole "Yew Mountain" range IS the Allegheny front... neither Ridge & Valley nor Plateau.


I thought I knew a lot about the mountains of Pocahontas County, but somehow I have missed (or possibly forgotten) that there are two major range distinctions--the Allegheny Mountains on the east and the Ridge and Valley line on the west.
Living in Green Bank for a while, I always marveled at how I could stand by the NRAO runway looking at Back Allegheny Mountain and Bald Knob then turn 180 degrees to see my favorite mountain Ramshorn. Subconsciously, I thought I was seeing the Allegheny Mountains both ways, but a recent view of a map of ranges has my head spinning a little. It's not an impossible concept but a new one.