PHOTO PATTERN DATA ELEMENTS: BASALT FLOW
The Columbia Plateau- The Walla Walla Plateau has an extensive field of lava with
young incised valleys in a large basin-like area. Flows of molten rock accumulated in
layers several thousand feet thick. Large streams have dissected the plains into ridges and
valleys. Faulting and fracturing of the lava surface was followed by uplift or tilting of the
resulting blocks to form island ridges. (Semi-arid)
Form
Ridge, interbedded, dissected, terraced hillsides; saw tooth
edges where basalt flow is more resistant.
Drainage
Parallel, dendritic.
Gully Characteristics
Vary from steep V-shaped to box-shaped.
Special Features
Parallel ridges.
Color (Photo Gray Tones)
Light to medium gray.
Land Use
Mostly barren or grass and shrub-covered in rougher
areas, cultivation on terraced hillsides.
Vegetation
Grass and shrub cover, agricultural crops.
Source: Terrain analysis procedural guide for surface configuration, US Army engineer
topographic laboratories, p. 7-109