In addition to erratics, there are other rocks standing out, basalt pillars.
The early evening light casts a warm glow on the basalt pillars of Frenchman Coulee, a popular rock-climbing site, in the Quincy Wildlife Area near Vantage. The unique pillars were formed millions of years ago as lava extruded through the Earth’s crust cooled, and later were further sculpted by massive ancient floods.
The Twin Sisters
http://columbiariverimages.com/Regions/ … sters.html
The question is, why didn’t these get eroded as well? Or at least why didn’t they get toppled over by the flood?