Geology Reference
In-Depth Information
The east-west orientation of the Blue Moun-
tains contrasts sharply with the rest of Oregon's north-
south ranges because they are part of a much larger
structural system that starts in California and trends
northward through the Klamaths to turn sharply
northeast before passing under the Cascades. At the
Snake River, the system swings abruptly northwest to
merge with the Cascades in Washington, where it again
angles northward. Known as an "orocline", this major
S-shaped bend in the older Mesozoic rocks is called the
Columbia Arc.
Extending from north of Powell Buttes in
Crook County almost to Lewiston, Idaho, one of the
most obvious structures in the northern part of the
province is the Blue Mountains anticline, which began
The Wallowa Mountains were carved by 9 major
glaciers during the Pleistocene epoch. Reconstruct-
ed here the glaciers followed a radial pattern out of
the range.
