Western Oregon Not Firmly Anchored To North America
Global Positioning System (GPS) units reveal that western Oregon is rotating clockwise relative to the rest of North America. Part of the state is grinding against Washington. But Oregonians will not get dizzy. The periphery moves only a few millimeters each year.
(Anonymous; "In a Spin," New Scientist, p. 25, October 7, 2000. Source cited: Geophysical Research Letters, 27:3117, 2000.)
Comment. Western Oregon is probably a "terrane" -- an exotic chunk of real estate that drifted in from somewhere in the Pacific and lodged up against the North American coastline. Nlany such terranes have piled up against western North America in the geological past.
But what causes the differential rotation?