Blue Mountains may extend to Idaho

A story in the July 9, 1987 East Oregonian speculated that the Blue Mountains of Eastern Oregon, commonly thought to extend from Dayton, Washington, to John Day, Oregon, may actually extend as far east as Idaho and include some of the state’s most iconic peaks.

The gentle slopes of the Blue Mountains are in stark contrast to the rugged peaks of the Wallowas and Elkhorns in the northeast corner of Oregon. But most geologists and science writers would include the Elkhorns near Baker, the Strawberries near John Day, the Wallowas and even the Seven Devils range in western Idaho as part of the Blues. And it all has to do with plate techtonics, the motion of land masses that move across the globe on a sea of molten lava far beneath the crust.

According to the theory, one of those pieces of the floating shell, the North American plate, has been colliding with and, in places, overriding the heavier Pacific plate for millions of years. The movements of the plates in relation to each other has, in the case of the Elkhorns and Wallowas, created massive mountain ranges where the North American plate has scraped up features from the Pacific plate, a process called accretion. Studies indicate that the Wallowas were at one time volcanic islands in the Pacific Ocean near the equator. Geologists think that the Elkhorns, including the Anthony Lakes area, were pieces of the ocean floor. And as more pieces of the Pacific plate stack up on the North American plate the coastline — once found in western Idaho, then central Oregon — continues to move westward.

The Blues have a more complicated history. As the Pacific plate is driven (subducted) under the North American plate it melts, re-emerging as lava through thousands of fissures and volcanoes. The Columbia River Basalts, lava flows that covered more than 15,000 square miles in only a week, at depths of up to two miles, occurred sometime between six and 16 million years ago. And for reasons as yet unknown to scientists, the basalts folded in places and formed the hills and valleys familiar to Eastern Oregon residents.

Stan Prowant, a geology professor at Blue Mountain Community College in Pendleton in 1987, suggested that the Blue Mountains actually should be called the “Blue Holes.” Familiar features such as the Blue Mountain Anticline, which extends from central Oregon to the Meacham area, and the smaller Rieth Anticline just west of Pendleton, are examples of the upward folds caused by this geologic action. And Pendleton and Pilot Rock lie along the Agency Syncline, a downward fold in the basalts.

And geologic activity continues in the Blues. Earthquakes shake the area an average of every 15 years, some registering 5 or higher on the Richter scale. And geologist Mark Ferns of the Oregon Department of Geology and Mineral Resources in Baker suggested in the story that future lava flows would not be out of the question. “Troy would be a good place,” Ferns said. “That’s where the most recent flows originated.”