Geology Tour Part II - Intro
Saturday, August 18
OHA’s 2012 outdoor Highland Wonders season closed with an all day tour, “Geology of the Okanogan Highlands,” led by Steve Box (USGS), Ralph Dawes (WVC), and Cheryl Dawes (B.S. Geological Sciences). Transported by a school bus, community members stopped in several locations along a loop that spanned the Republic and Toroda Grabens as well as the Okanogan Metamorphic Core Complex. From pictographs to garnets, and from volcanic/granitic faults to the highly unusual Corkscrew Mountain, the group considered a diverse array of features that shape the landscape as we know it.
The Geologists leading the event shared insight based on their experience and training. Participants learned about rocks and minerals (how to read them to understand the history and present-day geologic activity of the land), and structural geology (the history of faulting and other deformation preserved in the rocks). “I love learning, teaching, and sharing geological experiences because the planet we live on is, in its own way, a living, breathing entity, with its own distinctive behavior, its own anatomy and physiology,” says Ralph Dawes.
The geology tour explored the effects of a major change in tectonic plate motions that happened within the Pacific Ocean basin about 50 million years ago. “This change led to significant thinning of the continental crust across the Pacific Northwest, and most of the geologic features along the Hwy 20 corridor across the Okanogan Highlands reflect this event,” Stephen Box says. The group also discussed the faults that resulted, as well as the explosive volcanoes that erupted, the metals that were deposited when groundwaters became hot, and the granite that formed from cooled molten rock.
Participants considered how the rocks of the Okanogan Highlands are a combination of ancient North America, exotic terranes brought in by moving plates, and younger volcanic and sedimentary rocks that feature fossils and gold deposits. The tour also discussed the effects of the glaciation of the Highlands, which sculpted the peaks and left boulders from Canada strewn erratically on the landscape.