On the Rocks
September 2007

In Search of the Mysteries of Creation
by Leopold Hayden Powell

Land is immortal, for it harbors the mysteries of creation.
In Search of Identity, Anwar al-Sadat, 1978

Come, be a sleuth of natural mysteries along the valleys northeast of Colville. This year's recreational geology trip will travel Mill Creek and Deep Creek to Northport. The tour starts from Park Place Restaurant at 9:30 a.m., Saturday, October 6. Bring your lunch, and curiosity. We will car pool, as much as possible. Professional geologists usually cap a field trip by discussing the issues, with the maps spread out to be annotated with beer and food stains. You can join in, at Northern Ales, with food from the Mustang Grill by making arrangements at hanshan@plix.com, by October 1.

Mill Creek and its north fork, and the two forks of Deep Creek occupy a nearly continuous trough, from near the International Boundary nearly to Colville. Why is this valley and the flanking ridges so long and narrow? They might be more at home in the Appalachian Mountains than the Rockies. Yes, the geology is similar to that of the Blue Ridge and Smokey Mountains. Hmm? The Blue Ridge Mine is near Deep Creek. Old Dominion Mountain overlooks Mill Creek. Miners from the worked out districts of Virginia must have felt at home enough to put the old names on the place. This is part of a curving belt of half billion-year-old sedimentary rocks. The layers have been pushed up as folds miles across and tens of miles long. Cambrian and Ordovician rocks were folded into mountains during Carboniferous time in these Selkirk Mountains, as well as the Appalachians, Atlas of North Africa and Pennines in Britain. Teasing out the differences among all of these mountains provides the clues of unique histories.

Our local rocks and their structure are called the Kootenay Arc, itself an old and out of place name. Canadian mining engineer Matthew Hedley saw the curving pattern centered on Kootenay Lake and so applied the name. That was 1955, shortly before geologists of new disciplines recognized different sorts of arcs, which were to have great significance for the revolutionary theory of plate tectonics. While it is hard to visualize the mile scale pattern, we will put our hands on smaller structures -- tens of feet, feet and inches. Much of the picture is veiled by soil and vegetation. Sometimes the case must be made from disparate clues. We measure and map the orientation of the layers to make sense of the whole picture. The pattern is not perfect to the theory. The valley sidesteps, going from Mill Creek to Deep Creek. The angles of force and resistance were neither perfect nor constant. Later events also changed the scene. We will look at the igneous rocks, which were part of a thermal event one hundred million years ago. Faulting scrambled some of the folds fifty million years ago, but that renewed these mountains, compared to their contemporaries. Oh, yes! There was that four thousand feet thickness of ice, forty thousand years ago.

How do we know these ages? Fossils and their life spans start the deductive process. One species flourishes and becomes extinct. Even before Darwin, collectors recognized that, once a species disappears, it does not reappear. One species survives another, a third survives the second. Two hundred years of careful compilation has built a sequence, from before the Cambrian Period to our time. The animal, which we will see, is an oddity called Archaeocyatha. As one of the first animals with a hard skeleton, it was extremely successful, but only in the Early Cambrian. Geologists have pegged the fossil sequence to years, by measuring radioactive decay. Some elements give up mass and change character by releasing energy, at a constant rate. It's that E=mC2 formula. Sophisticated instruments can measure how many ticks have elapsed since the freezing of a crystal set the clock. We'll drive by a site where such a sample was taken, from the Sprit Pluton. When you are collecting a one hundred kilogram sample, you do not stray far from the road.

After working their way north from California and Nevada, those miners probably welcomed the verdure of Mill Creek. We ask why the Interior Wet Belt starts here? Birch and poplar grow in both regions. Why don't they share a similar profusion of oaks and maples? The answer lies in the glacial history. Northwest Interior soils were ground by glaciers, a few thousand years ago. Forests and floods have built soil, over hundreds of thousands of years, in Appalachian valleys. The gravely, young soils lack the capacity to hold moisture and nutrients, through summer drought. Seasonal scarcity gives advantage to trees that don't have to grow all new leaves, every year.

Every stone and patch of soil and each river bend or wrinkle of the landscape has a story. Join us for a day of Earth literature.

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