On th Rocks
May 2007

Immense Depths of Time
by Leopold Hayden Powell

Our whole past experience is continually in our consciousness, though most of it is sunk in a great depth of dimness. I think of consciousness as a bottomless lake, whose waters seem transparent, yet into which we can clearly see but a little way.
--Charles Sanders Peirce, 1839-1914

Immense depths of past time lie in waters of the Arrow Lakes. Look down, past drowned towns, past ancient First Nations homes, past great streams of glaciers, past mountains being built in time of dinosaurs. It takes sharp detection to see the traces of animals, which lived in seas of three hundred million years ago (they're in the limey crags, south of Arrow Park) . Choose your mode. There is easy paddling to explore away from roads. Bowman Point and Island Point as well as the spectacular Renata natural bridge are only accessible by boat. Fishing is everywhere. Some of the nearby forestry roads are good mountain bike routes. You can even skindive the drowned town sites of Beaton, Arrowhead, and Comaplix.

We will need to get off of the highways to appreciate this slice into time. With Highways 6 and 23, and Trans-Canada 1 crossing the lakes, the Roadside Geology of Southern British Columbia (Bill Mathews and Jim Monger, Mountain Press) is still a great guide. They pay most attention to bedrock. We can fill in on the most recent parts, glaciation and landscape. The rivers and lakes combine with highways and railroads to place a network across that landscape. Tangential forces built our regions mountains by twisting and tumbling hundred kilometer blocks of lithosphere. Glaciers and rivers carved valleys, looping around the texture of those blocks. People had traveled the Omineca and Selkirk Mountains for millennia by way of the lakes and rivers. Early trail, road and rail builders wove a weft, between river crossings, on the warp of river routes.

The Arrow Lakes are not the lakes they once were. For thousands of years, narrow, curving Lower Arrow was separated by eleven kilometers of swift water from thorn-shaped Upper Arrow. Hugh Keenleyside Dam was closed in 1968, raising the level of the Columbia by forty-two meters. Two lakes became one reservoir 232 kilometers long. Lakes are stable over many generations. The water levels vary over a meter or less. Black cottonwood, whiplash willow, coyote willow and red-twig dogwood grow with their roots washed by the stable water. Beaver, muskrats and otters denned under root shelters. Osprey built nests in inevitably broken tops of cottonwoods. Sockeye and dolly varden found spawning gravel in wave-lapped shallows. Reservoirs' water levels vary by tens of meters during the year. The riparian trees are gone, and with them most of the fur bearers. The sockeye and dolly varden are replaced by kokanee and eastern brook trout spawning in the tributaries. Osprey have adopted the Hydro transmission poles.

A geologist or hydrologist looks at the Lakes and wonders, "How does such a long, flat stretch of river come to be in mountain country?" Well, spar the number crunching of gradient -- the fall divided by stream distance. Here the gradient is very low, by mountain standards. The Columbia, Castlegar to the sea is twice as steep. Skeena from Kispiox to the sea is twenty times steeper. Before the First Nations came, this region was completely covered by ice, at least twice -- maybe four times. The glaciers were not deep, above the peaks, as was the glacier covering of central and eastern Canada. Shallow glaciers are usually "dry based." That is, they are melting a bit, at the bottom, all of the time. Hot springs, at Octopus Creek, Nakusp, St. Leon, Halfway River and Halcyon, must have helped. Most of the glacier flow was along the preexisting valleys, lubricated by high pressure melt water. The combination made an extremely efficient erosion machine. Even as the weight of the ice pressed the Earth's crust down by a hundred meters, the grindings could be transported up from hollows and toward the low pressure to the south.

When the ice front had melted back nearly to Nakusp, a moraine was left at the valley bend near Arrow Park. Gravel terraces on the valley sides record the successive outlets for melt water: first over Summit Lake and down the Slocan, then over Frosthall and down Mosquito Creek and the Whatshan River. Finally the ice plug relented to let water over the moraine to finish carving Lower Arrow Lake.

Don't let hauling in a fish distract you from contemplating the depths of history.

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