JARS v61n3 - Two Summers in the Canadian Rockies

Two Summers in the Canadian Rockies
Peter Kendall
Portland, Oregon

The stretch of the Rocky Mountains (from west and slightly south of the resort town of Canmore) in Assiniboine Provincial Park to the northern reaches of Yoho National Park in the province of British Columbia yields so much in the way of geological and horticultural intrigue. The geological spectacle of the Canadian Rockies takes away one’s breath. It invites the question: from when, where and how did such magnificence come to be? To ever so briefly respond to the query, I offer the following sketch.

Some 180 million years ago, with the break up of Pangea, the North American Plate consisted of the granitic Canadian Shield in the east and a rather rolling, non-descript western rampart ending where the Rockies’ main range is today. To the west lay the Pacific Oceanic Plate with its far-flung terranes (major island land masses) moving inexorably east and eventually into and under the North American Plate. This occurred between 120-60 million years ago during the Cretaceous Period and represents the orogeny (mountain building) of the Canadian Rockies we see today.

It was only relatively recently (from some 2 million years to 10,000 years ago) during the ice ages of the Pleistocene that the present-day sculpture emerged. The 700 million-year-old rock or substrate that was uplifted was primarily sedimentary and came from ocean sediments to the west, chiefly organic carbonate (calcium and magnesium carbonate from precipitating marine organisms) and from clastic, nonorganic sediments (colloidal clay particles to large rocks) to the east. Two parallel ranges were thrust upward to heights approaching 10,000 to 12,000 feet. To the east, we see the slip faulting of the Front Range; to the west we observe the block faulting of the Main Range. Over the years, with the breakdown and deposition of materials into rudimentary soil and the ensuing climatic shifts, we find the wealth of plant material extant today.

With forests of spruce, fir and larch, with many species of willow and similar deciduous and evergreen colonizing species (think ericaceous - including rhododendrons probably 40-50 million years ago - among them), many niches for plant material were created. From high alpine reaches to lower meadow environments, the disparate flora is astounding. Accompanying this article are photographs of some of the more spectacular geological sites and remarkable flora from locations I visited.

Peter Kendall is a frequent contributor to the Journal and a member of the Portland Chapter.