Mountain Ranges of South Eastern British Columbia and Western Alberta
Most of the parks I visited were in the Canadian Rocky Mountains. However, the first 4 parks I visited (Valhalla Provincial Park, Kokanee Glacier Provincial Park, Mount Revelstoke National Park, and Glacier National Park) were in the Selkirks. One park (Wells Gray Provincial Park) was unusual in that it was associated with volcanic activity.
The Selkirks are part of the Columbia Mountains, and are distinct from, and geologically older than, the Rocky Mountains. The geology of the Selkirks is quite different from the Rockies and from the Purcells and other ranges to the West. Some of the rocks are the oldest outside the Pre-Cambrian shield, dating about 600 million years. Before the Rockies were thrust up by continental drift, the Selkirks stood alone as an island of mountains bordering the Pacific Coast with an inland sea separating them from the Shield. The Columbia Mountains include 4 subranges – the Caribou Mountains, the Monashee Mountains, the Selkirk Mountains, and the Purcell Mountains (Percell in the U.S.)
The Columbia Mountains and the Rockies were built from southwest to northeast, beginning
about 185 million years ago in the western Columbias and ending about 55 million years ago in the eastern foothills of the Rockies. The basement was upthrust extensively in the Columbia Mountains. You see banded black-and-white basement gneiss (pronounced “nice”) along the Trans-Canada Highway around Revelstoke, for example, and along Highway 5 southwest of Valemount. But in the Rockies the basement is exposed at the surface only at a few spots along the Rocky Mountain Trench. In the Columbia Mountains you also find younger gneiss and granite (igneous rock crystallized from deeply buried areas of magma) produced during the plate collision. There is no granite in the Canadian Rockies.
Valhalla Provincial Park
The major group of rocks underlying the Valhallas is known as the Valhalla Gneiss Complex.
The Valhalla Complex consists of a succession of low dipping, gneiss rocks composed of granitic and granodiorite formations of heterogeneous texture and composition which are a part of the Shuswap Metamorphic Complex in southeastern British Columbia. The Nelson Batholith forms the geologic base for the Valhallas. This massive intrusion, upthrust some 20 million years ago, has evolved from rocks in the deep zone of the mountain belt. The batholith originally underlaid sedimentary rocks which were deposited during the Mesozoic era. Throughout the evolution of the Valhalla Complex, there is clear evidence of close inter-dependence of structural evolution, metamorphism, magmatization and granite emplacement.
Wells Gray Provincial Park and a volcanic field
Wells Gray Provincial Park was established to protect Helmcken Falls and the unique features of the Clearwater River drainage basin, including a volcanic field – the Wells Gray-Clearwater volcanic field.
The Wells Gray-Clearwater volcanic field began forming approximately 3,500,000 years ago and has grown steadily since then. Lava flows of 6 cubic miles occurred during the Pleistocene. At the end of the last ice age approximately 10,000 years ago, massive floods from the melting glacial ice carved deep canyons into the underlying plateau-capping lava flows. Most of these canyons contain rivers such as the Murtle and Clearwater, and waterfalls such as Canim Falls, Moul Falls, Spahats Falls and the 463 foot high Helmcken Falls. The faces of the basaltic lava flows and waterfalls remain vertical due to the nature of the basaltic lava flows. Basaltic lava shrinks as it cools and forms vertical columns of rock called columnar basalt. More recently, the southern end of the volcanic field has experienced continuous volcanic activity since the end of the last ice age. The Dragon Cone near Ray Lake has been dated to about 7,600 years old and Kostal Cone near Kostal Lake occurred perhaps as recently as 400 years ago.
The Rocky Mountains
The Rocky Mountains were initially formed from 80 million to 55 million years ago during the Laramide orogeny, in which a number of plates began to slide underneath the North American plate. The angle of subduction was shallow, resulting in a broad belt of mountains running down western North America. Since then, further tectonic activity and erosion by glaciers have sculpted the Rockies into dramatic peaks and valleys.