Volcanoes appear to be very much a part of the geology of the brigade trails that run through the Okanagan valley, and I was really interested to hear about the so-called Penticton Chain of Volcanoes, which consists of fourteen or sixteen extinct volcanoes that run in a line, from the city of Penticton, on the south end of Okanagan Lake, up the west shore of the lake as far as Peachland. In exploring this interesting subject, however, I learned that there was more than one chain of volcanoes in this region: there is, I believe, a Kamloopian Chain of volcanoes as well. There are also volcanoes around Kelowna, well outside the supposed range of the so-called Penticton Chain of Volcanoes. In fact, volcanoes are everywhere! One volcano is even to be found in the Similkameen valley, and is called Stemwinder Mountain. Volcanoes come in “belts,” and Stemwinder Mountain is part of the Princeton/Aspen Grove/Nicola Volcanic Belt of South Central British Columbia. If you remember, I identified the base of Stemwinder Mountain as likely being one of the camps that the Fort Colvile brigades used on a regular basis, on their way to and from Fort Langley. https://nancymargueriteanderson.com/similkameen-brigade-trail/
The Okanagan valley was formed some 60 million years ago, when the land was compressed by volcanic islands pressing in from the Pacific Ocean. The force was so intense that it created the mountain ranges that exist today in British Columbia. Then, some fifty-five million years ago, the compression gradually slowed, and stopped, and the land relaxed once more. This compression and relaxation created giant faults (such as the Rocky Mountain Trench), and the entire Okanagan Valley became an enormous fault in the earth’s surface that set up the valley for the volcanoes that followed.
In Squally Point, directly across Okanagan Lake from the town of Peachland, you can see one of the two land surfaces that collided some sixty million years ago. Squally Point is part of the Shuswap metamorphic complex, and a fragment of the Canadian Shield: that is, the western edge of the ancient North American continent. “The Shuswap metamorphic complex is the largest metamorphic core complex in North America,” say the three authors [Sarah R. Brown, Graham D.M. Andrews, and H. Daniel Gibson, quoting P.J. Coney, 1980] of “Corrugated architecture of the Okanagan Valley shear zone and the Shuswap metamorphic complex, Canadian Cordillera.” Truthfully, I don’t understand anything else they say in their article (not being a geologist), but that seems important. The exposed rock at Squally Point is dated at 2.1 billion years of age, and is the oldest rock in British Columbia. But people who live on Okanagan Lake itself are probably more familiar with the deep waters that surround Squally Point, providing excellent diving — as well as the imagined “fact” that Ogopogo lives in a cave somewhere deep under the base of Squally Point.
But that’s not a volcano, and I said I was going to talk about volcanoes. Those volcanoes began erupting across the Okanagan Valley some 40 million years ago! How long they gushed, I do not know, but they are now all quiet. Behind Kelowna stands at least three extinct volcanoes which may or may not be a part of the Penticton Chain of Volcanoes: they are now known as Layer Cake Mountain, Knox Mountain, and Dilworth Mountain. Only Dilworth Mountain made it into my ancient Gazeteer of British Columbia, where it is said to be east of Kelowna. Across the lake from Kelowna, however, and close to the west end of the bridge that crosses the lake, is another extinct volcano: Mount Boucherie, located in modern-day West Kelowna. Although it only rises 2,400 feet above the level of the lake, it is believed to have once had an elevation of 6,500 feet or more.
Lambly Creek was once the scene of volcanic activity as well, and its activity is quite young in comparison to the older mountains. Lambly Creek is just north of Mount Boucherie, and is what the HBC men called Bear Creek. I suppose that its lava could have formed the nearby “Mauvais Rocher” that the HBC men worried about.
So there are a few volcanoes, but none of them I have so far mentioned are apparent members of the Penticton Chain of Volcanoes, which runs from Peachland to Penticton. So far I can find no volcanoes in Peachland, but they must be there. Summerland has a few: the most obvious, of course, is Giant’s Head Mountain, which can be seen from everywhere in the town. It was formed when an ancient eruption shattered the original volcano, catapulting lava bombs across the landscape (as did Rattlesnake Mountain, as you will see below). As you approach Summerland from the south you can see the giant’s face that the glaciers carved into the mountain. Depending on the source, Giant’s Head is either 2700 feet above Okanagan Lake, or 1,600 feet.
Crater Mountain is also an ancient volcano, and one of 16 volcanoes of the Penticton Chain of Volcanoes. It stands across Trout Creek Canyon from the Summerland Golf Course: that seems easy to find. Conkle Mountain is another Summerland volcano (and there probably are more). It is not mentioned in my British Columbia Gazeteer, but Conkle Lake and Conkle Creek are — in fact, Conkle Creek flows south from Conkle Lake into the Similkameen Valley! I presume, perhaps incorrectly, that Conkle Mountain must be a part of the same ridge of rocky hills that Stemwinder Mountain belongs to! Wherever it stands, it is a Summerland park that cyclists, hikers, and runners enjoy.
And there is another interesting geological feature attached to Summerland — the Summerland cannonballs! Rattlesnake Mountain was another Summerland volcano, and the Summerland cannonballs were round rocks created when lava was expelled from the erupting Rattlesnake Mountain (or from Giant’s Head Mountain, see above). It is believed the lava bombs fell into an adjoining lake, where they quickly cooled and kept their round shape.
Skaha Lake is another volcanic place: The Skaha Formation is the youngest formation in the region, it seems, and its rocks crop out in a small area located a half mile east of White Lake, and about 2 miles southwest of Skaha Lake.
And speaking of White Lake: it is volcano central! White Lake is described as a small, ephemeral body of water located in the east central part of the area near the centre of a dish shaped depression. Slopes rise gently from the shores of the lake to summits which seem to be part of the Thompson Plateau. The White Lake valley has five layers of volcanic rock — the lowest layer being the Springbrook Formation. Then comes the Marron Formation, with its five different layers. From bottom to top these different layers are the (1) the Yellow Lake member; (2) the Kitley Lake member; (3) the Kearns Creek member; (4) the Nimpit Lake member; and finally, (5) the Park Rill member.
Modern day Yellow Lake is east of Keremeos Creek, in the Similkameen Valley. Kitley Lake is west of the south end of Skaha Lake, in the Similkameen District. Today’s Kearns Creek flows into Park Rill, west of Vaseaux Lake, and is part of the Similkameen District. I don’t have a location for Nimpit Lake, but Park Rill is very much a part of the Brigade trail, and flows from Twin Lakes down to the south side of McIntyre Bluff. So, I guess these are all volcanoes whose lava flowed into the White Lake Valley, one after another, creating another layer of volcanic activity in that one place.
Then came the Marama Formation which also flowed into parts of the White Lake Basin, and it lies overtop all of the layers of the Marron Formation. This formation goes into the United States and is part of the San Poil Formation in Washington State, south of Greenwood, B.C. Then came the White Lake Formation, which overlaps the Marron and Marama rocks in the east part of the area.
And I mentioned the Springbrook formation: that is, the very bottom layer in the White Lake Basin. Its rocks are also found on bluffs east of Keremeos Creek, above the highway.
So that is a pretty substantial group of volcanoes in the Penticton Chain of Volcanoes, and I am sure I have missed some of them. I don’t know which of these volcanoes are associated with Penticton, but the Penticton Chain of Volcanoes is connected to the Kettle Valley formation of volcanoes at Greenwood and Grand Forks.
And for anyone who wants to learn more about this: the Okanagan Heritage Museum has a display of how the Okanagan Valley was formed. You will find this museum in Kelowna, and it might be an interesting visit. As I am heading up to the Okanagan Valley shortly, it will be interesting to learn more about the geography of that place.
And why am I heading up to the Okanagan? Well, my book, “The HBC Brigades,” will (with luck) be published in the spring of 2024, and I want to make sure that I have everything right.
A word on the image above: the man who painted this image, and others, belonged to the Native Sons of British Columbia, and his paintings celebrated white man’s history in the territory. I find it amusing that although this white man celebrated the passage of the Brigades through the Okanagan Valley, he did not realize that most of the men who worked in the Brigades were Métis or First Nations.
Please feel free to correct any obvious errors I have, or if you wish to add information in the comments, please do so. Thanks (Ken).
Copyright, Nancy Marguerite Anderson, 2023. All rights reserved.
- Michaud House
- Thomas Lowe, 1844