Geology of Bear Creek Canyon

Dr. Murray A. Roed

There is perhaps no better place in the Okanagan to visualize some of the geologic events that have shaped the land than Bear Creek canyon on the western side of the lake. Most of the major geologic deposits in the canyon can be seen from a high viewpoint on the north side of the valley.

Deposits and Rock Types

Two major types of geologic material occur. One type is unconsolidated…this includes sand and gravel deposited by Bear Creek along its stream bed and in a large fan that juts into Okanagan Lake. Another unconsolidated material consists of glacial deposits that includes sand and gravel formed from melt water as glaciers melted, and glacial till, a mixture of silt, clay, sand and boulders, formed when ice melted.

The other type of geologic material is the bedrock. Bedrock consists of consolidated hard rocks that are of three different kinds….sedimentary, igneous and metamorphic. Most of the sedimentary rocks at Bear Creek are fine grained, gray to black siltstone and sandstone. Igneous rocks include volcanic lava rock, and coarsely crystalline granite. Volcanic rock is molten lava that pour out onto the surface from deep in the Earth. Granite is also from molten material but never reached the surface, and was slowly cooled forming large crystals…thus, granite is an intrusive igneous rock, and volcanic rocks are extrusive igneous rocks.

Origin of Okanagan Lake

Okanagan Lake is a long very deep lake. It was first formed long ago by a very large break in the bedrock called a fault. Ancient rivers began to flow and erode the valley, and large volcanoes, very explosive ones, filled up the valley forming Knox Mountain and Mount Boucherie, for examples. However, the valley was more recently deeply gouged out during several glacial periods of the Ice Age, starting about two million years ago. The glaciers acted like giant plows that carved out even the hardest bedrock along the valley.

At the end of the Ice Age, the valley became dammed near Okanagan Falls and a huge lake formed from all the melting glacier ice. This was Glacial Lake Penticton. All of the orchard terraces, and the distinctive silt bluffs in the Okanagan are formed from deposits in this glacial lake.

Then, the dam suddenly broke and a huge flood eroded the lake basin washing out the main part of the valley. Al the streams entering the valley, including Bear Creek, then began to erode and cut into the sides of the valleys, and this event formed the canyons, waterfalls, and alluvial fans and deltas that we can see today.

North Viewpoint

Beginning at the top of the upland of the canyon the cliffs expose glacial till deposited by the Fraser Glacier over 10,000 years ago. Beneath the till is a valley basalt, often over 100 meters thick, that erupted from a vent far up the valley 176,000 years ago and flowed down the valley all the way to the Valleyview area of west Kelowna. This volcanic deposit is called the Lambly Creek valley lava flow (Bear Creek is also called Lambly Creek).

Below the basalt cliffs and hard to see is a layer of gravel deposited by an ancient Bear Creek; this gravel likely contains the gold that has been found along the present day creek bottom. Dig into the gravel along the creek and try your luck in finding some gold!

Below the basalt and gravel is a thick sequence of folded and faulted rocks belonging to the Nicola Group of rocks of Triassic age. This formation consists mainly of siltstone and sandstone that make up part of the Quesnellia Terrain recognized over a large area of British Columbia. This Terrain is a huge slice of rocks that was thrust over much of British Columbia during the first phases of Continental Accretion during the late Jurassic Period. Geologists refer to this kind of mountain-building as plate tectonics.

The bald rock cliff forming the north side of the canyon is a coarse-grained white and pink granite known as the Coryell Intrusive, representing a late Tertiary igneous intrusion. Pieces of this rock can be seen strewn along the trail on the north side of the canyon.

The Bear Creek falls are spectacular, but like other falls in the Okanagan, they are hard to get to see in totality. They flow through a sinuous, torturous and narrow canyon with an overall vertical drop of at least 100 meters. This viewpoint therefore does not depict the falls to full advantage; another view is available on the south trail of the canyon.

The present day Bear Creek Canyon was eroded initially by huge volumes of glacial melt water from the melting of the Fraser Glacier. This occurred about 10,000 years ago and material was dumped into Glacial Lake Penticton which was about at the level of this viewpoint. As the lake dropped to near its present level, Bear Creek cut deeply into the landscape forming the canyon and waterfalls for which it is so well known, and the creek eventually deposited a low alluvial fan at its mouth. This fan now juts into the lake where the campground of the park is located.

This viewpoint also affords a panorama toward the southeast. If one was as tall as the nearby trees, you would see Little White Mountain in the far distance jutting up from the Hydraulic Lake Plateau. The lowland across the lake is the present site of the City of Kelowna, and the hill to the left is Knox Mountain ending at Poplar Point at the lake edge.

MAP OF BEAR CREEK PARK TRAILS