The Curious Clay Beds of Kwilákm
Kwilákm has an unusual geology. A thick bed of clay, found only in a few other places on Bowen Island and around Howe Sound, underlies the Kwilákm and Snug Cove area. The clay bed has had a profound influence on the shape of the bay and European settlement of Bowen Island.
Clay is geological material made up of very fine mineral grains. This clay bed was formed on an ancient seafloor during the Ice Age from glacial flour carried to the sea by glacial meltwaters. The soft clay banks have been easily eroded by storm waves, causing retreat of clay banks and creating the broad tidal flats of Kwilákm near the Causeway. The gently sloping surface of the clay bed made it an ideal site for the Union Steamship Hotel, Snug Cove village, and later on, the Kwilákm and Snug Point neighbourhoods.
The clay bed was even mined for brick making in the 1800s (see the Deep Bay Brickyards story), fuelling Bowen’s early economy.
The clay bed contains scattered pebbles and boulders, and so along the intertidal shoreline of Kwilákm where the clay is exposed, these stones litter the clay surface. As the ocean waves have eroded the soft clay, these hard stones are left behind. These stones cover the surface so completely in places that they disguise the clay bed beneath. Whenever you see cobbles and boulders in the intertidal zone near the Causeway, you can guess that they are likely eroded from the clay bed.
The strange Ice Age origin of the Clay Bed
The clay bed formed near the end of the Ice Age when sea level was 150 m higher than it is today and the lower elevations of Bowen Island and all of the Vancouver region were seafloor. At that time (13,000 years ago) Ice Age glaciers were melting back up Howe Sound, releasing a great flow of melt waters into the Sound, and icebergs were breaking apart from the glacier front. The melt waters carried huge volumes of glacial flour, rock ground to fine silt by the eroding action of the moving glacier. This glacial flour mud settled out on the sea floor of Howe Sound, creating a thick layer of mud. Pebbles and boulders eroded and carried by the glacier became a part of icebergs that broke free from the glacier front and floated down Howe Sound. As the icebergs melted, these pebbles, and boulders were released, falling down into the muddy seafloor, forming a mix of mud, pebble, and boulder. If you take a close look at the clay bed, you can see all three of these components.