Barrier, The

“View of The Barrier” | photo: John Harvey

Barrier, The | geology | The ancient lava dam that helped form and continues to retain Garibali Lake, which is located between the communities of Squamish and Whistler. It was formed at the end of the last Ice Age and is up to 1,000 feet thick in places and approximately 2.5 kilometres wide. Forty years ago, the stability of “The Barrier” was deemed so uncertain and precarious that the government forbade any construction directly beneath it. If it gave way and collapsed (eg. in the entirely possible event of a major earthquake), it would drain Garibaldi Lake as if from a spout, the violent flow of which would devastate everything in its path down to the waters of Howe Sound, including the Sea-to-Sky Highway 99.

Usage: “When I’m camping near Squamish and I feel the distant rumble of a train, I worry for a moment that it might be The Barrier collapsing…”

There are 2 comments

  1. Always good to see posts on geology and disasters! The more imminent threat from the Barrier is a little different though… The catastrophic drainage of Garibaldi Lake is often talked about because it is a visually dramatic hazard. However, the likelihood of it happening any time soon is extremely low. The lake is 1.5 km back from the slowly eroding Barrier so it would require a very unusual structural weakness to provide risk on human time-scales (there is research being done to look into that). That doesn’t mean the Barrier isn’t a problem though! It is actually the smaller, but much more frequent, landslide/flood hazards that affect zoning down the corridor including downtown Squamish. Many major landslides have roared down from the Barrier and temporarily dammed the Cheakamus River – most followed by an outburst flood that flushes down the river through Squamish. The last big landslide event was in 1855. The same type of events have occurred many times from Mt. Cayley temporarily blocking the Squamish River. At least there would be lots of warning before these downstream flood events because it would take time for the Cheakamus or Squamish Rivers to dam up behind a landslide dam. Perhaps they aren’t quite as dramatic as Garibaldi Lake draining… but they could still be pretty crazy – and we are much more likely to see one of these occur!

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