Hotspot volcanoes

Are there volcanoes near Whistler, BC?

Here in the weekthere Under Museum Musings, we mostly explore and share stories from the past. Rarely, however, do we go back thousands or millions of years as necessary when discussing the geological history of our region. To celebrate the Sea to Sky Fire and Ice Aspiring Geopark, the Museum is showcasing the landscape in the new exhibition Shaping the Landscape with Fire & Ice.

Over time, fire and ice have played an important role in shaping the earth. Whistler is in the converging tectonic plate subduction zone, where the Juan De Fuca Plate is pushed under the North American Plate, creating the Coast Mountains. All of the volcanoes considered active in Canada are found in British Columbia and the Yukon along tectonic plate boundaries, and all are part of the Pacific Ring of Fire.

Garibaldi Provincial Park takes its name from Mount Garibaldi (itself named after an Italian soldier, Giuseppe Garibaldi), the largest mountain in the park and a potentially active stratovolcano. While the last eruption was around 13,000 years ago, it is still relatively recent in geological time (Black Tusk, on the other hand, probably erupted around 170,000 years ago). Volcanoes can erupt again after being dormant for thousands of years. Fortunately, if Mount Garibaldi were to come back to life, we would begin to see warnings such as hot springs, hotspots, and seismic activity in the area due to rising magma.

While Mount Baker is instantly recognizable as a volcano, Mount Garibaldi is harder to tell apart, as it is not a typical cone-shaped volcano. When Mount Garibaldi erupted during the last ice age, half of the volcanic cone formed on a rock foundation, while the western side sat on top of a glacier. As the glacier melted and retreated, the mountain collapsed, changing shape. Giant landslides spread volcanic debris across the Squamish Valley.

We can thank this active volcanic region for the formation of Lake Garibaldi. Also near the end of the last glaciation, Clinker Peak on the shoulder of Mount Price erupted. The Cheakamus Valley was full of rapidly melting ice over 1.3 miles above sea level. Lava from the Clinker Peak eruption flowed to the valley below where it struck the Cheakamus Valley glacier. There it cooled rapidly against the wall of ice, solidifying to create a dam across the mountain valley. As snow and ice melted from the mountains above, they became trapped behind this wall, known as The Barrier, creating Lake Garibaldi.

The only water that leaves Lake Garibaldi all year round springs from the scree slope below The Barrier. This constant flow of water lubricates the naturally unstable dam bottom and poses a significant geological hazard, with some scientists fearing it could one day collapse. It is not uncommon to see rocks falling from The Barrier, hence the name Rubble Creek below, and according to Aboriginal oral histories a major landslide occurred in 1855 when a slab of rock fell from The Barrier. With an estimated 1.28 trillion liters of water trapped by an unstable dam wall 1,400 meters above sea level, a collapse could be catastrophic. It was for this reason that an evacuation order for the townsite of Garibaldi was issued in 1980, with the last residents leaving the town in 1986. Today, the townsite of Garibaldi no longer exists.

Shaping the Landscape with Fire & Ice is now at the Whistler Museum, open from 11 a.m. daily except Wednesday. Admission is by donation and you can further support the Whistler Museum by becoming a member of the museum.