The Barrier

The Barrier is a lava dam retaining the Garibaldi Lake system in southwestern British Columbia, Canada. It is over 300 m (980 ft) thick and about 2.4 km (1.5 mi) long where it impounds the lake.[1]

The Barrier
The rock fall area and the edge of The Barrier
Official nameThe Barrier
LocationBritish Columbia, Canada
Coordinates49.9349°N 123.0800°W / 49.9349; -123.0800
Dam and spillways
Type of damLava dam
ImpoundsRubble Creek
Height243 m (800 ft)
Length2.4 km (1.5 mi)
Spillways1
Spillway typeUncontrolled
Reservoir
CreatesGaribaldi Lake
Surface area9.94 km2 (3.84 sq mi)
Maximum water depth258.7 m (849 ft)
Normal elevation1,484 m (4,869 ft)

The area below and adjacent to The Barrier is considered hazardous due to the unstable lava formation.

Formation

The Barrier was formed about 9,000 years ago, when large lava flows emanated from Clinker Peak on the west shoulder of Mount Price. The large lava flowed towards the Cheakamus River valley. At the time of eruption, the valley was filled by glacial ice. The lava flow was stopped by the ice and ponded, eventually cooling to form an ice-marginal lava flow. When the ice melted away, the ice-cooled lava-flow front formed a precipitous cliff; water ponded behind the lava dam, forming Garibaldi Lake.

Rubble Creek boulder field

The unstable lava formation of The Barrier has in the past unleashed several debris flows in the area below Garibaldi Lake. The most recent major landslide in 1855-1856 formed a large boulder field which gives Rubble Creek its name.[2] At least 30,000,000 m3 (1.1×109 cu ft) of rock was removed from The Barrier during the 1855-1856 event.[3]

Hazards

Concerns about The Barrier's instability due to volcanic, tectonic, or heavy rainfall activity prompted the provincial government to declare the area immediately below it unsafe for human habitation in 1981.[4] This led to the evacuation of the small resort village of Garibaldi nearby, and the relocation of residents to new recreational subdivisions away from the hazard zone.[5] Should The Barrier completely collapse, Garibaldi Lake would be entirely released and downstream damage in the Cheakamus and Squamish Rivers would be considerable, including major damage to the town of Squamish[6] and possibly an impact-wave on the waters of Howe Sound that would reach Vancouver Island.

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See also

References
  1. BCGNIS Geographical Name Details
  2. Catalogue of Canadian volcanoes - Garibaldi volcanic belt Archived 2009-06-26 at the Wayback Machine Retrieved on 2007-09-07
  3. "Where do landslides occur?". Government of British Columbia. Retrieved 2010-03-03.
  4. Fire and Ice: Distinctive landscape features of Garibaldi Provincial Park
  5. Ferreras, Jesse. "The Barrier remains a concern". Pique.
  6. Powell, Michael. "Garibaldi Lake a ticking time bomb". Squamish Chief.
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