| The Barrier | |
|---|---|
 The rock fall area and the edge of The Barrier | |
| Official name | The Barrier |
| Location | British Columbia,Canada |
| Coordinates | 49°56′06″N123°04′48″W / 49.9349°N 123.0800°W /49.9349; -123.0800 |
| Dam and spillways | |
| Type of dam | Lava dam |
| Impounds | Rubble Creek |
| Height | 243 m (800 ft) |
| Length | 2.4 km (1.5 mi) |
| Spillways | 1 |
| Spillway type | Uncontrolled |
| Reservoir | |
| Creates | Garibaldi Lake |
| Surface area | 9.94 km2 (3.84 sq mi) |
| Maximum water depth | 258.7 m (849 ft) |
| Normal elevation | 1,484 m (4,869 ft) |
The Barrier is alava dam retaining theGaribaldi Lake system in southwesternBritish Columbia,Canada. It is over300 m (980 ft) thick and about2.4 km (1.5 mi) long where it impounds the lake.[1]
The area below and adjacent to The Barrier is considered hazardous due to the unstable lava formation.[2]
The Barrier was formed about 15,000–12,000 years ago when large lava flows emanated fromClinker Peak on the west shoulder ofMount Price.[3][4] The large lava flowed towards theCheakamus River valley. At the time of eruption, the valley was probably filled by glacial ice. The lava flow was stopped by the ice and ponded, eventually cooling to form anice-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.[3][4][5]
The unstable lava formation of The Barrier has in the past unleashed severaldebris flows in the area below Garibaldi Lake.[2] The most recent major landslide in 1855-1856 formed a large boulder field that givesRubble Creek its name.[6] At least 30,000,000 m3 (1.1×109 cu ft) of rock was removed from The Barrier during the 1855-1856 event.[7]
Concerns about The Barrier's instability due to volcanic, tectonic, or heavy rainfall activity prompted the provincialgovernment to declare the area immediately below it unsafe for human habitation in 1981.[8] This led to the evacuation of the small resort village ofGaribaldi nearby, and the relocation of residents to new recreational subdivisions away from the hazard zone.[9][10] Should The Barrier completely collapse,Garibaldi Lake would be entirely released and downstream damage in theCheakamus andSquamish Rivers would be considerable, including major damage to the town ofSquamish[11] and possibly an impact-wave on the waters ofHowe Sound that would reachVancouver Island.
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