The Mount Edziza volcanic shield is a large and potentially active north-south trending shield volcano in Stikine Country, northwestern British Columbia, Canada, located 38 kilometres (24 mi) southeast of the small community of Telegraph Creek. It occupies the southeastern portion of the Tahltan Highland, an upland area of plateau and lower mountain ranges, lying east of the Boundary Ranges and south of the Inklin River, which is the east fork of the Taku River. As a volcanic shield, it consists of many types of volcanoes, including shield volcanoes, calderas, lava domes, stratovolcanoes, and cinder cones.
Most of the Mount Edziza volcanic shield is encompassed within a large provincial park called Mount Edziza Provincial Park. Named after Mount Edziza, this 2,660.95 km2 (1,027.40 sq mi) park was established in 1972 to preserve the volcanic and cultural treasures unique to the northern British Columbia area. The Mount Edziza volcanic complex is remote, and, without roads, accessible only along trails. The easiest access is from Highway 37 and a spur road from Dease Lake to Telegraph Creek. From Kinaskan Lake, on Highway 37, a poorly maintained Trail extends west for 30 kilometres (19 mi) into the heart of the complex. From Telegraph Creek another trail extends east for 25 kilometres (16 mi) to the north slope of Mount Edziza.
The Mount Edziza volcanic shield began forming about 7.5 million years ago and has grown steadily since then. Like other volcanoes in northwestern British Columbia, the Mount Edziza volcanic complex has its origins in continental rifting—a long divergent plate boundary where the lithosphere is being pulled apart. Here, the continental crust of the North American Plate is being stretched at a rate of about 2 cm (1 in) per year.
This incipient rifting has formed as a result of the Pacific Plate sliding northward along the Queen Charlotte
Fault, on its way to the Aleutian Trench, which extends along the southern coastline of Alaska and the adjacent waters of northeastern Siberia off the coast of Kamchatka Peninsula. As the continental crust stretches, the near-surface rocks fracture along steeply dipping cracks parallel to the rift known as faults. Hot basaltic magma rises along these fractures to create passive lava eruptions, known as effusive eruptions.
The Mount Edziza volcanic shield is Canada's second largest volcano of young volcanic activity, with an area of 1,000 km2 (390 sq mi), exceeded only by the Level Mountain Range
north of Edziza, which has an area of 1,800 km2 (690 sq mi). Four central volcanoes, known as Armadillo Peak, Spectrum Range
, Ice Peak
, and Mount Edziza, lie along the northerly trending axis of an oval, composite shield volcano. The composite shield volcano consists of overlapping shields, two of which are clearly noticeable on maps. The composite shield volcano forms a broad lava plateau, 65 kilometres (40 mi) long and 20 kilometres (12 mi) wide, mainly made of basaltic lava flows; it is dotted with cinder cones and surrounded by steep ridges called escarpments, which expose layers of black columnar basaltic lava flows with distal rock fragments and pyroclastic deposits.
Current Activity :
The Mount Edziza volcanic shield is one of the eleven Canadian volcanoes associated with recent seismic activity: the others are Castle Rock, Mount Garibaldi
, Mount Cayley, Hoodoo Mountain
, The Volcano
, Crow Lagoon
, Silverthrone Caldera
, Mount Meager
and Nazko Cone
. Seismic data suggests that these volcanoes still contain live magma plumbing systems, indicating possible future eruptive activity. Although the available data does not allow a clear conclusion, these observations are further indications that some of Canada's volcanoes are potentially active, and that their associated hazards may be significant. The seismic activity correlates both with some of Canada's most youthful volcanoes, and with long-lived volcanic centres with a history of significant explosive behavior, such as the Mount Edziza volcanic shield.
The most recent volcanic activity at the Mount Edziza volcanic shield have been hot springs, several of which are found on the volcano's western flank, including Elwyn springs (36°C or 97°F), Taweh springs (46°C or 115°F), and inactive springs near Mess Lake. The springs are near the youngest lava fields of the Mount Edziza volcanic shield and are most likely associated with the most recent eruptive activity. These hot springs were highly important to the adjacent Tahltan people.
Hot springs are closely associated with fumaroles, which are vents in an active volcanic area releasing steam and hot gases, such as sulfur dioxide. In general, the water is rotating groundwater that comes into contact with rocks heated by magma and finds openings to the surface. The formation of the springs depends both on the rocks the water has passed through and the profusion of volcanic discharges mixed with the groundwater. Iron oxide, iron sulfides and other substances usually colour pools of boiling mud brilliant yellow, red, brown or green. Hot springs comprising significantly softened silica may deposit it to form siliceous sinter, whereas those comprising softened calcium carbonate deposit spongy-looking calcareous rock called tufa. Overflow of the springs can build masses, spires or stepped terraces of sinter or tufa.
Eruptive History :
The lava domes, calderas, stratovolcanoes, subglacial mounds and cinder cones forming the volcanic shield were constructed in five phases, each of which began with the effusion of dark olivine basalt which formed the flat-lying shield volcanoes and concluded with the eruption of light-coloured magma. This cyclical behavior is attributed to the episodic rise of basic, mantle-derived alkali basalt both to the surface and partly into crustal reservoirs where the light-coloured magmas with very little aluminum were created by prolonged crystal fractionation. The silica-rich trachyte and comendite lavas are similar to those associated with the most violent eruptions on Earth.
- Armadillo Peak eruptive period.
- Spectrum Range eruptive period.
- Ice Peak eruptive period.
- Mount Edziza eruptive period.
- Central volcano flank eruptive period.
Elevation : 2,787 m (9,144 ft)
Prominence : 1,750 m (5,741 ft)