Earth Sciences Sector > Priorities > Canadian Hazard Information Service > Earthquakes Canada

	Nazko Cone

On Tuesday October 9, 2007, a swarm of small earthquakes commenced in the upper Baezaeko River region, about 100 km west of Quesnel, British Columbia, and was recorded by local seismic monitoring equipment. Eight microearthquakes of magnitude 2-3 occurred on October 10, and more than 100 tremors of less than magnitude 2 have occurred since that date. None of these quakes have been felt by people. Analysis of these seismic data indicated that the earthquakes were occurring about 20 km west of Nazko Cone, at approximately 25 km beneath the earth’s surface.

In order to more easily pinpoint the location and depth of future tremors, Natural Resources Canada personnel installed additional seismic stations in the area. An infrasound station is also being installed; they will record low frequency sound waves below the threshold of human hearing. Natural Resources Canada personnel have also made two visits to the Nazko area in order to update local communities about the situation, collect samples, and examine some of the less well-studied volcanic deposits. They also measured carbon dioxide levels. Carbon dioxide is commonly released along faults and fractures in volcanically active regions and may accumulate in soil or beneath snow, so elevated levels provide information about subsurface magmatic activity. However, all gas measurements in the Nazko region have been within the normal range, indicating no volcanic release of carbon dioxide.

Analysis of the seismic data suggests that magma (liquid rock) is intruding deep within the earth’s crust in the general region of Nazko cone, and is the likely cause of the seismic activity. Based on the number and size of the seismic events, there is no evidence at this time to suggest that a volcanic eruption is likely. It is possible that magma intruding at depth may stall without immediately rising towards the earth’s surface, and swarms of small magmatic earthquakes may occur at volcanoes without being followed by eruptive activity. For example, in 2003, a swarm of deep (29-33 km) earthquakes was recorded beneath Lake Tahoe and attributed to magma, and a vigorous swarm of shallow earthquakes occurred in the area of the Jordan Craters volcanic field of Oregon in 2004.

If magma were to ascend towards the surface in the Nazko region, it is anticipated that the size and number of earthquakes would increase significantly, providing a warning in the very unlikely event of an eruption. If an eruption were to occur, it is our expectation that it would be a small cinder cone building event, similar to the Nazko eruption that took place about 7000 years ago (see below).

Nazko cone is a small, tree-covered volcano in central British Columbia, approximately 75 km west of Quesnel. It is believed to be the easternmost expression of the Anahim hot spot that stretches across central British Columbia from Nazko to the Pacific Ocean. The volcano comprises lava flows, a composite cinder cone, and air-fall tephra. The sequence of eruption at Nazko started with the eruption of two distinct series of fluid lava flows, an older, grey basalt overlain by a younger, darker black basalt. The passive lava eruptions were followed by a period of explosive, pyroclastic eruptions of volcanic bombs and ash. This explosive activity built three overlapping cinder cones that were breached by the eruption of two lava flows near the end stages of the explosive eruptions. Finally, explosive volcanic activity scattered tephra to the north and east of the cones. The tephra deposits are deepest near the cones (>3 m) and thin to less than a few centimetres only a few kilometres away, suggesting that the explosive eruptions were relatively small. However, scientists at the Geological Survey of Canada surmise that this last eruption at Nazko cone may have started forest fires because charcoal is found within the tephra layer.

The lowermost (hence oldest) lava flows at Nazko volcano have been dated at approximately 340 000 years using the K-Ar method. The youngest deposits of air-fall tephra were dated indirectly by analyzing peat above and below the tephra in a bog, and directly by analyzing burned wood within the tephra; the tephra is approximately 7000 years old. The ages for the tephra can be confirmed geologically because the air-fall material is found on top of glacial till deposited during the Fraser Glaciation, which ended about 10 000 years ago. The cinder cones at Nazko are currently mined for their valuable resources of scoria, which is used for light-weight aggregate, landscaping and groundcover, and in agricultural and horticultural applications as a soil additive (Figure A14).

The most immediate hazard relating to future eruptions from Nazko cone is of local concern only and includes the possibility of forest fires and the disruption of local air traffic should an ash cloud be produced.

Figure A14. Nazko Cone Nazko cone is easily reached by road by travelling west from the main highway running through the town of Quesnel, British Columbia. The fire-fountaining eruptions that built the cone produced thick accumulations of scoriaceous tephra, which covered the surrounding landscape. The accumulations of tephra from Nazko cone are over several metres thick in some places. The material is unweathered and unconsolidated, making it a prime target for commercial exploitation. (Photograph by C.J. Hickson (Geological Survey of Canada)) larger image [JPEG, 28.1 kb, 400 X 266, notice]

The lowermost (hence oldest) lava flows at Nazko volcano have been dated at approximately 340 000 years using the K-Ar method. The youngest deposits of air-fall tephra were dated indirectly by analyzing peat above and below the tephra in a bog, and directly by analyzing burned wood within the tephra; the tephra is approximately 7000 years old. The ages for the tephra can be confirmed geologically because the air-fall material is found on top of glacial till deposited during the Fraser Glaciation, which ended about 10 000 years ago. The cinder cones at Nazko are currently mined for their valuable resources of scoria, which is used for light-weight aggregate, landscaping and groundcover, and in agricultural and horticultural applications as a soil additive (Figure A14).

The most immediate hazard relating to future eruptions from Nazko cone is of local concern only and includes the possibility of forest fires and the disruption of local air traffic should an ash cloud be produced.

Nazko cone (Photograph by M.C. Kelman, Geological Survey of Canada)

Nazko cone (Photograph by M.C. Kelman, Geological Survey of Canada)

Geologists measuring carbon dioxide levels near Nazko cone. (Photograph by C.J. Hickson, Geological Survey of Canada)

Seismic station near Nazko cone (Photo by Issam Al-Khoubbi, Natural Resources Canada)

Lava flow at Nazko cone (Photo by C.J. Hickson, Geological Survey of Canada)

Nazko cone tephra (Photograph by C.J. Hickson, Geological Survey of Canada)

Cinder cone eruption