Natural Hazards and Disasters: Volcano of the Week!

Monday, 24 February 2014

Volcano of the Week!

24/02/2014-02/03/2014

This week’s volcano of the week is:

Edziza

Location: NW British Columbia, Canada

Type: Stratovolcano

Elevation: 2786 m, 9138 feet

Last Eruption: 950 CE

Status: Dormant

Details:

Mount Edziza, Canada’s second largest volcano is a composite stravolcano which formed nearly 1 million years ago. The volcano is located in the remote 270,000 hectares Mount Edziza Provincial Park which was established to protect and preserve the volcanic landscape. Continental rifting is responsible for the formation of the volcanic features in this region, of which some date back to over 7.5 million years ago. Ediziza has a 2 km wide summit caldera which is ice-filled and is surrounded by lava domes, more than 30 Holocene, basalitc pyroclastic cones, lava flows and other three other stratovolcanoes called Armadillo Peak, Spectrum Range and Ice Peak.

The pyroclastic cones are estimated to have been formed 1300 years ago from eruptions that took place after Mount Edziza became dormant. One such cone called Eve Cone (shown in the photo) is a symmetrical cone covered with yellow pumice with a height of 150 metres. The volcano is also surrounded by features that provide evidence of sub-glacial eruptions which took place.

The table below from Global Volcanism Program shows the eruption history of the volcano.

Start Date	Stop Date	Eruption Certainty	VEI	Evidence	Activity Area or Unit
0950 ± 1000 years	Unknown	Confirmed	3	Fission track	SW flank of Ice Peak
0610 ± 150 years	Unknown	Confirmed		Radiocarbon (uncorrected)	NNE flank (Williams Cone)
0750 BCE ± 100 years	Unknown	Confirmed		Tephrochronology
6520 BCE ± 200 years	Unknown	Confirmed		Radiocarbon (uncorrected)	North flank?

The formation of the Mount Edziza and the surrounding complex including lava domes, pyroclastic cones, stratovolcanoes and sub-glacier features, were formed by 5 magmatic cycles which began with alkali basalts being erupted and ended with felsic and basaltic eruptions.

Stage 1 involved the creation of Armadillo Peak 7.5 million years ago. This stratovolcano has a small eroded caldera, lava domes, lava flows, pyroclastic density currents and pumice deposits.

Stage 2 resulted in the formation of Spectrum Range 3 million years ago. Rhyolitic magma 150 metres thick and 13 metres long and more than 100 cubic kilometres of rhyolite and trachyte erupted during this phase of Spectrum Range’s activity which ended around 2.5 million years ago.

Stage 3 involved the formation of Ice Peak 1.6 million years ago when glaciers began to retreat. Melting glaciers combined with pyroclastic density currents and lava flows resulting in debris flows. The activity ended 1.5 million years ago with the formation of three lava domes on the western flank of the volcano.

Stage 4 resulted in the formation of Mount Edziza 1 million years ago.

Stage 5 involved eruptions from secondary vents on the volcanoes 10,000 years ago. The 30 cinder cones were formed during this stage.