エジザ火山群

The composite felsic stratovolcano Mount Edziza and associated satellitic lava domes and pyroclastic cones were constructed over the past 7.5 million years during five magmatic cycles beginning with eruption of alkali basalts and ending with felsic and basaltic eruptions as late about 1,000 years ago. The 7.5 million-year-old (Ma) Armadillo Peak stratovolcano at the south end of the complex is overlapped by the Ice Peak central volcano, which was formed during the early Pleistocene, and contains a caldera largely destroyed by glaciers. The Mount Edziza stratovolcano on the north was formed about 1.0-0.9 Ma. A 2-km-wide, ice-filled caldera truncates its summit; lava domes were subsequently emplaced around its periphery and lava lakes ponded within the caldera and overflowed its rim. Numerous ice-contact features and products of subglacial eruptions are found in the Mount Edziza complex. More than 30 Holocene pyroclastic cones, primarily of basaltic composition, are located on Mount Edziza and the adjacent Spectrum Range, some of which are younger than about 1,300 years before present. Large areas of Holocene lava flows of the postglacial Big Raven Formation are located north of Mount Edziza, forming the Desolation Lava Field, and south and SW of Ice Peak, forming the Snowshoe Lava Field.