The volcanic history of the Northern Cordilleran Volcanic Province presents a record of volcanic activity in northwestern British Columbia, central Yukon and the U.S. state of easternmost Alaska. The volcanic activity lies in the northern part of the Western Cordillera of the Pacific Northwest region of North America. Extensional cracking of the North American Plate in this part of North America has existed for millions of years. Continuation of this continental rifting has fed scores of volcanoes throughout the Northern Cordilleran Volcanic Province over at least the past 20:million years (see Geology of the Pacific Northwest) and occasionally continued into geologically recent times.
Eruptive activity in the Northern Cordilleran Volcanic Province throughout its 20:million year history has been mainly the production of alkaline lavas, including alkaline basalts. A range of alkaline rock types not commonly found in the Western Cordillera are regionally widespread in the Northern Cordilleran Volcanic Province. These include nephelinite, basanite and peralkaline phonolite, trachyte and comendite lavas. The trachyte and comendite lavas are understood to have been created by fractionation of mainly alkali basalt magma in crustal reservoirs. An area of continental rifting, such as the Northern Cordilleran Volcanic Province, would aid the formation of high-level reservoirs of capable size and thermal activity to maintain long-lived fractionation.
In the past 15:million years, at least four large volcanoes have formed their way through dense igneous and metamorphic composed bedrock of this part of North America. This includes Hoodoo Mountain, the Mount Edziza volcanic complex, Level Mountain and Heart Peaks, which are primarily located in northwestern British Columbia. Most notable of these is the 7.5:million year old Mount Edziza volcanic complex, which has had more than 20 eruptions in the past 10,000:years. The only activity present in the Northern Cordilleran Volcanic Province has been occasional earthquakes and constant boiling of hot springs. However, a high potential exists for renewed eruptive activity that could threaten life and property in the volcanic zone.
- 1 Production and rates in volcanism
- 2 Volcanic activity begins
- 3 Volcanism 5.3 to 1.6 million years ago
- 4 Volcanism 1.6 million to 10,000 years ago
- 5 Volcanism in the past 10,000 years
- 5.1 Recent activity and hazards
- 6 See also
- 7 References
Production and rates in volcanism
More than 100:eruptions have occurred in the past 20:million years with a broad range of eruptive styles. These volcanic processes have created a range of different volcanic landforms, including stratovolcanoes, shield volcanoes, lava domes and cinder cones, along with a few isolated examples of rarer volcanic forms such as tuyas. Large persistent volcanoes of the Northern Cordilleran Volcanic Province can remain dormant for hundreds or thousands of years between eruptions and therefore the greatest risk caused by volcanic activity is not always readily apparent. Volcanics older than 14:million years are mainly found in the northern portion of the volcanic province while volcanics ranging from nine to four million years old exist only in the middle of the volcanic province. At least three types of volcanic zones are present in the Northern Cordilleran Volcanic Province, including large persistent lava plateaus like those found at the Mount Edziza volcanic complex, polygenetic volcanoes such as Hoodoo Mountain and monogenetic volcanoes like the basaltic cinder cones found throughout the volcanic province. When Northern Cordilleran volcanoes do erupt, pyroclastic flows, lava flows and landslides can devasta... ...read more