Northern Cordilleran Volcanic Province

Geologic province in the Pacific Northwest of North America

The Northern Cordilleran Volcanic Province (NCVP), formerly known as the Stikine Volcanic Belt, is a geologic province defined by the occurrence of Miocene to Holocene volcanoes in the Pacific Northwest of North America. This belt of volcanoes extends roughly north northwest from northwestern British Columbia and the Alaska Panhandle through Yukon to the Southeast Fairbanks Census Area of far eastern Alaska, in a corridor hundreds of kilometres wide. It is the most recently defined volcanic province in the Western Cordillera. Apart from the large volcanoes, several smaller volcanoes exist throughout the Northern Cordilleran Volcanic Province, including cinder cones which are widespread throughout the volcanic zone. Most of these small cones have been sites of only one volcanic eruption; this is in contrast to the larger volcanoes throughout the volcanic zone, which have had more than one volcanic eruption throughout their history. The Northern Cordilleran Volcanic Province is part of an area of intensive earthquake and volcanic activity around the Pacific Ocean called the Pacific Ring of Fire. However, the Northern Cordilleran Volcanic Province is commonly interpreted to be part of a gap in the Pacific Ring of Fire between the Cascade Volcanic Arc further south and the Aleutian Arc further north. Nevertheless, the dispersed population within the volcanic zone has witnessed few eruptions due to remoteness and the infrequent volcanic activity.

The Northern Cordilleran Volcanic Province has been a zone of active volcanism since it began to form 20 million years ago. Unlike other parts of the Pacific Ring of Fire, the Northern Cordilleran Volcanic Province has its origins in continental rifting—an area where the Earth's crust and lithosphere is being pulled apart. The continental crust at the Northern Cordilleran Volcanic Province is being stretched at a rate of about per year. This incipient rifting 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 off the southern coast of the Kamchatka Peninsula. As these far field forces stretch the North American crust, the near surface rocks fracture along steeply dipping faults parallel to the rift zone. Hot magma rises between these fractures to create passive or effusive eruptions. Volcanoes within the Northern Cordilleran Volcanic Province are located along short northerly trending segments which in the northern part of the volcanic province are unmistakenably involved with north trending rift structures, including synvolcanic grabens and grabens with one major fault line along only one of the boundaries (half grabens). Alkaline basalt, lesser hawaiite and basanite magmas from effusive eruptions create the massive shield volcanoes and small cinder cones throughout the volcanic province, several of which comprise lherzolite magma. Analysis of recent data related to earthquakes in the southwestern portion of the volcanic province indicates that the crust under Stikinia, which comprises the bedrock underlying a large number of volcanoes in the southern portion of the Northern Cordilleran Volcanic Province, is also more dense than the crust under the nearby Coast Plutonic Complex, which consists of a broad belt of granitic and dioritic intrusive rocks that collectively represent more than 140 million years of nearly continuous subduction related magmatism. With a temperature of , the springs are the hottest in Canada. Sections of these collapsed lava tubes now form volcanic pits. Subvolcanic intrusions in the Northern Cordilleran Volcanic Province are exposed in areas of high relief. The offset caused the Northern Cordilleran Volcanic Province and the terrains of which the volcanic province occupies to move northwards. In the context of plate tectonics, strip slip movement of the Tintina Fault is also related to strike slip movement along the San Andreas Fault and other extensional or strike slip fault systems of western North America. To the west, the Denali Fault is the source of minor earthquakes that extend along the length of the fault. In contrast to the Tintina Fault, strike slip movement along the Denali Fault has offset at least of the surface. The fault separates mountains of the Insular Belt from mountains east of the fault. Tectonic events in the Insular Belt are also related to movement along the Denali Fault.

The term Stikine Volcanic Belt was originally defined by Jack Souther and Christopher Yorath of the Geological Survey of Canada in 1991 as a group of volcanic deposits centered around the Stikine River in northwestern British Columbia. As more mapping and dating of volcanic deposits was completed in the Western Cordillera, the Stikine Volcanic Belt was expanded to include volcanic deposits further and further from the geographic area associated with the name Stikine. In part for this reason, scientists Ben Edwards and James Russell redefined this area of volcanism as the Northern Cordilleran Volcanic Province. As a geographic descriptor, application of the name Stikine to volcanic rocks exposed along the Yukon River seems a bit odd and confusing. As well, a much older group of totally unrelated volcanic rocks comprise the Stikine Assemblage, which also mainly occurs within the geographic area informally referred to as Stikine Country. The Northern Cordilleran Volcanic Province is a broader name, to encompass a broader geographic area, in which the most recent volcanism has a similar character (mainly alkaline, mafic volcanic rocks), a similar age range (Miocene to Holocene), and a similar tectonic setting (transtension).