The Volcano, also known as Lava Fork volcano, is a small cinder cone in the Boundary Ranges of the Coast Mountains in northwestern British Columbia, Canada. It is located approximately 60 kilometres (40 miles) northwest of the small community of Stewart near the head of Lava Fork. With an elevation of 1,656 metres (5,433 feet) and a topographic prominence of 311 m (1,020 ft), it rises above the surrounding rugged landscape on a remote mountain ridge that represents the northern flank of a glaciated U-shaped valley. Lava Fork volcano is associated with a small group of volcanoes called the Iskut volcanic field. This forms part of the much larger Northern Cordilleran Volcanic Province, which extends from the Alaska–Yukon border to near the port city of Prince Rupert, British Columbia. Eruptive activity at The Volcano is relatively young compared to most other volcanoes in the Northern Cordilleran Volcanic Province. Geologic studies have shown that The Volcano and its eruptive products were emplaced in the last 400 years; this is well after the last glacial period, which ended about 10,000 years ago.
Geology The Volcano is the southernmost of ten volcanoes comprising the Iskut volcanic field, as well as the most recent to erupt. Its structure is poorly formed and has been reduced by erosion from alpine glacial ice found at its elevation and latitude. It represents one of the few historically active volcanoes in the Northern Cordilleran Volcanic Province, with a base elevation estimated to be 100 m (330 ft). Like most cinder cones, The Volcano consists of a pile of loose volcanic ash, lapilli-sized tephra and volcanic bombs. These were deposited during periods of lava fountain activity. The vent area contains volcanic bombs up to 0.5 m (1.6 ft) long and small deposits of sulfur precipitated from volcanic gases. Like other Iskut-Unuk River Cones, The Volcano has its origins in continental rifting—a long rupture in the Earth's crust where the lithosphere is being pulled apart. This incipient rifting has formed as a result of the Pacific Plate sliding northward along the Queen Charlotte Fault, on its way to the Aleutian Trench. As the continental crust stretches, the near surface rocks fracture along steeply dipping cracks parallel to the rift known as faults. Basaltic magma rises along these fractures to create effusive eruptions. The rift zone has existed for at least 14.9 million years, and has created the Northern Cordilleran Volcanic Province. Several dormant volcanoes in the province are potentially active, with The Volcano being one of the three having erupted in the last few hundred years. Tseax Cone, which last erupted in the 18th century, is the southernmost volcano in the province, whereas Prindle Volcano in easternmost-central Alaska, which last erupted more than 10,000 years ago, is generally considered the northernmost.
Volcanic history At least two phases of volcanic activity have been identified at The Volcano. Each event was followed by the eruption of lengthy basaltic lava flows that flowed down steep granitic flanks of the mountain ridge on which The Volcano lies. After this took place, they travelled through the Lava Fork valley for 5 km (3 mi). Here, the flows crossed the British Columbia border into the U.S. state of Alaska and blocked the Blue River, a tributary of the Unuk River, forming several lakes. The lava flows in total are about 22 km (14 mi) long and still contain their original features from when they cooled, including pressure ridges and lava channels. A series of large trees were engulfed by the lava flows during eruption. The bases of the trees burned and the upper trunks and branches collapsed into the solidifying lava, leaving the trees embedded on the surface of the lava flows. After the flows solidified, tree molds and lava tubes collapsed to form volcanic pits. At the southern end of one of the lava flows, it spreads into a broad terminal lobe on the flat alluvial plain of the Unuk River. Volcanic ash and lava from The Volcano still linger on small glaciers near Mount Lewis Cass, a 2,094 m (6,870 ft) high mountain near the Alaska–British Columbia border.
At least one lava flow from The Volcano was notified by a surveyor named Fremont Morse in 1905 during a survey for the International Boundary Commission. In 1906, Morse wrote that the most recently erupted lava flow had "probably occurred within less than fifty years". Since Morse's report, tree ring and radiocarbon dating techniques have been used to establish the dates of The Volcano's two volcanic phases. The first is estimated to have occurred about 360 years ago and the latest possibly took place only 150 years ago. This indicates that The Volcano is the youngest known volcanic mountain in Canada and that its volcanic activity is recent compared to many other volcanoes in British Columbia. In several documents, the last eruption of The Volcano is written to have occurred in 1904. However, according to the Smithsonian Institution's Global Volcanism Program, this eruption is considered uncertain. Although The Volcano is estimated to have last erupted 150 years ago, it is one of the five volcanoes in the Northern Cordilleran Volcanic Province that have recorded seismicity since 1985. Others include Castle Rock (two events), Hoodoo Mountain (eight events), Crow Lagoon (four events) and the Mount Edziza volcanic complex (eight events). Seismic data suggest that these volcanoes still contain active magma chambers, indicating that some Northern Cordilleran volcanoes are probably active, with significant potential hazards. The seismic activity corresponds both with some of Canada's recently formed volcanoes and with persistent volcanoes that have had major explosive activity throughout their history, such as Hoodoo Mountain and the Mount Edziza volcanic complex.
Human history
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