Rhyolite is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent of granite.
The Chilcotin Group, also called the Chilcotin Plateau Basalts, is a large area of basaltic lava that forms a volcanic plateau running parallel with the Garibaldi Volcanic Belt in south-central British Columbia, Canada.
Satah Mountain is a twin-peaked mountain in the West-Central Interior of British Columbia, Canada. It is southeast of Punkutlaenkut Lake and east of the community of Anahim Lake in Range 3 Coast Land District.
Nazko Cone is a small potentially active basaltic cinder cone in central British Columbia, Canada, located 75 km west of Quesnel and 150 kilometers southwest of Prince George. It is considered the easternmost volcano in the Anahim Volcanic Belt. The small tree-covered cone rises 120 m above the Chilcotin-Nechako Plateau and rests on glacial till. It was formed in three episodes of activity, the first of which took place during the Pleistocene interglacial stage about 340,000 years ago. The second stage produced a large hyaloclastite scoria mound erupted beneath the Cordilleran Ice Sheet during the Pleistocene. Its last eruption produced two small lava flows that traveled 1 km to the west, along with a blanket of volcanic ash that extends several km to the north and east of the cone.
The Itcha Range, also known as the Itchas, is a small isolated mountain range in the West-Central Interior of British Columbia, Canada. It is located 40 km (25 mi) northeast of the community of Anahim Lake. With a maximum elevation of 2,375 m (7,792 ft), it is the lowest of three mountain ranges on the Chilcotin Plateau extending east from the Coast Mountains. Two mountains are named in the Itcha Range; Mount Downton and Itcha Mountain. A large provincial park surrounds the Itcha Range and other features in its vicinity. More than 15 animal species are known to exist in the Itcha Range area, as well as a grassland community that is limited only to this location of British Columbia. The Itcha Range is within territory which has been occupied by aboriginal peoples for millennia. This area has a relatively dry environment compared to the Coast Mountains in the west.
Volcanic activity is a major part of the geology of Canada and is characterized by many types of volcanic landform, including lava flows, volcanic plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes, and maars, along with less common volcanic forms such as tuyas and subglacial mounds.
The Ilgachuz Range is a name given to an extinct shield volcano in British Columbia, Canada. It is not a mountain range in the normal sense, because it was formed as a single volcano that has been eroded for the past 5 million years. It lies on the Chilcotin Plateau, located some 350 kilometres (220 mi) north-northwest of Vancouver and 30 km north of Anahim Lake. The highest peak of the range is Far Mountain. The range supports a unique grassland ecosystem. This type of grassland has not been seen anywhere else in central and southern British Columbia. The climate is cool and dry; typical of higher elevations of the Interior Plateau.
The Anahim hotspot is a hypothesized hotspot in the Central Interior of British Columbia, Canada. It has been proposed as the candidate source for volcanism in the Anahim Volcanic Belt, a 300 kilometres long chain of volcanoes and other magmatic features that have undergone erosion. This chain extends from the community of Bella Bella in the west to near the small city of Quesnel in the east. While most volcanoes are created by geological activity at tectonic plate boundaries, the Anahim hotspot is located hundreds of kilometres away from the nearest plate boundary.
The geology of the Pacific Northwest includes the composition, structure, physical properties and the processes that shape the Pacific Northwest region of North America. The region is part of the Ring of Fire: the subduction of the Pacific and Farallon Plates under the North American Plate is responsible for many of the area's scenic features as well as some of its hazards, such as volcanoes, earthquakes, and landslides.
Maitland Volcano is a heavily eroded shield volcano in the Northern Interior of British Columbia, Canada. It is 83 km (52 mi) southeast of the small community of Telegraph Creek in what is now the Klappan Range of the northern Skeena Mountains. This multi-vent volcano covered a remarkably large area and was topped by a younger volcanic edifice. Little remains of Maitland Volcano today, limited only to eroded lava flows and distinctive upstanding landforms created when magma hardened within the vents of the volcano.
The Wells Gray-Clearwater volcanic field, also called the Clearwater Cone Group, is a potentially active monogenetic volcanic field in east-central British Columbia, Canada, located approximately 130 km (81 mi) north of Kamloops. It is situated in the Cariboo Mountains of the Columbia Mountains and on the Quesnel and Shuswap Highlands. As a monogenetic volcanic field, it is a place with numerous small basaltic volcanoes and extensive lava flows.
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 and occasionally continued into geologically recent times.
A series of small volcanic earthquakes measuring less than 4.0 on the Richter magnitude scale took place in the sparsely populated Nazko area of the Central Interior of British Columbia, Canada, from October 9, 2007, to June 12, 2008. They occurred just west of Nazko Cone, a small tree-covered cinder cone that last erupted about 7,200 years ago.
The Canadian Cascade Arc, also called the Canadian Cascades, is the Canadian segment of the North American Cascade Volcanic Arc. Located entirely within the Canadian province of British Columbia, it extends from the Cascade Mountains in the south to the Coast Mountains in the north. Specifically, the southern end of the Canadian Cascades begin at the Canada–United States border. However, the specific boundaries of the northern end are not precisely known and the geology in this part of the volcanic arc is poorly understood. It is widely accepted by geologists that the Canadian Cascade Arc extends through the Pacific Ranges of the Coast Mountains. However, others have expressed concern that the volcanic arc possibly extends further north into the Kitimat Ranges, another subdivision of the Coast Mountains, and even as far north as Haida Gwaii.
The Satah Mountain volcanic field (SMVF) is an extensive north-south trending volcanic chain in the Central Interior of British Columbia that stretches south of the Itcha Range shield volcano to northeast of Nimpo Lake. The chain is located on the Chilcotin Plateau, a major subdivision of the Interior Plateau that includes other nearby volcanic features. It forms a segment of the east-west trending Anahim Volcanic Belt, whose volcanic activity ranges in age from Miocene-to-Holocene.
The Bella Bella and Gale Passage dike swarms are two parallel dike swarms on the Central Coast of British Columbia, Canada. They range in age from 14.5 to 12.5 million years old. They are both chemically bimodal, consisting of rocks such as basalt, trachyte and comendite. They form the westernmost extent of the Anahim Volcanic Belt on Athlone Island, Dufferin Island and Denny Island.
Phonotephrite or phono-tephrite is a strongly alkaline volcanic rock with a composition between phonolite and tephrite. This unusual igneous rock contains 7 to 12% alkali content and 45 to 53% silica content. It can be described as a mafic phonolite or a potassic tephrite. Phonotephrite lava flows and volcanic cones have been identified in Antarctica, Europe, North America and Africa.
The geology of Ascension Island is the geologically young, exposed part of a large volcano, 80 kilometers west of the Mid-Atlantic Ridge. The island formed within the last six to seven million years and is primarily mafic rock with some felsic rock.
The Baldface Mountain volcanic field is a volcanic field in the Central Interior of British Columbia, Canada. It is located about 25 km (16 mi) east of the Itcha Range on the Chilcotin Plateau. The volcanic field contains at least eight volcanic cones and is one of two volcanic fields in the Anahim Volcanic Belt, the other being the Satah Mountain volcanic field which extends south from the Itcha Range.
The Mount Edziza volcanic complex (MEVC) in British Columbia, Canada, has a long history of volcanism that spans more than six million years. It occurred during five cycles of magmatic activity which were characterized by 13 periods of eruptive activity. This volcanism has led to the formation of several types of volcanic landforms, including cinder cones, stratovolcanoes, subglacial volcanoes, shield volcanoes, lava domes and lava fields. The 1,000-square-kilometre (390-square-mile) plateau comprising the MEVC owes its origin to successive eruptions of highly mobile lava flows. Volcanic rocks such as alkali basalt, hawaiite, trachybasalt, benmoreite, tristanite, mugearite, trachyte, comendite and pantellerite were deposited by multiple eruptions of the MEVC; the latter eight are products of varying degrees of magmatic differentiation in underground magma reservoirs.
