Pyramid Formation | |
---|---|
Stratigraphic range: | |
Type | Geological formation [1] |
Unit of | Mount Edziza volcanic complex [2] |
Underlies | Ice Peak Formation, Edziza Formation [1] |
Overlies | Nido Formation [1] |
Lithology | |
Primary | Trachyte, comendite, pantellerite [1] |
Other | Basalt [1] |
Location | |
Coordinates | 57°30′N130°36′W / 57.5°N 130.6°W [2] |
Region | British Columbia [1] |
Country | Canada [1] |
Type section | |
Named for | The Pyramid [1] |
Named by | Souther et al., 1984 [3] |
The Pyramid Formation is a stratigraphic unit of Pleistocene age in northwestern British Columbia, Canada.
The Pyramid Formation takes its name from The Pyramid, a prominent pyramid-shaped lava dome on the northeastern flank of Mount Edziza. [1] [4]
Two subunits comprise the Pyramid Formation. The lower unit is a basal pyroclastic member up to 3 m (9.8 ft) thick. It contains trachytic pumice, sodic pyroxene and alkali feldspar; the latter two are present in the form of lithic clasts and crystals. This unit is rusty brown in colour and was deposited by a pyroclastic surge. The upper unit consists of a basalt member up to 65 m (213 ft) thick. It includes 6 to 10 individual basalt flows that reach thicknesses of 3–20 m (9.8–65.6 ft). They appear to have been deposited almost immediately after the pyroclastic surge was erupted. [1] Several silicic lava domes and minor lava flows of the Pyramid Formation postdate the basalt member. Among the silicic domes are Sphinx Dome, Pharaoh Dome and The Pyramid. [5]
The Pyramid Formation has a volume of 11.4 km3 (2.7 cu mi), making it the eighth most voluminous geological formation of the Mount Edziza volcanic complex after the Little Iskut Formation. [1] [2] It overlies the Nido Formation and underlies the Ice Peak and Edziza formations, all of which have formed in the last 8 million years. K–Ar dating of the Pyramid Formation has yielded ages of 1.2 ± 0.4 million years and 1.20 ± 0.03 million years for comenditic glass and 0.94 ± 0.12 million years and 0.94 ± 0.05 million years for trachyte. [1]
The Garibaldi Volcanic Belt is a northwest–southeast trending volcanic chain in the Pacific Ranges of the Coast Mountains that extends from Watts Point in the south to the Ha-Iltzuk Icefield in the north. This chain of volcanoes is located in southwestern British Columbia, Canada. It forms the northernmost segment of the Cascade Volcanic Arc, which includes Mount St. Helens and Mount Baker. Most volcanoes of the Garibaldi chain are dormant stratovolcanoes and subglacial volcanoes that have been eroded by glacial ice. Less common volcanic landforms include cinder cones, volcanic plugs, lava domes and calderas. These diverse formations were created by different styles of volcanic activity, including Peléan and Plinian eruptions.
Mount Edziza, sometimes called Edziza Mountain or Edziza Peak, is a stratovolcano in Cassiar Land District of northwestern British Columbia, Canada. It is located on the Big Raven Plateau of the Tahltan Highland which extends along the western side of the Stikine Plateau. The mountain has an elevation of 2,786 metres, making it the highest volcano of the Mount Edziza volcanic complex. However, it had an elevation of at least 3,396 metres before its original summit was likely destroyed by a violent, climactic eruption in the geologic past; its current flat summit contains an ice-filled, 2-kilometre (1.2-mile) in diameter crater. Mount Edziza contains several lava domes, cinder cones and lava fields on its flanks, as well as an ice cap that is characterized by several outlet glaciers stretching out to lower altitudes. All sides of the mountain are drained by tributaries of Mess Creek and Kakiddi Creek which are situated within the Stikine River watershed.
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.
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.
Tennena Cone, alternatively Icebridge Cone, is a small volcanic cone in Cassiar Land District of northwestern British Columbia, Canada. It has an elevation of 2,390 metres and lies on the western flank of Ice Peak, the prominent south peak of Mount Edziza. The cone is almost completely surrounded by glacial ice of Mount Edziza's ice cap which covers an area of around 70 square kilometres. Tennena Cone is 200 metres high, 1,200 metres long and up to 600 metres wide, its symmetrical structure resembling a black pyramid. The cone and the surrounding area lies in Mount Edziza Provincial Park which also includes the Spectrum Range to the south.
The Mount Edziza volcanic complex is a group of volcanoes and associated lava flows in northwestern British Columbia, Canada. Located on the Tahltan Highland, it is 40 kilometres southeast of Telegraph Creek and 85 kilometres southwest of Dease Lake. The complex encompasses a broad, steep-sided lava plateau that extends over 1,000 square kilometres. Its highest summit is 2,786 metres in elevation, making the MEVC the highest of four large complexes in an extensive north–south trending volcanic region. It is obscured by an ice cap characterized by several outlet glaciers that stretch out to lower altitudes.
The Mess Lake Lava Field is a volcanic field associated with the Mount Edziza volcanic complex of the Northern Cordilleran Volcanic Province in northwestern British Columbia, Canada. It lies northwest of the Spectrum Range on the Kitsu Plateau and consists of young basaltic lava flows and tephra. The source for the basaltic lava and tephra was three cinder cones, including Mess Lake Cone and The Ash Pit, which may be the youngest volcanic feature of the Mount Edziza volcanic complex.
The Little Iskut Formation is a stratigraphic unit of Miocene age in northwestern British Columbia, Canada.
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.
Jack Gordon Souther was an American-born Canadian geologist, volcanologist, professor and engineer. He contributed significantly to the early understanding of recent volcanic activity in the Canadian Cordillera. Many of his publications continue to be regarded as classics in their field, even now several decades after they were written.
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 Armadillo Formation is a stratigraphic unit of Miocene age in northwestern British Columbia, Canada.
The Nido Formation is a stratigraphic unit of Neogene age in northwestern British Columbia, Canada.
The Big Raven Formation is a stratigraphic unit of Quaternary age in northwestern British Columbia, Canada. It is the youngest and least voluminous geological formation of the Mount Edziza volcanic complex (MEVC); it overlies at least six older formations of this volcanic complex. The main volcanic rocks of the Big Raven Formation are alkali basalts and hawaiites, although a small volume of trachyte comprises the Sheep Track Member. These rocks were deposited by volcanic eruptions in the last 20,000 years during the latest magmatic cycle of the MEVC. Alkali basalt and hawaiite are in the form of lava flows and small volcanic cones while trachyte of the Sheep Track Member is mainly in the form of volcanic ejecta which covers an area of about 40 square kilometres.
The Klastline Formation is a stratigraphic unit of Pleistocene age in northwestern British Columbia, Canada.
The Mount Edziza volcanic complex (MEVC) in British Columbia, Canada, has a long history of volcanism that spans more than 6 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 basalt, trachybasalt, benmoreite, tristanite, mugearite, trachyte and rhyolite were deposited by multiple eruptions of the MEVC; the latter seven rock types are products of varying degrees of magmatic differentiation in underground magma reservoirs. At least 10 distinct flows of obsidian were produced by volcanism of the MEVC, some of which were exploited by indigenous peoples in prehistoric times to make tools and weaponry. Renewed volcanism could produce explosive eruptions and block local streams with lava flows.
Tennaya Glacier is one of several glaciers draining the eastern side of the Mount Edziza ice cap in northwestern British Columbia, Canada. It is located southeast of the summit of Mount Edziza and northwest of Ice Peak at the head of Tennaya Creek. Meltwater from Tennaya Glacier feeds Tennaya Creek which eventually flows into Nuttlude Lake, an expansion of Kakiddi Creek.
Idiji Glacier is one of several glaciers draining the eastern side of the Mount Edziza ice cap in northwestern British Columbia, Canada. It is located south of the summit of Mount Edziza in a cirque just southeast of Ice Peak. Idiji Glacier is separated from the much larger Tencho Glacier by a ridge that extends south of Ice Peak above the Idiji cirque headwall. Idiji Glacier is the namesake of Idiji Ridge which is just to the southeast.
The Edziza Formation is a stratigraphic unit of Pleistocene age in northwestern British Columbia, Canada. First described in 1984, the Edziza Formation was mapped as one of several geological formations of the Mount Edziza volcanic complex. It overlies at least four other geological formations of this volcanic complex that differ in age and composition. The main volcanic rock comprising the Edziza Formation is trachyte which was deposited by volcanic eruptions at the end of the third magmatic cycle of the Mount Edziza volcanic complex 0.9 million years ago.
Idiji Ridge is a mountain ridge extending east of Tencho Glacier on the southern flank of Mount Edziza in northwestern British Columbia, Canada. It is bounded on the south by a valley containing an unnamed valley, on the east by Tennaya Creek valley and on the north by cirques extending east of Ice Peak. Idiji Ridge takes its name from the adjacent Idiji Glacier; Idiji means "it thunders" in the Tahltan language.