Milbanke Sound Group

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Milbanke Sound Group
Milbanke Sound Cones
Milbanke Sound Group.jpg
Aerial photo of the Milbanke Sound Group
Highest point
Peak Helmet Peak [1]
Elevation 335 m (1,099 ft)
Coordinates 52°21′17″N128°21′01″W / 52.35472°N 128.35028°W / 52.35472; -128.35028
Geography
CountryCanada
Province British Columbia
DistrictRange 3 Coast Land District
Parent range Kitimat Ranges
Geology
Age of rock Formation: In the past 10,000 years (Holocene) [2]
Last eruption: Unknown [3]
Last activity: Unknown [3]
Type of rock Cinder cones, lava flows [3]

The Milbanke Sound Group, also called the Milbanke Sound Cones, is an enigmatic group of five small basaltic volcanoes in the Kitimat Ranges of the Coast Mountains in British Columbia, Canada. Named for Milbanke Sound, this volcanic group straddles on at least four small islands (three of which are uninhabited), including Swindle, Price, Lady Douglas and Lake Island. Not much is known about this group of volcanoes and they remain undated. [4] However, they all likely formed in the past 10,000 years after the last glacial period as evidenced by a small amount of erosion. [2] The age of the most recent volcanic activity is also unknown. [3] Most of the Milbanke Sound Cones are covered by mature forest. Kitasu Hill and Helmet Peak are the only two cones that are officially named.

Contents

This group of volcanoes is unlike many other volcanic groups in Canada as it resides on islands instead of on the mainland. The volcanoes form a northwest-southeast trend along the British Columbia Coast. To the west the Milbanke Sound Group is bounded by the Pacific Ocean and elsewhere it is surrounded by adjacent islands that form an archipelago. Although not related, the Milbanke Sound Group is close to the remains of a much older magmatic feature that was formed during the Tertiary period. [3]

Geology

Volcanoes

Just south of Kitasu Bay on the southwestern shore of Swindle Island, Kitasu Hill rises with an elevation of 250 m (820 ft) and a topographic prominence of 230 m (750 ft). This is a small symmetrical monogenetic cinder cone and the best preserved volcano associated with the Milbanke Sound Group. [2] [5] It is the northernmost and most prominent volcano of the Milbanke Sound Cones with a circular volcanic crater at its summit. [2] The volcano produced basaltic lava flows that extend to the north. [3] Subaerial tephra and volcanic bombs are the main volcanics comprising the volcano. [2] These volcanics surround eroded remains of the basalt lava flows and are composed of the mineral olivine. [2] Kitasu Hill rests on till that overlies glacially scoured bedrock. [4]

Satellite image of Kitasu Hill and its circular volcanic crater Kitasu Hill.jpg
Satellite image of Kitasu Hill and its circular volcanic crater

Near the northeastern shore of Price Island, a small eroded monogenetic cinder cone composed of basalt is covered by mature forest. [4] [6] It has an elevation of 40 m (130 ft) and is the source of a basaltic lava flow. [1] [4] This lava flow extends down to the northeastern shoreline of Price Island where it covers beach gravel. [4]

Helmet Peak on the northern end of Lake Island just off the southwestern side of the Don Peninsula is a steep-sided monogenetic cinder cone. [7] [8] It is composed of welded volcanic blocks and basaltic feeder dikes. [4] With an elevation of 335 m (1,099 ft), Helmet Peak is the highest volcano in the Milbanke Sound Group. [2] During its eruption, basaltic tuff breccia was sent throughout the surrounding landscape that deposited on glaciated granitic rock and unconsolidated beach gravel near the volcano. [4] This basaltic tuff breccia covers parts of Lake Island and nearby Lady Douglas Island. [2] Blocks of basement granodiorite, some up to 2 m (6.6 ft) wide, are randomly suspended within the breccia. [4] Basalt on Lake Island is characterized by abundant 0.5 cm (0.20 in) to 1 cm (0.39 in) labradorite and clinopyroxene phenocrysts. [4]

At the southern end of the Milbanke Sound Group, a small monogenetic cinder cone with an elevation of 50 m (160 ft) resides on Dufferin Island. [1] [9] It sent basaltic lava flows to the north where they reached the island's shoreline to cover beach gravel. [4] Since its formation, the cinder cone has been eroded and covered by forest. [9] Finngal Island, south of Dufferin Island, contains one or more basaltic lava flows that form well-preserved columnar jointing. [2] [10] Like other volcanic deposits in the Milbanke Sound Group, little is known about these lava flows. [10]

Origins

The relationship of the Milbanke Sound Cones and to other volcanoes throughout British Columbia is not clear. [2] In some classifications, they are grouped with the Anahim Volcanic Belt because they are parallel with its east-west trend. [2] However, this grouping is not widely accepted because the volcanoes are much younger than other magmatic features at the western end of the Anahim Volcanic Belt. [2] The cause of this significant age change is because the Anahim Volcanic Belt has its origins from the North American Plate moving over the hypothesized Anahim hotspot. [2] This is a mantle plume that is likely responsible for volcanism throughout the Anahim Volcanic Belt. [2] Individual Anahim volcanoes generally become older west of Nazko Cone, indicating that the North American Plate is moving in a westerly direction with respect to the hotspot, carrying the volcanoes along with it at a rate of 2 cm (0.79 in) to 3.3 cm (1.3 in) per year. [11] Thus the hotspot model can not be used to explain the formation of the Milbanke Sound Group. [2] However, the volcanic group is near the remnants of a 14 to 12 million year old magmatic feature that is interpreted to define the westernmost end of the Anahim hotspot track. [4]

A possible explanation for the origin of the Milbanke Sound Group is that it reflects a northern extension of the north-west trending subduction-related Garibaldi Volcanic Belt further south. [2] This in turn is a segment of the Cascade Volcanic Arc in the United States, which includes Mount Baker and Mount St. Helens. [12] However, there is currently not enough data to support this suggestion. [2] Its origins might also result from other tectonic processes that are currently not understood. [2]

Monitoring

Currently, the Milbanke Sound Cones are not monitored closely enough by the Geological Survey of Canada to ascertain how active their magma chambers are. [13] An existing network of seismographs has been established to monitor earthquakes, but is too far away to provide a good indication of what is happening beneath the cones. [13] It may sense an increase in activity if a volcano becomes very restless, but this may only provide a warning for a large eruption. [13] It might detect activity only once a volcano has started erupting. [13]

The Interagency Volcanic Event Notification Plan, Canada's volcanic emergency notification program, was established to outline the notification procedure of some of the main agencies that would be involved in response to a volcanic eruption in Canada, an eruption close to Canada's borders, or an eruption significant enough to have an effect on Canada and its people. [14] It focuses primarily on aviation safety because jet aircraft can quickly enter areas of volcanic ash. [15] The program notifies all impacted agencies that have to deal with volcanic events. [15] Aircraft are rerouted away from hazardous ash and people on the ground are notified of potential ash fall. [15]

See also

Related Research Articles

<span class="mw-page-title-main">Anahim Volcanic Belt</span> Chain of volcanoes and related magmatic features in British Columbia, Canada

The Anahim Volcanic Belt (AVB) is a west–east trending chain of volcanoes and related magmatic features in British Columbia, Canada. It extends from Athlone Island on the Central Coast, running eastward through the strongly uplifted and deeply dissected Coast Mountains to near the community of Nazko on the Interior Plateau. The AVB is delineated as three west-to-east segments that differ in age and structure. A wide variety of igneous rocks with differing compositions occur throughout these segments, comprising landforms such as volcanic cones, volcanic plugs, lava domes, shield volcanoes and intrusions.

<span class="mw-page-title-main">Garibaldi Volcanic Belt</span> Volcanic chain in southwestern British Columbia, Canada

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.

<span class="mw-page-title-main">Chilcotin Group</span> Large area of basaltic lava in south-central British Columbia, Canada

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.

<span class="mw-page-title-main">Northern Cordilleran Volcanic Province</span> 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. It has formed due to extensional cracking of the North American continent—similar to other on-land extensional volcanic zones, including the Basin and Range Province and the East African Rift. Although taking its name from the Western Cordillera, this term is a geologic grouping rather than a geographic one. The southmost part of the NCVP has more, and larger, volcanoes than does the rest of the NCVP; further north it is less clearly delineated, describing a large arch that sways westward through central Yukon.

<span class="mw-page-title-main">Nazko Cone</span> Active volcano in British Columbia, Canada

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.

<span class="mw-page-title-main">Itcha Range</span> Mountain range in British Columbia, Canada

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.

<span class="mw-page-title-main">Volcanism of Canada</span> Volcanic activity in Canada

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.

<span class="mw-page-title-main">Ilgachuz Range</span> Extinct volcano in British Columbia, Canada

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.

<span class="mw-page-title-main">Geology of the Pacific Northwest</span> Geology of Oregon and Washington (United States) and British Columbia (Canada)

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.

<span class="mw-page-title-main">Cinder cone</span> Steep hill of pyroclastic fragments around a volcanic vent

A cinder cone is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone that often is symmetrical; with slopes between 30 and 40°; and a nearly circular ground plan. Most cinder cones have a bowl-shaped crater at the summit.

<span class="mw-page-title-main">Price Island</span>

Price Island is an island on the coast of the Canadian province of British Columbia. It is located at the southeastern end of Hecate Strait and the northeastern end of Queen Charlotte Sound. The southernmost point of Price Island, called Day Point, is used to delineate the boundary between Hecate Strait and Queen Charlotte Sound. Milbanke Sound is just to the south of Price Island. Laredo Sound is just north. Swindle Island lies just north of Price Island. The main Inside Passage route crosses Milbanke Sound and enters Finlayson Channel just east of Price Island. Price Island is located within the Kitimat-Stikine Regional District.

<span class="mw-page-title-main">Swindle Island</span>

Swindle Island is an island on the North Coast of the Canadian province of British Columbia. It is located south of Princess Royal Island on the Inside Passage shipping route. The small First Nations community of Klemtu is located on its eastern side across from Cone Island. Price Island lies just south of Swindle Island. Both are located within the Kitimat-Stikine Regional District. Swindle Island's southernmost extremity is Jorkins Point, which lies at the confluence of Milbanke Sound and Finlayson Channel.

<span class="mw-page-title-main">Wells Gray-Clearwater volcanic field</span> Volcanic field in British Columbia, Canada

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.

<span class="mw-page-title-main">Volcanism of Western Canada</span>

Volcanism of Western Canada has produced lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, greenstone belts, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.

<span class="mw-page-title-main">The Volcano (British Columbia)</span> Mountain in British Columbia, Canada

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 km (40 mi) northwest of the small community of Stewart near the head of Lava Fork. With a summit elevation of 1,656 m (5,433 ft) 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.

<span class="mw-page-title-main">Volcanic history of the Northern Cordilleran Volcanic Province</span>

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.

<span class="mw-page-title-main">Canadian Cascade Arc</span> Canadian segment of the North American Cascade Volcanic Arc

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.

References

  1. 1 2 3 "Milbanke Sound Group". Global Volcanism Program . Smithsonian Institution . Retrieved 2010-01-30.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 "Anahim Volcanic Belt: Milbanke Sound cones". Catalogue of Canadian volcanoes. Geological Survey of Canada. 2009-04-14. Archived from the original on 2011-06-04. Retrieved 2010-01-30.
  3. 1 2 3 4 5 6 "Milbanke Sound Group". Global Volcanism Program . Smithsonian Institution . Retrieved 2010-01-30.
  4. 1 2 3 4 5 6 7 8 9 10 11 Wood, Charles A.; Kienle, Jürgen (1990). Volcanoes of North America: United States and Canada. Cambridge, England: Cambridge University Press. p. 130. ISBN   0-521-43811-X.
  5. ↑ "Kitasu Hill". Catalogue of Canadian volcanoes. Geological Survey of Canada. 2009-03-10. Archived from the original on 2010-12-11. Retrieved 2010-01-30.
  6. ↑ "Price Island". Catalogue of Canadian volcanoes. Geological Survey of Canada. 2009-03-10. Archived from the original on 2010-12-11. Retrieved 2010-01-30.
  7. ↑ "Helmet Peak". Catalogue of Canadian volcanoes. Geological Survey of Canada. 2009-03-10. Archived from the original on 2010-12-11. Retrieved 2010-01-30.
  8. ↑ "Helmet Peak". BC Geographical Names .
  9. 1 2 "Dufferin Island". Catalogue of Canadian volcanoes. Geological Survey of Canada. 2009-03-10. Archived from the original on 2010-12-11. Retrieved 2010-01-30.
  10. 1 2 "Finngal Island". Catalogue of Canadian volcanoes. Geological Survey of Canada. 2009-03-10. Archived from the original on 2010-12-11. Retrieved 2010-01-31.
  11. ↑ Bevier, Mary Lou; Armstrong, Richard Lee; Souther, J. G. (August 1979). "Miocene peralkaline volcanism in west-central British Columbia — Its temporal and plate-tectonics setting". Geology. Astrophysics Data System. 7 (8): 389–392. Bibcode:1979Geo.....7..389B. doi:10.1130/0091-7613(1979)7<389:MPVIWB>2.0.CO;2.
  12. ↑ "Garibaldi Volcanic Belt". Catalogue of Canadian volcanoes. Geological Survey of Canada. 2009-04-02. Archived from the original on 2011-06-04. Retrieved 2010-02-04.
  13. 1 2 3 4 "Monitoring volcanoes". Volcanoes of Canada. Geological Survey of Canada. 2008-02-12. Archived from the original on 2008-05-07. Retrieved 2009-01-22.
  14. ↑ "Interagency Volcanic Event Notification Plan: Western Canada" (PDF). Natural Resources Canada. 2008-05-01. p. 7. Archived from the original (PDF) on 2011-06-04. Retrieved 2009-02-19.
  15. 1 2 3 "Volcanoes". Natural Resources Canada. 2007-09-05. Archived from the original on 2009-02-17. Retrieved 2009-01-22.
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