Warning to aviation issued following eruption on Mount Shishaldin, Alaska.

The US National Weather Service has issued a warning to aviation following an eruption on Mount  Shishaldin, a 2870 m stratovolcano (cone-shaped volcano made up of layers of ash and lava), located on Unimak Island in the Aleutian Island Chain, on Friday 14 July 2023. The volcano began erupting on Tuesday 11 July, but did not produce any major distuprion until slightly before 1.10 am local time onl Friday, when a large explosive eruption produced an ash cloud which rose to over 12 000 m above sealevel. A second eruption at about 7.10 am produced a smaller ash cloud, which on this occasion rose to about 4500 m. 

A plume of volcanic ash above Mount Shishaldin at a 10.33 am local time on Friday 14 July 2023. Matt Loewen/Alaska Volcano Observatory/United States Geological Survey/AP.

Volcanic ash is extremely hazardous to aircraft in a number of ways. At its most obvious it is opaque, both visually and to radar. Then it is abrasive, ash particles physically scour aircraft, damaging components and frosting windows. However, the ash is most dangerous when it is sucked into jet engines, here the high temperatures can melt the tiny silica particles, forming volcanic glass which then clogs engine. When this happens the only hope the aircraft has is to dive sharply, in the hope that cold air passing through the engine during the descent will cause the glass to shatter, allowing the engine to be restarted. Obviously, this is a procedure that pilots try to avoid having to perform.

Mount Shishaldin is the westernmost of three volcanoes located in an east-west line across Unimak Island. It is the largest volcano in the Aleutian Islands, and considered to be coincided to be the most symmetrical volcano on Earth, with contour lines forming near perfect circles, although the north and south slopes are steeper than the east and west slopes. The current cone structure of Mount Shishaldin is thought to be less than 10 000 years old, and is built on the remnants of an older cone, which is exposed to the west and northeast sides. To the northwest of the main volcano is an area of massive lava flows, with 24 smaller cones, thought to be parasitic on the main volcano.

The position of Mount Shshaldin on Unimak Island. Google Maps.

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth, it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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Alaska Volcano Observatory raises alert level following eruption on Mount Cleveland.

The Alaska Volcano Observatory has raised the alert level for Mount Cleveland, a 1730 m stratovolcano (cone-shaped volcano made up of layers of ash and lava), located on Chuginadak Island, roughly 500 km southeast of Anchorage in the Aleutian Island Chain, following an eruption on Monday 1 June 2020. The volcano erupted at about 10.30 pm local time (about 7.30 am on Tuesday 2 June, GMT), producing an ash column that rose to an altitude of about 6700 m, which drifted to the south and quickly dissapated. This is the first eruption since January 2019, representing the longest pause between eruptions since the current cycle of activity began, 20 years ago.

The location of Mount Cleveland. Google Maps.

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

 How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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Eruption on Mount Shishaldin, Alaska.

The Alaska Volcano Observatory has reported a large eruption on Mount Shishaldin, a 2870 m stratovolcano (cone-shaped volcano made up of layers of ash and lava), located on Unimak Island in the Aleutian Island Chain. The volcano began erupting some time before 9.50 am on Friday 3 January 2020 (when the eruption was first observed by a pilot), and produced an ash column that rose to about 8000 m above sealevel, and drifted to the south. The eruption is not thought to present any threat to Human life or habitation, due to the remote location of the volcano, but a warning has been issued to aviation. This is the latest in a series of eruptions on the mountain that began in October 2019.

An eruption on Mount Shishaldin on 26 December 2019. Aslaska Volcano Observatory.

Mount Shishaldin is the westernmost of three volcanoes located in an east-west line across Unimak Island. It is the largest volcano in the Aleutian Islands, and considered to be coincided to be the most symmetrical volcano on Earth, with contour lines forming near perfect circles, although the north and south slopes are steeper than the east and west slopes. The current cone structure of Mount Shishaldin is thought to be less than 10 000 years old, and is built on the remnants of an older cone, which is exposed to the west and northeast sides. To the northwest of the main volcano is an area of massive lava flows, with 24 smaller cones, thought to be parasitic on the main volcano.

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

 How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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Eruption on Mount Cleveland, Alaska.

The Alaska Volcano Observatory reported am eruption on Mount Cleveland, a 1730 m stratovolcano (cone-shaped volcano made up of layers of ash and lava, located on Chuginadak Island, roughly 500 km southeast of Anchorage in the Aleutian Island Chain, slightly before 6.00 am Alaskan Time (slightly before 3.00 pm GMT) on Friday 2 March 2018. The eruption produced an ash column that rose to an altitude of about 4500 m, and drifted to the northeast.

The location of Mount Cleveland. Google Maps.

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

 How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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Eruptive Activity on Great Sisken Island.

The Alaska Volcano Observatory reported a vapour plume rising 300 m about the summit of Great Sitkin, a volcanic island in the Andreanof Islands, part of the Aleutian Island chain, on Sunday 19 November 2017. This is the first observed eruptive activity on the volcano since February 1974, though it is not entirely unexpected, as there has been a steady increase in seismic activity beneath the island since July 2016. Seismic activity beneath volcanoes can be significant, as they are often caused by the arrival of fresh magma, which may indicate that a volcano is about to undergo an eruptive episode. A second small plume was spotted over the island by a satellite on Tuesday 21 November.

 Small plume over Great Siskin Island on 19 November 2017. Alaska Volcano Observatory.

  

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

 How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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Aviation warning issued after eruption on Bogoslof Island, Alaska.

The Alasaka Volcano Observatory issued a warning to aviation following an eruption on Bogoslof Island in the Aluetian Chain on the morning of Monday 7 August 2017. The eruption produced an ash column which rose to over 9750 m above the uninhabited island. This is the latest in a series of eruptions that began in December last year, many of which have produced ash columns that rose to heights of over 6000 m, the trigger point for aviation warnings in the Aleutian Islands.

The approximate location of Bogoslof Island. Google Maps. 

Bogoslof Island is uninhabited, and the islands around is are home to at most sparse Human populations, however it still presents a serious threat to air-traffic, as the Aleutian Islands lie in the path of a number of commercial aircraft routes, connecting the US to East Asia. Volcanic ash is extremely hazardous to aircraft in a number of ways. At its most obvious it is opaque, both visually and to radar. Then it is abrasive, ash particles physically scour aircraft, damaging components and frosting windows. However the ash is most dangerous when it is sucked into jet engines, here the high temperatures can melt the tiny silica particles, forming volcanic glass which then clogs engine. When this happens the only hope the aircraft has is to dive sharply, in the hope that cold air passing through the engine during the descent will cause the glass to shatter, allowing the engine to be restarted. Obviously this is a procedure that pilots try to avoid having to perform.

Bogoslof Island forms the tip of a submarine volcano that rises from the Bering Sea floor, 1.8 km below the surface. The island only rises 150 m above the surface, but is 1.76 km in length and 500 m wide, forming part of the rim of the caldera (crater) of the volcano; all eruptive activity occurs beneath the surface to the northeast of the island itself. The nature of the island means that it is frequently reshaped by eruptions.

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

 How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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Further eruption on Bogoslof Island leads to new aviation warning.

The Alasaka Volcano Observatory issued a warning to aviation following an eruption on Bogoslof Island in the Aluetian Chain on the morning of Saturday 10 June 2017. The eruption produced an ash column which rose to over 9000 m above the uninhabited island. This is the latest in a series of eruptions that began in December last year, many of which have produced ash columns that rose to heights of over 6000 m, the trigger point for aviation warnings in the Aleutian Islands.

Satellite image of an ash column over Bogoslof on 5 June 2017, taken with the Operational Land Imager on the Landsat-8 satellite. NASA.

Bogoslof Island is uninhabited, and the islands around is are home to at most sparse Human populations, however it still presents a serious threat to air-traffic, as the Aleutian Islands lie in the path of a number of commercial aircraft routes, connecting the US to East Asia. Volcanic ash is extremely hazardous to aircraft in a number of ways. At its most obvious it is opaque, both visually and to radar. Then it is abrasive, ash particles physically scour aircraft, damaging components and frosting windows. However the ash is most dangerous when it is sucked into jet engines, here the high temperatures can melt the tiny silica particles, forming volcanic glass which then clogs engine. When this happens the only hope the aircraft has is to dive sharply, in the hope that cold air passing through the engine during the descent will cause the glass to shatter, allowing the engine to be restarted. Obviously this is a procedure that pilots try to avoid having to perform.

Bogoslof Island forms the tip of a submarine volcano that rises from the Bering Sea floor, 1.8 km below the surface. The island only rises 150 m above the surface, but is 1.76 km in length and 500 m wide, forming part of the rim of the caldera (crater) of the volcano; all eruptive activity occurs beneath the surface to the northeast of the island itself. The nature of the island means that it is frequently reshaped by eruptions.

 The approximate location of Bogoslof Island. Google Maps.

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

  How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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