(video taken by Ian Erickson & provided by the Alaska Volcano Observatory)
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Shishaldin Volcano is a subduction zone stratovolcano on Unimak Island in the Aleutian Islands of Alaska. Minor lava eruptions in the summit crater started on 12 July 2023. Twelve episodes of explosive ash eruptions have occurred since then, on 14 July, 15 July, 18 July, 22-23 July, 25-26 July, 4 August, 14-15 August, 25 August, 5 September, 15 September, 24 to 25 September, and 3 October 2023. This video shows minor lava eruptive activity at Shishaldin's summit on 12 July 2023.

The Aleutian Arc is a subduction zone formed as the Pacific Plate dives underneath the North American Plate (this area is sometimes called the Bering Plate). The diving plate in subduction zones releases water at depth, which causes partial melting of overlying mantle rocks. The low-density melt rises and eventually reaches the surface, forming volcanoes. All subduction zones have volcanoes and frequent seismicity. Volcanoes in such settings tend to have explosive ash eruptions. Rocks and tephra deposits at subduction zone volcanoes are usually intermediate in composition - typically andesitic to dacitic.
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Info. at:
en.wikipedia.org/wiki/Mount_Shishaldin
and
en.wikipedia.org/wiki/Aleutian_Arc

Tags:   Shishaldin Volcano subduction zone volcanoes Aleutian Aleutians Arc Alaska July 2023 lava eruption eruptions Unimak Island summit stratovolcano stratovolcanoes composite video videos

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This seismogram is from the Shishaldin Broadband A seismic station on Unimak Island in the Aleutians of Alaska, USA. The thick noise in the top third of the graph is seismicity ("volcanic tremor") at Shishaldin Volcano, a subduction zone stratovolcano on Unimak Island in the late evening of 13 July 2023. The very thick noise on the 00:30 to 02:00 lines represents explosive ash eruptions from Shishaldin. Notable explosions occurred at 1:09 AM and 1:36 AM, local time, on 14 July 2023. The Alaska Volcano Observatory reported ash clouds from this activity reaching 9 to 12 kilometers above sea level - that's 30 to 40 thousand feet high - and drifted over the Pacific Ocean. This explosive activity was preceded by minor lava eruptions in Shishaldin's summit crater on 12 and 13 July 2023.

Tags:   Shishaldin Volcano subduction zone volcanoes Aleutian Aleutians Arc Alaska July 2023 explosive ash eruption eruptions seismicity earthquake earthquakes quake quakes volcanic tremor Unimak Island seismogram seismograms

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(image provided by the Alaska Volcano Observatory; original photo taken by Lee Cooper from a Canadian coast guard vessel)
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Shishaldin Volcano is a subduction zone stratovolcano on Unimak Island in the Aleutian Islands of Alaska. Minor lava eruptions in the summit crater started on 12 July 2023. Twelve episodes of explosive ash eruptions have occurred since then, on 14 July, 15 July, 18 July, 22-23 July, 25-26 July, 4 August, 14-15 August, 25 August, 5 September, 15 September, 24 to 25 September, and 3 October 2023. Seen here is ash erupting from Shishaldin on 14 July 2023.

The Aleutian Arc is a subduction zone formed as the Pacific Plate dives underneath the North American Plate (this area is sometimes called the Bering Plate). The diving plate in subduction zones releases water at depth, which causes partial melting of overlying mantle rocks. The low-density melt rises and eventually reaches the surface, forming volcanoes. All subduction zones have volcanoes and frequent seismicity. Volcanoes in such settings tend to have explosive ash eruptions. Rocks and tephra deposits at subduction zone volcanoes are usually intermediate in composition - typically andesitic to dacitic.
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Info. at:
en.wikipedia.org/wiki/Mount_Shishaldin
and
en.wikipedia.org/wiki/Aleutian_Arc

Tags:   July 2023 Shishaldin Volcano stratovolcano stratovolcanoes composite volcanoes Aleutian Arc Aleutians Alaska ash eruption eruptions

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(video taken by Robbie Armijo & provided by the Alaska Volcano Observatory)
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Shishaldin Volcano is a subduction zone stratovolcano on Unimak Island in the Aleutian Islands of Alaska. Minor lava eruptions in the summit crater started on 12 July 2023. Twelve episodes of explosive ash eruptions have occurred since then, on 14 July, 15 July, 18 July, 22-23 July, 25-26 July, 4 August, 14-15 August, 25 August, 5 September, 15 September, 24 to 25 September, and 3 October 2023. This video shows fresh, dark-colored ash and lahar deposits at Shishaldin on 14 July 2023, which contrasts with the bright white surface snow a couple days earlier.

The Aleutian Arc is a subduction zone formed as the Pacific Plate dives underneath the North American Plate (this area is sometimes called the Bering Plate). The diving plate in subduction zones releases water at depth, which causes partial melting of overlying mantle rocks. The low-density melt rises and eventually reaches the surface, forming volcanoes. All subduction zones have volcanoes and frequent seismicity. Volcanoes in such settings tend to have explosive ash eruptions. Rocks and tephra deposits at subduction zone volcanoes are usually intermediate in composition - typically andesitic to dacitic.
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Info. at:
en.wikipedia.org/wiki/Mount_Shishaldin
and
en.wikipedia.org/wiki/Aleutian_Arc

Tags:   Shishaldin Volcano subduction zone volcanoes Aleutian Aleutians Arc Alaska July 2023 ash eruption eruptions lahar lahars Unimak Island summit stratovolcano stratovolcanoes composite video videos

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This seismogram is from the Shishaldin Broadband A seismic station on Unimak Island in the Aleutians of Alaska, USA. Starting with the 17:00 line, the slightly thick to thick noise is seismicity ("volcanic tremor") at Shishaldin Volcano, a subduction zone stratovolcano on Unimak Island in the late afternoon to evening of 15 July 2023. Starting around 9:00 PM (the 21:00 line on the graph), local time, 15 July 2023, explosive eruptive activity commenced with many explosion events occurring in the late evening. The Alaska Volcano Observatory reported a 125+ kilometers long ash plume drifting ~southeast-ward over the Pacific Ocean, at a height of about 5 kilometers - that's about 16,000 feet high. Some individual explosion events have sent ash clouds about 6 kilometers high - that's about 20,000 feet.

Explosive eruptive activity at Shishaldin also occurred in the early morning of 14 July 2023. Minor lava eruptions occurred in the summit crater on 12 and 13 July 2023.

The large block of red on the 22:30 line is from a magnitude 7.2 subduction zone earthquake south of the Alaska Peninsula. This event is unrelated to Shishaldin's volcanic eruptions.

Tags:   Shishaldin Volcano subduction zone volcanoes Aleutian Aleutians Arc Alaska July 2023 explosive ash eruption eruptions seismicity earthquake earthquakes quake quakes volcanic tremor Unimak Island seismogram seismograms

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