File:Shishaldin Volcano (27 August 2023) (Aleutian Arc, Alaska, USA) 1.jpg

English: (public domain photo by Darren Tan & 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. Eight 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, and 25 August 2023.

Seen here is Shishaldin on 27 August 2023, a couple days after an ash eruption. The volcano is usually mostly covered in white snow - the blackish material here is fresh tephra deposited atop the snow. The dark material in the sky to the right of the volcano is fine-grained tephra from a rim collapse event. Click on the photo to zoom in - the summit area has white steam plumes from active fumaroles.

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