Alaska’s Great Sitkin volcano erupts: US Geological Survey issues ‘red warning’ for aviation

The Alaska Volcano Observatory (AVO) and the US Geological Survey (USGS) have issued a ‘red warning’ to aviation as the Great Sitkin volcano erupts, spewing an ash plume to 15,000ft (4,600m).

In a statement on Wednesday morning, the USGS said volcanic activity on Great Sitkin Island had been confirmed by geophysical data. The volcano started erupting at 21:04 on Tuesday, with an explosion that lasted a couple of minutes, and was continuing to erupt at the time of its latest update. 

It had issued a joint ‘red warning’ to aviation with the AVO after observations suggested the ash plume was as high as 15,000ft (4,600m).

“Since that explosion, seismicity has decreased, and satellite images show that the ash cloud has detached from the vent and is moving towards the east,” the AVO said in a recent update. 

A number of photos on social media, some unverified, appear to show the ash cloud suspended over the sea and a number of remote islands. One image, probably taken from the community of Adak, approximately 26 miles (43km) west of the volcano, highlights the size of the discharge. 

The eruption had been preceded by increased volcanic-seismic unrest over the previous 24 hours, and elevated surface temperatures and sulfur dioxide had been detected over the past week.

Great Sitkin is one of the Aleutian Islands, most of which belong to the US state of Alaska, while some belong to the Russian federal subject of Kamchatka Krai. The volcano, of which there are many among the Aleutian Islands, has had a few short-lived eruptions over the past 100 years, the latest being small steam explosions in 2019. 

In January 2020, Alaska’s Mount Shishaldin sent an ash cloud 5 miles (8km) into the sky, prompting flight delays and cancelations as volcanic particles rained down on nearby communities. 

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