Producing content you read on this website takes a lot of time, effort, and hard work. If you value what we do here, please consider subscribing today.
The Alaska Volcano Observatory raised the Aviation Color Code for Semisopochnoi stratovolcano to Yellow and the Volcano Alert Level to Advisory on September 16, 2018. This is the largest subaerial volcano of the western Aleutians. It's 20 km (12.4 miles) wide at sea level and contains an 8 km (5 miles) wide caldera.
An increase in seismicity beginning 16:31 UTC (08:31 AKDT) on September 16 has prompted AVO to raise the Aviation Color Code and Volcano Alert Level to Yellow/Advisory.
There is no clear indication from satellite imagery or regional infrasound data that Semisopochnoi is erupting at this time, AVO said, adding it will continue to monitor Semisopochnoi seismic data and evaluate satellite images.
The last known eruption of this volcano took place in 1987. It had Volcanic Explosivity Index of 2. The previous confirmed eruption was in 1873.
Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km (12.4 miles) wide at sea level and contains an 8-km-wide (5 miles) caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1221-m-high (4 005 feet) Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part.
The three-peaked 774-m-high (2 539 feet) Mount Cerberus volcano was constructed during the Holocene within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side.
Other post-caldera volcanoes include the symmetrical 855-m-high (2 903 feet) Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera.
Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time.
This volcano is located within the Aleutian Islands, a UNESCO Biosphere Reserve property.
Featured image credit: Google, TW
Register/become a supporter
Your support is crucial for our survival. It makes this project fully self-sustainable and keeps us independent and focused on the content we love to create and share.
You'll receive your ad-free account for 20x faster browsing experience, clean interface without any distractions, ability to post comments without prior editorial check, all our desktop and mobile applications (current and upcoming) ad-free and with the full set of features available, a direct line of communication and much more. See all options.