Eruption detected at Semisopochnoi volcano, Alaska

Eruption detected at Semisopochnoi volcano, Alaska

An eruption signature was detected at Semisopochnoi as strong tremor on local seismic and in regional infrasound networks on Adak Island, Alaska Volcano Observatory reported at 10:25 UTC on December 7, 2019.

The event started at 09:26 UTC (00:26 AKST) on December 7 and has continued with and ongoing but weaker local seismic signal. Any volcanic ash emissions are most likely low-level at this time.

The meteorological cloud deck has been around 3 000 m (10 000 feet) above sea level over Semisopochnoi and no ash signals have been detected above this height. Nothing has been detected in lightning data, AVO said.

The Volcano Alert Level was raised from Watch to Advisory and the Aviation Color Code from Yellow to Orange.

Geological summary

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: Semisopochnoi in May 2017. Credit: Max Kaufman, USGS/AVO


Severe flooding damages roads, hundreds of houses in northern Morocco

March 02, 2021

Heavy rains triggered severe flash flooding in the city of Tetouan in northern Morocco on Monday, March 1, 2021, leaving 275 houses damaged, as well as dozens of vehicles and infrastructure. The dramatic situation in Tetouan made rounds on social media. Roads and...

Deadly snowfall leaves 94 injured, hundreds of cars trapped in South Korea

March 02, 2021

One person was killed while 94 others sustained injuries as heavy snowfall engulfed South Korea's northeast region, authorities reported Tuesday, March 2, 2021. Hundreds of vehicles were trapped on some parts of a highway along the east coast, while more than...

Heavy snowfall engulfs many parts of Russia

February 26, 2021

Heavy snow has blanketed many parts of Russia in the past few days, cutting power to more than 30 000 people and leaving various regions and cities struggling to deal with the extreme weather. Thousands of people have been affected, with others having to dig their...

More than 7 700 households without water supply as record snow hits Hokkaido, Japan

February 26, 2021

Heavy snow has been falling intermittently in Hokkaido, Japan, since Tuesday, February 23, 2021, with Iwamizawa city recording its second-highest snowfall of 2.05 m (6.7 feet) on Thursday, 25. It resulted in disruptions in the city, particularly in train services...

6th impressive paroxysm at Etna volcano, Italy

February 25, 2021

This is the 6th paroxysmal eruptive episode at Etna volcano, Italy since February 16, 2021. After 5 impressive paroxysms, the activity at the volcano intensified again at 19:00 UTC on February 24 and evolved into another spectacular event. Video courtesy Gio Giusa...


Comments

No comments yet. Why don't you post the first comment?

Post a comment

Your name: *

Your email address: *

Comment text: *

The image that appears on your comment is your Gravatar