Tag Archives: AVO

1 March 2023

Getting Edgy Under Edgecumbe

By icefogger
Mount Edgecumbe, as seen from Thomsen Harbor, Sitka, Alaska; Photo credit:U.S. Forest Service/Jeffrey Wickett

Last April, a series of earthquakes around and under Mount Edgecumbe brought greater attention to what was considered a dormant volcano. Measurements show that magma is moving deep underneath Edgecumbe. Other signs have also brought new scrutiny: Hikers have discovered vents with bubbling gas near the volcano, and satellite images show a bulging of the ground around Edgecumbe.

None of this means that Edgecumbe will blow anytime soon, but the State of Alaska has reclassified Mount Edgecumbe as a “high risk volcano”. With 73,000 people living in the region, the reclassification was probably wise. Currently, the east side of Edgecumbe is bulging faster than any volcano in Alaska.

The Alaska Volcano Observatory has plans to install seismic sensors and other instruments on Mount Edgecumbe over the coming months. Core samples show that the volcano erupted between 4000 -4300 years ago, and Tlingit oral history tells of an eruption approximately 800 years ago.

Currently, Alaska has one volcano at Code Orange, and four others at Code Yellow.

Unrest under Mount Edgecumbe and a bulging eastern flank

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12 February 2023

Alaska helped take down the Roman Republic

By icefogger

Volcano Week:

Okmok Volcano; Image credit AVO

Ice core records from the Arctic show that Alaska’s Okmok Volcano had a massive eruption in 43 BCE. Following the eruption, there was an abrupt cooling globally, which led to crop failures, famine, disease, and eventually, social unrest. The Mediterranean region was no exception to this.

Such a shift in climate, coming a year after the assassination of Caesar, would have put great pressure on local powers. Strain was also felt in Egypt.

Okmok has a very active history. At one time, it had a 150 meter deep lake in its crater. A notch in the rim eventually drained the lake, although some small remnant lakes remain near cones B & D.

The eruptions of Okmok 8300 and 2050 years ago earn a Volcanic Explosivity Index rating of 6, which puts it on par with Novarupta and Krakatoa.

On 12 July 2008, Okmok erupted without warning, sending ash 50,000 feet into the air. It erupted continuously for almost six full days, causing transportation problems in the air and on the water for the region. That eruption was ranked a 4 VEI, which is considered “cataclysmic”.

Okmok Volcano; Photo credit: AVO/Burke Mees

Back to 43 BCE. The decade following the eruption was one of the coldest in a millennia, with 43 and 42 BCE being some of the coldest years. It is believed that a temperature drop of 7C from normal was a result of the volcanic eruption on the other side of the globe.

The full, scientific report can be found here:

https://www.pnas.org/doi/full/10.1073/pnas.2002722117

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22 August 2022

North Cerebus

By icefogger

Semisopochnoi goes Orange; Photo credit Matt Loewen

The North Cerebus crater at Semisopochnoi Island released a large ash plume on Sunday. It was the first confirmed emission since June 12.

Semisopochnoi has no native land mammals, but it is home to over 1 million sea birds.

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28 April 2022

Magma Rising

By icefogger
Mount Edgecumbe displacement; Graphic credit: AVO

A couple of weeks ago, I posted about the swarm of earthquakes underneath Mount Edgecumbe. The numbers are in, and radar satellite data reveals a ground deformation around the volcano. Data was analyzed for the past 7.5 years, and since 2018, an uplift around Mt Edgecumbe has been constant. The peak activity, around the crater, has shown an average uplift of 3.4″ per year since 2018, and a total uplift of 10.6″.

Earthquakes in and around Mt Edgecumbe, Map credit: AVO

With the data of the ground deformation, AVO has come to the conclusion that the swarm of earthquakes is due to the movement of magma below Mount Edgecumbe, and not due to tectonic activity.

Mount Edgecumbe, a 3200 foot high stratovolcano, lies 15 miles to the west of the community of Sitka. There is no volcanic monitoring system on Edgecumbe, but there is at Sitka. AVO plans to install instruments closer to the volcano in the near future.

The rising of magma under a volcano does not necessarily mean that an eruption is imminent. The deformation and earthquakes could cease at any time. If an eruption were to occur, warning signs such as increased rate of deformation, and an increase in the earthquake swarms, would give advance warning of an eruption.

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8 February 2022

Pavlof from space

By icefogger
Image credit: AVO/HannahDietterich on January 19, 2022

Pavlof is one of three volcanos in Alaska at Level Orange. Orange means that the volcano is experiencing unrest, and may be experiencing an eruption with little to no ash emissions.

We have one volcano at Level Yellow, which is at an elevated unrest. It this particular case, Davidof volcano has experienced a swarm of earthquakes in the past 24 hours.

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26 August 2021

Atka Volcanic Complex

By icefogger
Earthquake activity on Atka Island

The southern portion of Atka Island is older than the north, with some volcanic rock dating back 5 million years. The active northern part of the island once had one large cone, which was lost in a large eruption, and is now peppered with several smaller volcanos.

A volcanic complex can have several vents, and a widely varying composition of lava. Seismic activity within a complex can be difficult to pinpoint the source of the activity. Which vent is rumbling now? Some of those smaller vents have developed into stratovolcanoes.

Korovin Volcano has been very active in recent times, while Mount Kliuchef last erupted in 1812. The Atka Complex recently was elevated to a Level Yellow, due to seismic activity on the island. Interestingly, the swarm of activity is not near the known suspects, but several kilometers the the west and southwest, and approximately 10 miles from the community of Atka.

Source: AVO

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11 August 2021

Great Sitkin & other rumblings

By icefogger
The growing lava dome on Great Sitkin; Photo credit: AVO/Dave Ward (8/4/21)

I had to share this shot from the Alaska Volcano Observatory and photographer Dave Ward. Great Sitkin has been at Level Orange and the lava dome has been growing since mid-July. According to AVO, the dome is now 100 meters across. What are the odds of having such a clear day out on Great Sitkin Island? Wonderful shot by Mr Ward.

Great Sitkin has been active most of the summer, although that lava dome build up has occurred in the last couple of weeks.

The glow of Great Sitkin at night. Photo credit: AVO/Peggy Kruse

Both Pavlof and Semisopochnoi Volcanos are also at Level Orange. Pavlof is known to erupt with little to no warning, and it is showing elevated seismic activity, and at least one ash eruption. Explosions and elevated seismic activity on Semisopochnoi Island also continues. At least one ash eruption dissipated quickly, and sulfur dioxide emissions have been detected by satellite.

Cleveland Volcano rounds things out at a Level Yellow. Some seismic activity, but no reported ash eruptions.

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2 June 2021

Timing is everything

By icefogger
An eruption plume from the Great Sitkin volcano on the Aleutian Chain

Volcanos world-wide seem to be getting a bit anxious of late, and Alaska has three rumbling right now. The Great Sitkin volcano, which dominates the skyline of Great Sitkin Island, erupted on May 25. Lauren Flynn of the U.S. Fish & Wildlife Service captured this image as Great Sitkin erupted. Flynn was aboard the Research Vessel Tiglax at the time.

Great Sitkin Island was a fuel depot during WWII. The island lies between Adak and Atka, and is roughly 11 miles long by 10-1/2 miles wide. The Great Sitkin volcano rises to a height of 5710 feet above sea level.

Photo credit: Lauren Flynn/USF&WS/AVO

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9 March 2021

Veniaminof goes Orange

By icefogger
Mount Veniaminof; Photo credit: AVO/Allan Lerner

Mount Veniaminof, which is located on the Alaska Peninsula, erupted last Thursday. The ash plume that exploded from the volcano did not reach 10,000 feet. Veniaminof last erupted in the fall of 2018.

Mount Veniaminof is a rather active stratovolcano, having erupted at least 14 times in the past 200 years. It is surrounded by a 25 square mile ice field. According to the National Park Service, the glacier is the only one known in North America with an active volcano at its center.

Image credit: AVO/Hannah Dietterich

As of 7 March, Veniaminof continued to show an ash plume via satellite imagery. Mount Veniaminof rarely shows itself for the camera. The volcano is visible only one or two days a year, the rest of the time, Veniaminof is shrouded in clouds and fog.

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19 December 2018

Mount Veniaminof

By icefogger


Mount Veniaminof letting off some steam, 25 September 2018; Photo credit: AVO/Mari Peterson

Mount Veniaminof, the glacier covered volcano on the Alaska Peninsula, has been erupting since early September. The Alaska Volcano Observatory reports that lava is still flowing from the caldera this week. The volcano last erupted in 2013.


ESA Sentinel-2 image of Veniaminof, showing lava flow on the south flank of the volcano. Photo credit: AVO/USGS

Veniaminof sent a plume of ash, 13,000′ into the air in late November, but that action has come to a stop, at least for now.

Currently joining Veniaminof on AVO’s Orange Alert List, is the seemingly always active Mount Cleveland.

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