A volcano that has been exhibiting off-again, on-again seismic activity this year is exhibiting significant unrest once again, forcing scientists with USGS and the Alaska Volcano Observatory (AVO) to raise the volcano alert level of the Semisopochnoi Volcano. According to the AVO, “Detection of multiple, discrete, energetic explosion signals on local seismic and infrasound stations has characterized the unrest over the past day.” It also appears an explosion occurred last night and more may be on the way.
AVO reports: “Last night at about 10:15 PM AKDT (06:15 UTC, 8/3/2021) an explosion and an intense burst of seismic and acoustic tremor lasting for roughly 15 minutes was detected on the local network. This activity produced a small ash cloud that was visible in satellite data until about 9:20 UTC (01:20 AKDT).”
Based on its location on the globe at 179°46′ East, Semisopochnoi is the easternmost land location in the United States and North America, located just 9.7 miles west of the 180th Meridian in Alaska. Semisopochnoi is part of the Aleutian Islands, a chain of 14 large volcanic islands and 55 smaller other islands. These islands, with their 57 volcanoes, make the northernmost part of the Pacific Ring of Fire.
The Ring of Fire is a region around the rim of the Pacific Ocean where many volcanic eruptions and earthquakes occur. Caused by plate tectonics, lithospheric plates under and around the Pacific Ocean move, collide, and/or are destroyed, creating the seismic activity the Ring of Fire is famous for.
Volcanoes in this portion of the Ring of Fire are monitored by the Alaska Volcano Observatory (AVO), which is a joint program of the U.S. Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). The AVO is similar to the Hawaii Volcano Observatory (HVO) which monitors Hawaii’s three active volcanoes: Kilauea, Mauna Loa, and Hualalai. In the case of AVO, they monitor Cleveland, Semisopochnoi, and Veniaminof too. Alaska is home to many volcanoes, though; there are more than 130 volcanoes and volcanic fields which have been active within the geologically young last 2 million years. 50 have been active since the mid 1700s and AVO studies those too.
AVO is responsible for issuing Aviation Codes and Volcanic Activity Alert Levels. Aviation Codes are green, yellow, orange, or red. When ground-based instrumentation is insufficient to establish that a volcano is at a typical background level of activity, it is simply “unassigned.” While green means typical activity associated with a non-eruptive state, yellow means a volcano is exhibiting signs of elevated unrest above known background levels. When a volcano exhibits heightened or escalating unrest with the increased potential of eruption, it jumps to orange. Finally, when an eruption is imminent with significant emission of volcanic ash expected in the atmosphere or an eruption is underway with significant emission of volcanic ash into the atmosphere, the code becomes red. Volcanic Activity Alert levels are normal, advisory, watch, or warning. As with aviation codes, if data is insufficient, it is simply labeled as “unassigned.” When the volcano is at typical background activity in a non-eruptive state, it is considered normal. If the volcano exhibits signs of elevated unrest above background level, an advisory is issued. If a volcano exhibits heightened or escalating unrest, a watch is issued while a warning is issued when a hazardous eruption is imminent.
For now, the AVO is keeping the code / alert level to “ORANGE / WATCH” for Semisopochnoi.
The AVO says additional explosions and ash plumes are possible, which could be problematic for trans-Pacific Jets that fly near the volcano on their Asia – North America routes. Volcanic ash can create significant harm to jet engines that fly through them or boat and automobile engines that ingest ash-filled air. Volcanic ash is hard and abrasive, and can quickly cause significant wear to various airplane parts such as propellers, turbo-compressor blades, and even cockpit windows. Because volcanic ash particles have a low melting point, it can melt in the combustion chamber of a jet engine, creating a ceramic or glass-like glaze that then sticks to turbine blades, fuel nozzles, and combustors. A jet engine that ingests just a small amount of ash could suffer from total engine failure. Overheating and engine failure is also possible in cars and trucks since volcanic ash can infiltrate nearly every opening in a vehicle. Ash is also very abrasive; ash caught between windshields and wiper blades will scratch and permanently mark the windshield glass, and windows are susceptible to scratching each time they are raised, lowered, and cleaned.
According to AVO, small eruptions producing minor ash deposits within the vicinity of the active north crater of Mount Cerberus and ash clouds under 10,000 ft above sea level are typical of recent activity at Semisopochnoi. If ash remains at or below this altitude, trans-Pacific aviation won’t be impacted. But if a larger eruption ejects matter higher into the atmosphere, it could create problems for aviators.
Semisopochnoi is monitored by local seismic and infrasound sensors, satellite data, regional infrasound, and lightning detection instruments.
Semisopochnoi is the second volcano in Alaska to be at an elevated ORANGE / WATCH level in recent weeks. On July 23, USGS elevated the alert level and color code to ORANGE / WATCH for the Great Sitkin Volcano.
Alaska also saw an impressive 8.2 earthquake on July 29, which prompted the issuance of many tsunami warnings and watches. Scientists are concerned that any explosive eruption at any of the volcanoes in the state could trigger an earthquake and/or tsunami threat for Alaska and beyond.