USGS triggers volcanic alert with explosion signals detected

View of the eastern cone of Mount Cerberus in the Semisopochnoi caldera. Image: USGS / AVO / CA Neal

Due to the low-level volcanic ash emissions and detection of explosion signals, scientists at the USGS Alaska Volcano Observatory (AVO) have improved the color coding and alert level of the Semisopochnoi volcano. The color code changed from YELLOW to ORANGE and the alert level changed from ADVISORY to WATCH.

According to the AVO, several small explosions were detected yesterday in regional infrasound data and a small ash cloud was observed on a satellite image from 3:21 p.m. (11:21 p.m. UTC) on May 17, prompting the team of scientists to raise both the color code. and alert level. AVO says sulfur dioxide emissions may have been detected in satellite data in the past 24 hours.

Small eruptions producing minor ash deposits near the active northern crater of Mount Cerberus and ash clouds less than 10,000 feet above sea level are typical of recent activity at Semisopochnoi.

The Sentinel-3 Earth observation satellite shows ash rising from the Semisopochnoi volcano.  Image: AVO
The Sentinel-3 Earth observation satellite shows ash rising from the Semisopochnoi volcano following an eruption in April. Image: AVO

Due to its location on the globe at 179 ° 46 ′ East, Semisopochnoi is the most easterly 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 other smaller islands. These islands, with their 57 volcanoes, form the northernmost part of the Pacific Ring of Fire.

The Ring of Fire is an area around the edge of the Pacific Ocean where numerous volcanic eruptions and earthquakes occur. Caused by plate tectonics, the lithospheric plates under and around the Pacific Ocean move, collide and / or are destroyed, creating the seismic activity for which the Ring of Fire is famous.

The volcanoes in this part of the Ring of Fire are monitored by the Alaska Volcanoes Observatory (AVO), which is a joint program of the US Geological Investigation (USGS), the Geophysical Institute of the University of Alaska at Fairbanks (UAFGI), and the Alaska State Geological and Geophysical Survey Division (ADGGS). AVO is similar to the Hawaii Volcanoes 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; while Semisopochnoi is now under WATCH, Cleveland is under NOTICE while Veniaminof has no assigned status.

Alaska is however home to many volcanoes; there are over 130 volcanoes and volcanic fields that have been active over the past two million geologically young years. 50 have been active since the mid-1700s and AVO is studying them as well. In the case of Semisopochnoi, the volcano is monitored by satellite data and lightning detection instruments. An infrasound array on Adak Island can detect explosive emissions from Semisopochnoi with a slight delay of about 13 minutes, weather permitting.

AVO is responsible for issuing aviation codes and alert levels for volcanic activity. Aviation codes are green, yellow, orange or red. When ground instrumentation is insufficient to establish that a volcano is at a typical background activity level, it is simply “unassigned.” While green signifies typical activity associated with a non-eruptive state, yellow signifies that a volcano is showing signs of elevated unrest above known background levels. When a volcano exhibits increased or intensifying unrest with the increased eruption potential, it turns orange. Finally, when an eruption is imminent with a significant emission of volcanic ash expected in the atmosphere or an eruption is in progress with a significant emission of volcanic ash in the atmosphere, the code turns red. Volcanic activity alert levels are normal, advisory, monitoring, or warning. As with aeronautical codes, if there is insufficient data, it is simply labeled as “unassigned”. When the volcano is at typical background activity in a non-eruptive state, this is considered normal. If the volcano shows signs of elevated unrest above background level, an advisory is issued. If a volcano is exhibiting increased unrest or escalation, a watch is issued while a warning is issued when a dangerous eruption is imminent.

Volcanic ash can create important damage to the jet engines passing through them or to the boat and car engines that ingest air filled with ash. Volcanic ash is hard and abrasive and can quickly cause significant wear and tear on various aircraft parts such as propellers, turbocharger vanes, and even cockpit windows. Because volcanic ash particles have a low melting point, they can melt in the combustion chamber of a jet engine, creating a ceramic or glass glaze that then sticks to turbine blades, fuel nozzles, and to the combustion chambers. A jet engine that ingests only a small amount of ash could suffer from complete engine failure. Overheating and engine failure are also possible in cars and trucks because volcanic ash can seep into almost any opening in a vehicle. Ash is also very abrasive; Ash trapped between the windshield and the wiper blades will scratch and permanently mark the windshield glass, and the windows are susceptible to scratching each time they are raised, lowered, and cleaned.

Volcanic ash from the Aleutians could be problematic for trans-Pacific planes traveling between Asia and North America.



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