The aviation color code and volcanic warning level of Mount Gareloi stratovolcano, the westernmost volcano in the United States, have been elevated by the USGS and its Alaska Volcano Observatory (AVO). AVO elevated the aviation color code to YELLOW and the Volcano Alert Level to advisory yesterday due to increased seismic activity at the volcano above background levels.

Gareloi Volcano
(Photo : Wikimedia Commons)

Rise in Seismic Activity

According to the AVO, Mount Gareloi saw a mild rise in seismic activity on May 18, and a persistent rise in the rate and size of minor volcanic earthquakes began on May 27. While seismic activity has risen, the AVO reports that satellite data and web camera images show no other significant changes at the volcano.

"Sulfur dioxide gas has been discovered in satellite photos from Gareloi during the last week, which is consistent with previous readings. An AVO field team flying above the summit on May 23 saw no activity," the AVO said in a statement.

The fumarole area in the south crater of the Gareloi volcano continues to release magmatic gases, and low-level seismic activity is regular. According to AVO, these findings point to shallow magma and the possibility of interaction with a hydrothermal system. "The present rise in seismicity is likely due to a shift in the magmatic-hydrothermal system, but the risk of a volcanic eruption has not increased."

Alaska Volcanic Activity

Gareloi Volcano
(Photo : Wikimedia Commons)

The Alaska Volcano Observatory, a collaborative operation of the United States Geological Survey (USGS), the University of Alaska Fairbanks Geophysical Institute (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS), monitors volcanoes in this part of the Ring of Fire. The Hawaii Volcano Observatory (HVO), which monitors Hawaii's three active volcanoes: Kilauea, Mauna Loa, and Hualalai, is identical to the AVO. They also keep an eye on Cleveland, Semisopochnoi, and Veniaminof in the case of AVO.

Alaska has many volcanoes; there are over 130 active volcanoes and volcanic fields in the last 2 million years. Since the mid-1700s, 50 have been active, and AVO investigates them as well.

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Alert Levels

Gareloi Volcano
(Photo : Wikimedia Commons)

Aviation Codes and Volcanic Activity Alert Levels are issued by the AVO. Green, yellow, orange, or red is the many types of aviation codes. When ground-based monitoring fails to show that a volcano is operating at an average background level of activity, it is simply designated as "unassigned."

Yellow indicates that a volcano displays high unrest symptoms above known background levels, whereas green indicates usual activity associated with a non-eruptive condition.

When a volcano shows increasing or growing unrest with an elevated risk of eruption, the color changes to orange. Finally, the code becomes red when an eruption is imminent, with large volcanic ash emissions predicted in the atmosphere or when an eruption is underway. Large volcanic ash emissions are predicted in the atmosphere. The activity of Volcanoes Normal, advisory, watch, or warning alert levels are available.

If data is lacking, it is simply classified as "unassigned," as with aviation codes. It is deemed normal when the volcano is operating at normal background levels in a non-eruptive condition.

An advisory is issued if the volcano shows evidence of heightened disturbance above the background level. A watch is issued when a volcano shows signs of increased or growing disturbance, whereas a warning is issued when a dangerous eruption is imminent.

Local Seismic Network

A local seismic and infrasound network, satellite data, and regional infrasound and lightning-detection networks all keep an eye on Gareloi. In addition, AVO says they'll keep an eye on things to see if the latest changes are due to a fresh intake of magma or other changes in the magma system. If an eruption looks to be impending, the aviation and alarm codes will be raised correspondingly.

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