The USGS has detected a significant increase in seismic activity at the Aniakchak Volcano, prompting them to raise the alert level for possible volcanic activity there. USGS’s Alaska Volcano Observatory (AVO) issued a volcanic activity notice saying that the number of earthquakes has recently increased and shifted to shallower depths. Due to this increased activity to above-background levels, the AVO raised the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. While volcanic activity is possible, USGS does not believe an eruption is imminent.
In the U.S., the USGS and volcano observatory units are 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.
USGS says beyond this seismic activity, there have been no signs of unrest in other monitoring data. AVO wrote in their volcanic activity notice, “There is no indication that an eruption of Aniakchak is imminent, or that one will occur. Increases in seismic activity have been detected previously at other similar volcanoes, with no subsequent eruptions. We expect additional shallow seismicity and other signs of unrest, such as gas emissions, elevated surface temperatures, and surface deformation to precede any future eruption, if one were to occur.”
According to AVO, background seismicity at Aniakchak has mostly been characterized by deep, long-period events occurring at a rate of ~4 earthquakes per month. From October 2022 to present, the rate of earthquakes has been more elevated and characterized by shallower earthquakes. The earthquake rate has further increased since January 31 with dozens of earthquakes detected per day, including a magnitude 3.7 earthquake on February 17.
Within the United States, the USGS tracks 169 potentially active volcanoes, most of which are in Alaska. 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. Another place famous for its volcanoes is Hawaii; on the Big Island of Hawaii, Kilauea, Mauna Loa, and Hualalai are considered active and potential threats, however only one is erupting today: Kilauea. The U.S. is only home to a fraction of the world’s volcanoes: according to USGS, there are normally around 2 dozen erupting volcanoes around the world at any given time. The USGS says there are about 1,500 potentially active volcanoes worldwide, with about 500 of the 1,500 erupting in modern historical times.
Other USGS units monitor volcanoes around the country. The Hawaii volcanoes are monitored by the Hawaii Volcano Observatory (HVO). In addition to the AVO and HVO, there are also the California Volcano Observatory , Cascades Volcano Observatory, the Yellowstone Volcano Observatory, and the Northern Mariana Islands Volcano Observatory. Each of those additional volcano observatories within the USGS are monitoring volcanoes in their respective regions. At this time, none of those other observatories are reporting unusual activity or signs of anything more than background noise for now.
Aniakchak Volcano is located within the Aniakchak National Monument and Preserve which is maintained by the National Park Service. In 1967, the volcanic caldera located here was designated as a National Natural Landmark by the National Park Service. The volcano is roughly 3,700 years old and has a caldera that is roughly 6 miles in diameter. The volcano is classified as a stratovolcano.