Weatherboy: The USGS continues to monitor volcanoes around the United States; of the more than 160 they watch, 7 are experiencing elevated activity. Due to that activity, two of them are at an elevated WATCH / ORANGE status while five are at an ADVISORY / YELLOW level All of the other volcanoes USGS is monitoring today are either at GREEN or unrated conditions.
The seven volcanoes showing signs of unrest or activity are the Great Sitkin volcano, Semisopochnoi, Kilauea, Aniakchak, Takawangha, Tanaga, and Trident. The two volcanoes earning the elevated WATCH/ORANGE status are Alaska’s Great Sitkin and Semisopochnoi volcanoes.
Within the United States, the USGS tracks dozens of potentially active volcanoes, most of which are in Alaska. In Alaska alone, 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. As of today, none are erupting but that could change in the coming days with signs of increased activity at Kilauea, the most active of the Hawaiian bunch. 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.
The Hawaii volcanoes are monitored by the Hawaii Volcano Observatory (HVO) while the Alaska volcanoes are monitored by the Alaska Volcano Observatory (AVO.) 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.
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.
The Great Sitkin Volcano is a basaltic andesite volcano that occupies most of the northern half of Great Sitkin Island, a member of the Andreanof Islands group in the central Aleutian Islands. It’s located roughly 26 miles east of Adak, which is 1,192 miles southwest of Anchorage. According to the AVO, the volcano has a composite structure consisting of an older dissected volcano and a younger parasitic cone with a 1.8 mile diameter summit crater. A steep-sided lava dome, emplaced during an eruption in 1974, occupies the center of the crater. Within the past 280 years, a large explosive eruption here produced pyroclastic flows that partially filled the Glacier Creek valley on the southwest flank.
According to AVO, a slow eruption of lava is likely continuing at the volcano, producing a thick lava flow within the summit crater. “An eruption of lava began at Great Sitkin Volcano in July 2021 and has continued to slowly erupt since, but no explosive events have occurred,” wrote AVO in today’s daily update.
View of the eastern cone of Mount Cerberus in the Semisopochnoi caldera. Image: USGS / AVO / C. A. NealBased 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. Semisopochnoi is monitored by local seismic and infrasound sensors, satellite data, regional infrasound, and lightning detection instruments.
According to the AVO, “There was no evidence of explosive activity in the geophysics data over the past day. Clouds obscured satellite and webcam views of Mount Young on Semisopochnoi Island and no activity could be observed. Periods of volcanic tremor was observed over the past day, as has been typical of recent activity.” However, USGS adds caution: “Small explosions and associated ash emissions may continue and could be difficult to detect, especially when thick cloud cover obscures the volcano.”
Mount Takawangha is a stratovolcano located in Tanaga Island, Alaska. It sits in close proximity with another volcano known as Mount Tanaga, which shares the same name as the island itself. Older and more eroded volcanoes can also be found east of Takawangha. According to AVO, there’s been elevated earthquake activity beneath Takawangha and nearby Tanaga Volcano over the last 24 hours. “We expect additional shallow seismicity and possibly other signs of unrest, such as gas emissions, elevated surface temperatures, and additional surface deformation to precede any future eruption, if one were to occur,” AVO wrote in today’s update report. For now, Takawangha is at a Yellow aviation color code level and an Advisory volcano alert level.
The Trident Volcano is on the Alaska Peninsula inside of the Katmai National Park. There are 23 domes that make up the complex stratovolcano, with the greatest elevation at 6,115 feet. According to USGS, the volcano earned its name from Robert Fiske Griggs of the National Geographic Society; he named it because of the three major peaks he saw there in 1916, similar to the three prongs of a trident fork.
Today, AVO released an update on Trident: “Over the past two days, there has been a slight increase in the number of shallow earthquakes near Trident. Variation in the rate of earthquake activity is common during periods of unrest, and we will continue to watch for additional signs of change in the monitoring data streams. No other activity was observed in mostly cloudy satellite and webcam data.” The current period of seismic unrest began on August 24, 2022.
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.
In today’s volcano update, AVO wrote, “Earthquake activity beneath Aniakchak volcano continued over the past day. Satellite and web camera images were mostly obscured by clouds over the past day. The current period of seismic unrest began in October 2022. 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 additional surface deformation to precede any future eruption, if one were to occur.”
On the Big Island of Hawaii, the Kilauea volcano is not erupting, and no active lava has been observed since March 7, 2023. However, slow, steady inflation in the summit region continues, while summit seismicity remains elevated. No significant changes have been observed along either of the volcano’s rift zones over the past day.
HVO/USGS urges visitors of Hawaii Volcano National Park and Kilauea Volcano there to exercise extreme caution at all times. “Other significant hazards also remain aroundKīlauea caldera from Halemaʻumaʻu crater wall instability, ground cracking, and rockfalls that can be enhanced by earthquakes within the area closed to the public. This underscores the extremely hazardous nature of the rim surrounding Halemaʻumaʻu crater, an area that has been closed to the public since early 2008.”
In today’s update from HVO, they described the activity at Kilauea which is currently at Yellow / Advisory status. “Slow, steady inflation continues; the recent uptick in inflation was short-lived and amounted to less than at microradian. Overall, inflation at the summit of Kilauea is higher than conditions preceding the January 5, 2023 summit eruption. Small flurries of earthquakes continue irregularly beneath Halemaʻumaʻu, Keanakākoʻi Crater, and the southern margin of Kaluapele (Kīlauea caldera) since April 16. Rates of summit earthquakes remain elevated, and additional earthquake flurries are possible. The most recent sulfur dioxide (SO2) emission rate of approximately 135 tonnes per day was measured on May 3.”
While Kilauea isn’t erupting now, the increased activity, which prompted the Yellow/Advisory status, could be indicative of something brewing at the volcano. Scientists at USGS and HVO will continue to monitor the activity; in addition to providing daily updates on its status, they will issue a special bulletin should signs of an eruption become apparent.
“You will see the accidents that are befalling us in our world, those that are on the cars, and the games, and that are on the water, and the flame and the fire, and the blood, and the volcanoes, and all these things. They are perishing. Why? The Spirit of God is being withdrawn from the earth.” Letters and Manuscripts, Volume 17, Ms 229, 1902, par. 28.