The USGS reports “high” activity on 7 different volcanoes around the United States that it observes, with three at increased ORANGE / WATCH and four at YELLOW / ADVISORY.
The Volcanoes Hazards Program Office, through the regional groups responsible for volcanoes of concern in their geographic area of concern, 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 “unaffected”. 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 increasing unrest with 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 aviation 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, it is considered normal. If the volcano shows signs of elevated unrest above background level, an advisory is issued. If a volcano is exhibiting increased or increasing unrest, a watch is issued while a warning is issued when a dangerous eruption is imminent.
At the time of this article’s publication, Semisopochnoi, Great Sitkin and Pavlof volcanoes are all at ORANGE / WATCH while Cleveland, Pagan, Mauna Loa and Kilauea are all at YELLOW / ADVISORY.
Semisopochnoi, Great Sitkin, Cleveland and Pavlof volcanoes are all located in Alaska while Mauna Loa and Kilauea are in Hawaii. The Pagan volcano is located in the northern Mariana Islands, north of Guam.
Based on 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 to the west of the 180th meridian of 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.
Semisopochnoi saw explosive activity earlier this week, prompting the Alaska Volcano Observatory (AVO) to upgrade the concern there to RED / WARNING. As the unrest continues there, there are only discreet, low-level ash explosions, resulting in a drop to ORANGE / WATCH.
Great Sitkin is at a high ORANGE / WATCH level due to ongoing unrest and high surface temperatures seen in satellite data.
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 is located approximately 26 miles east of Adak, 1,192 miles southwest of Anchorage. According to AVO, the volcano has a composite structure consisting of an older dissected volcano and a younger parasitic cone with a crater at the top 1.8 miles in diameter. A steep-sided lava dome, set up during an eruption in 1974, occupies the center of the crater. Over the past 280 years, a large explosive eruption has produced pyroclastic flows here that partially filled the Glacier Creek valley on the southwest flank.
Pavlof Volcano is a stratovolcano located at the southwestern end of the Alaska Peninsula, just under 600 miles southwest of Anchorage. The volcano is approximately 4.4 miles in diameter and has active vents on the north sides and is near the summit. According to the USGS, the volcano has experienced more than 40 historical eruptions, making it one of the most active volcanoes in the Aleutian Arc. The Aleutian Arc is located on 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.
According to AVO, “unrest continues” at Pavlof, with an “explosive event detected” on both webcam and seismic data. This volcano has been at this high alert level since early August.
The USGS Northern Mariana Islands office (NMI) tracks the activity of the Mount Pagan Pagan Island volcano. Unfortunately, data is very limited on this volcano. Bad weather and years without repairs have left geologists there almost blind to what is happening on the surface. In the latest July NMI update, they report: “Ground-based geophysical monitoring data from stations on Anatahan and Sarigan Islands has not been available since the storm damage in August 2017. The current logistical challenges of the CNMI prevent visiting these sites to make repairs. The timetable for returning these stations to service is uncertain. “
Although there is limited observation equipment at the surface, the NMI reports that satellite photography has not revealed any recent volcanic activity. While some volcanic activity was reported by locals earlier this month, activity appears to have ceased for now.
A large, potentially dangerous volcano is not yet erupting, but scientists say the odds of eruptive activity have increased at Cleveland Volcano. This large stratovolcano, located in the Four Mountain Islands group of the Aleutian chain in Alaska, is 5,676 feet tall and is almost perfectly symmetrical. One of the Aleutian Arc’s most active volcanoes, Cleveland has erupted at least 22 times in the past 230 years. Most recently, Mount Cleveland erupted three times in 2009, twice in 2010, once in 2011, and in 2016 and 2017. A small eruption occurred on June 2 of last year.
While AVO reports that no unusual activity has been observed in satellite or seismic data, unrest continues at Cleveland Volcano.
The Hawaii Volcanoes Observatory (HVO) monitors Kilauea, Mauna Loa, and Hualalai volcanoes on the Big Island of Hawaii. Mauna Loa is considered the largest active volcano in the world. None of Hawaii’s volcanoes are currently erupting, but seismicity remains above background levels in both Kilauea and Mauna Loa.
Although there is activity and unrest on the volcanoes of Alaska, Hawaii, and the Northern Mariana Islands, no volcano in the Americas shows signs of unrest or activity at the time of the outbreak. publication of this article.