A large, potentially dangerous volcano is yet to erupt, but scientists say the chances of eruptive activity at Cleveland Volcano have increased. USGS scientists monitoring it have raised the volcano’s alert level and aviation color code to ADVISORY/YELLOW due to elevated surface temperatures and increased sulfur dioxide emissions.
This large stratovolcano, located in the Island Group of Four Mountains in Alaska’s Aleutian Range, is 5,676 feet tall and almost perfectly symmetrical. One of the most active volcanoes in the Aleutian Arc, Cleveland has erupted at least 22 times in the past 230 years. More 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, 2020.
The volcano is monitored by the Alaska Volcano Observatory (AVO), which is a joint program of the US Geological Survey (USGS), the University of Alaska Fairbanks Geophysical Institute (UAFGI), and of the Geological and Geophysical Division of the State of Alaska. Surveys (ADGGS). AVO is similar to the Hawaii Volcano Observatory (HVO) which monitors Hawaii’s three active volcanoes: Kilauea, Mauna Loa and Hualalai. In AVO’s case, they’re watching Cleveland, Semisopochnoi and Veniaminof, all of which are under watch or advisory now. Alaska is home to many volcanoes, however; there are over 130 volcanoes and volcanic fields that have been active in the past 2 million geologically young years. 50 have been active since the mid-1700s and AVO is also studying them.
According to AVO, satellite detections of increased volcanic gas emissions and elevated surface temperatures were observed at Cleveland Volcano beginning May 10. AVO warns: “Episodes of lava outpouring and explosions may occur without prior warning. Cleveland explosions are normally short-lived and only pose a hazard to aviation in the immediate vicinity of the volcano. Larger explosions that present a more widespread hazard to aviation are possible, but are less likely and occur less frequently.
Aviation codes are green, yellow, orange or red. When there is insufficient ground instrumentation to establish that a volcano is at a typical background level of activity, 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 shows increased or increasing unrest with increased potential for eruption, 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, watch or warning. As with aviation codes, if the 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 shows signs of elevated unrest above background, an advisory like the one currently in effect for Cleveland is issued. If a volcano exhibits increased or increasing unrest, a watch is issued while a warning is issued when a dangerous eruption is imminent.
Cleveland explosions typically produce relatively small volcanic ash clouds that dissipate within hours; however, larger ash emissions are possible, especially if the stratovolcano experiences a full eruption. Stratovolcanoes have relatively steep sides and are more cone-shaped than shield volcanoes. Unlike flatter shield volcanoes found in Hawaii, in a stratovolcano like Cleveland, lava accumulates around the vent forming a steep-sided volcano. Stratovolcanoes are more likely to produce explosive eruptions due to the buildup of gas in the viscous magma inside