A large, potentially dangerous volcano isn’t erupting yet, but scientists say odds have increased of eruptive activity at the Cleveland Volcano. This large stratovolcano, located in the Islands of Four Mountains group of the Aleutian chain in Alaska, is 5,676 feet tall and nearly perfectly symmetrical. One of the most active volcanoes in the Aleutian Arc, Cleveland has erupted at least 22 times in the last 230 years. Most recently Mount Cleveland has erupted three times in 2009, twice in 2010, once in 2011 and in 2016 and 2017. A small eruption occured on June 2 last year.
The volcano is monitored by the Alaska Volcano Observatory (AVO), which is a joint program of the U.S. Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). The AVO is similar to the Hawaii Volcano Observatory (HVO) which monitors Hawaii’s three active volcanoes: Kilauea, Mauna Loa, and Hualalai. In the case of AVO, they monitor Cleveland, Semisopochnoi, and Veniaminof, all of which are under watch or advisory now. 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.
According to AVO, satellite detections of increased volcanic gas emissions and elevated surface temperatures were observed at Cleveland Volcano beginning on March 17. In addition, a local earthquake occurred on March 10 and it was large enough to be measured on seismometers 100 km away on Umnak Island. AVO cautions, “These data indicate a potential for increased eruptive activity at Cleveland.” Because of that threat, AVO raised the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY.
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 like the one now in effect for Cleveland 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.
Explosions from Cleveland typically produce relatively small volcanic ash clouds that dissipate within hours; however, more significant 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 the more flat shield volcanoes found in Hawaii, in a stratovolcano like Cleveland, the lava builds up around the vent forming a volcano with steep sides. Stratovolcanoes are more likely to produce explosive eruptions due to gas building up in the viscous magma inside
If Cleveland erupts, it’ll join a busy stage of other active volcanoes around the globe. Mt. Etna in Italy has been quite active since February. There, typical lava fountains reaching 1,500 metres (4,921 feet) have been lighting up the night sky for miles around while hazardous rock and ash continues to land in nearby communities. A larger eruption could happen there soon too. In Iceland, a new volcano was born on the southwest portion of the island nation. There, lava is flowing away from populated areas near Iceland’s capital city. In Hawaii, activity is up at the world’s largest volcano, Mauna Loa, prompting the HVO to encourage people develop a communication plan and prepare a “go bag” should it blow soon.
