Friday, April 26, 2013

Cleveland covered in clouds

Cleveland is the most active volcano of the Aleutian island arc and appears as a typical stratovolcano with its nearly symmetrical shape (symmetry being quite typical for Alaskan volcanoes in general). The 1730 m high volcano is located on the western portion of the uninhabited Chuginadak Island (Aleut name: Tanax̂ Angunax̂) which is also the native Aleut name of the volcano. Chuginadak is the Aleut goddess of fire who is believed to reside in the volcano. Interestingly, the name refers to the volcano’s constant activity throughout time. The name Cleveland was given to the volcano in 1894 after the then-president of the United States Grover Cleveland.

Chuginadak is part of an island chain called Islands of Four Mountains. The name derived from the Russian Четырехсопочные Острова (Ostrava Chetyre Soposhnye) which was given to the chain by Russian explorers that noticed four prominent mountains in 1826. The Islands of Four Mountains also include Amukta, Chagulak (a 3km wide island with a steep 1142m high volcano), Yunaska (the largest island), Herbert (a circular island with a 2km wide caldera), Carlisle (containing a 1610m high stratovolcano), Uliaga (the northernmost and smallest which in the 80s was ravaged by a shipwreck leaking oil) and the Kagamil Islands. Thus, it appears there are more than four mountains, although Cleveland, Chagulak, Herbert and Carlisle were probably the most ‘prominent’. These volcanoes have an unknown eruptive history.

The eastern part of Chuginadak Island, which contains the heavily eroded Tana volcanic complex, is connected to Cleveland volcano by a narrow isthmus. Aleut oral history mentions that Cleveland and the eastern part of Chuginadak Island were separate islands in the past.

Since 1893, Cleveland had approximately 15 eruptions which are characterized by explosive ash emission (eruption columns can be up to 12 km high), lava flows and lava fountaining. VEI (Volcanic Explosivity Index: see 3 eruptions occurred in 1944, 1987, 1994 and 2006. However, it is difficult to monitor the volcano because of its isolated location. Nowadays a webcam located on the closest inhabited island, Umnak Island keeps a close eye on the volcano. In addition, the volcano is monitored by satellite imagery. Unfortunately, due to the typical bad weather in the area the island is invisible half of the time. Another aspect is that the volcano is not seismically monitored. Thus, eruptions could still go unnoticed.

From the end of January until the beginning of February 2013 a lava dome in the crater grew to a diameter of 200m. Since then, the few clear days that have occurred did not show any changes of growth of the summit dome. Currently, Cleveland is under volcano alert level yellow (see more information on volcano alert color codes see: implying that unrest is occurring but there is no eminent eruption, well at least not yet.

Image: Cyrus Read (USGS). The image shows Cleveland volcano in the back with Carlisle volcano on the foreground.

References and further reading

Webcam monitoring Cleveland from the Alaska Volcano Observatory:

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