Cleveland, at the western end of the isolated Chuginadak Island in the Aleutian Islands, is characterized by frequent small explosions that are monitored using local seismic and infrasound sensors, and by elevated surface temperatures that are monitored by satellite-based infrared sensors. The current eruptive period began in April 2016 and has continued through at least July 2018. The Alaska Volcano Observatory (AVO) is responsible for monitoring, and issues regular reports describing activity.

Small explosions in mid-December 2017 were followed by elevated surface temperatures later in the month and a lava flow in the summit crater that began effusing on 5 January 2018 (table 9). Thermal anomalies and other signs of unrest continued through 24 February, when a small explosion was detected. Another explosion was reported on 2 March with a plume rising to 4.6 km altitude and drifting ENE. Satellite data continued to identify elevated temperatures in early March. Small explosions were identified using seismic and infrasound data on 14 March and 4 April. The ash cloud on 4 April rose to 4.6 km altitude and drifted SW; hot material was ejected onto the W flank.

Thermal anomalies were ongoing in June. A small circular lava flow (~80 m in diameter) in the summit crater was reported on 25 June; a thermal anomaly noted during 29 June-2 July extending SW downslope within the crater was consistent with a lava flow, according to AVO. Weakly elevated surface temperatures were reported on many days during 7-23 July, along with some small steam plumes (figure 25). A small deposit of blocks, within the summit crater and just below the E crater rim, seen using satellite imagery during 18-23 July suggested to AVO that there had been a very small explosion not recorded using seismic or pressure sensor monitors.

Table 9. Observations of dome growth and other crater activity at Cleveland, December 2017-July 2018. Note that the absence of observable activity from satellites is often due to cloud cover. Data courtesy of Alaska Volcano Observatory (AVO).

Figure 25. Worldwide-3 satellite image of the summit crater of Cleveland volcano on 10 July 2018. The 80-m-diameter circular lava flow extruded in late June 2018 can be seen as well as minor steam emissions. Courtesy of Alaska Volcano Observatory / U.S. Geological Survey (Image 117311, color adjusted).

Geological Summary. The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 it produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845 USA (URL: http://vaac.arh.noaa.gov/).