AVO reported that at 0817 on 21 July an explosion at Cleveland was detected in both infrasound and seismic data. Cloud cover up to 9.1 km (30,000 ft) a.s.l. obscured views; no ash above the cloud deck was observed. Observers on a boat at the NE side of Cleveland reported seeing a dusting of ash on the snow near the summit as well as moderate steaming from the summit area. The Aviation Color Code was raised to Orange and the Volcano Alert Level was raised to Watch.

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.

Source: US Geological Survey Alaska Volcano Observatory (AVO)