AVO reported that numerous earthquakes at Cleveland have been detected by the local seismic network during the previous week and 37 of the events were large enough to be located. Earthquake hypocenters shallowed from depths of less than 18 km during the beginning to depths less than 6 km by the end of the week. The earthquakes were small, at magnitudes less than 2, but the rate of events was unusual for Cleveland. The seismicity along with elevated surface temperatures at the summit crater frequently identified in satellite images and continued gas-and-steam emissions suggested an increased likelihood of a future eruption. The Volcano Alert Level for Cleveland to Advisory (the second level on a four-level scale) and the Aviation Color Code to Yellow (the second color on a four-color scale) at 1218 on 19 July. Earthquakes continued to be detected (but were too small to be located) during 21-23 July. Weather clouds mostly obscured views of the volcano in satellite and web camera images, though minor steaming from the summit occurred during 23-24 July.

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)