Alaska Volcano Observatory

From Dixon and others (2015): "AVO continued to observe persistently elevated surface temperatures in satellite data (weather permitting) throughout the spring [of 2013]. At 12:59 UTC (04:49 AKDT) on May 4, the Okmok infrasound and seismic networks recorded an explosion from Cleveland. In response, AVO raised the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH. A small ash cloud was first visible in satellite imagery at 13:48 UTC (06:48 AKDT). Over the next 3 hours, a small, detached cloud moved east and then southeast from the volcano and was last discernable about 200 km (125 mi) downwind. The explosion was followed by a period of infrasonic tremor interpreted as continuous low-level emissions (gas and [or] ash) from the vent. May 5 satellite images, including an unusual elevated temperature signal in AVHRR data, showed a small patch of ash at the Cleveland summit (fig. 41). Residents of Nikolski, 74 km (46 mi) away, reported a booming noise about 8:00 p.m. local time on the same day; however, no correlative explosion was detected with infrasound or other techniques.
"On May 6, infrasound sensors and analysis of airwave signals detected three explosions from Cleveland (table 8 in original text). Satellite observations that day showed that the Cleveland summit crater filled nearly to the rim with tephra; the crater floor was marked by a 15 m (57 ft) diameter vent. New flowage deposits, including a lobe of lava (identified days later during reanalysis), extended down the upper northeastern, eastern, and southeastern flanks of the volcano. The lava flow lengthened over the next week, suggesting continued extrusion of lava from the summit vent. Details of the timing of lava extrusion with respect to explosions on May 6 remain unclear. Satellite images into June captured elevated temperatures in the summit area related to this activity (fig. 42 in original text).
"Cleveland remained at Aviation Color Code and Volcano Alert Level ORANGE/WATCH until June 4, when AVO downgraded the status to YELLOW/ADVISORY. On July 26, analysis of a Landsat 8 image suggested new lava within the summit crater (fig. 43 in original text); it is possible extrusion of this lava occurred during a period of elevated temperatures and visible plume from the Cleveland summit during the prior week. AVO remained at YELLOW/ADVISORY and apparently this new lava never overtopped the crater rim, as it had in early May.
"From early July through the end of 2013, AVO's infrasound and seismic networks detected a number of additional explosions and periods of infrasonic tremor at Cleveland (table 8 in original text). Most of these events did not have an accompanying ash signal in AVHRR satellite images, suggesting minor to no ash emissions during the events. It is entirely possible that very brief emissions of ash went unnoticed because of weather and gaps between satellite passes.
"On December 28, a Cleveland explosion triggered the AVO infrasound alarms on both the Okmok and Akutan arrays at 21:29 UTC (12:29 AKST). Strongly elevated surface temperatures in the summit area appear in a satellite image 10 minutes prior to the explosion. Following a second explosion 2 days later, a small ash cloud was visible 73 km (45 mi) north of the volcano. Despite this activity, AVO remained at Aviation Color Code and Volcano Alert Level YELLOW/ADVISORY because these ash clouds were quite small, likely less than 20,000 ft ASL, and short-lived.
"The 2013 activity at Cleveland is a continuation of the intermittent explosive and effusive activity that has occurred for much of the time since its last significant eruption in 2001 (Dean and others, 2004)."
Cleveland began 2014 with three explosions generating minor ash plumes. Explosions were detected on December 28, December 30, and January 2. On January 2, citing increased explosions and minor ash plumes, AVO raised the Aviation Color Code and Alert Level to ORANGE/WATCH. Analysis of satellite, wind, and ash dispersion data indicates that the Dec 30 and Jan 2 plumes probably did not reach more than 15,000 ft above sea level. No new activity was observed after the January 2 explosion, and AVO lowered the Color Code/Alert Level to YELLOW/ADVISORY on January 10, 2014.
Other than weakly elevated thermal anomalies in satellite imagery, no activity was observed at Cleveland until February 19, 2014 when a small steam plume was observed. On February 24, satellite data detected increased heat at Cleveland's summit. The following day, infrasound and lightning and alarms detected two small explosions at Cleveland Volcano at about 4:17 UTC February 25 (19:17 AKST February 24) and 10:35 UTC (1:35 AKST) February 25. Satellite data available several hours after these events occurred confirm that small ash clouds were generated by the explosions. The events were brief, and the estimated altitude of the drifting ash clouds was about 5 km (16,000 ft) asl. Satellite obsevations following the explosion show deposits of ash and large lava blocks on the upper flanks, extending 2.5 km (1.5 mi) from the summit. This suggests that these explosions were more energetic than those commonly observed over the past several years. However the ash emissions were brief and relatively low altitude, typical of recent Cleveland activity. The Color Code/Alert Level remained at YELLOW/ADVISORY.
From Cameron and others, 2017: "On March 6, residents of Nikolski village on the southwestern end of Umnak Island 73 km (45 mi) northeast of Cleveland reported dark ash rising from Cleveland at about 03:30-04:00 UTC on March 7 (6:30 or 7 p.m. AKST, March 6). In later discussions by telephone, residents further reported that, over a period of about 40 minutes, before the volcano became obscured by weather, alternating clouds of white steam and dark ash rose above the summit; the dark ash clouds rose about twice as high as white clouds but both dissipated quickly. Similar activity had been noted several months prior, so it is likely that other small episodes of ash emission have gone undocumented in the AVO database of eruptive activity from Cleveland during cloudy conditions
when visual observations could not be made. The activity on March 6 was too ephemeral or small to be noted even in clear satellite views."