|Start:||January 2, 2009 ± 30 Minutes||Observed|
|Stop:||January 21, 2009 ± 2 Days||Observed|
|Tephra plume: ||
|ColHeight: ||6000 m ||
|Duration: ||2 short bursts of possible explosive eruption observed within 19 days ||
On December 23, 2008, AVO noted a persistent thermal anomaly at Cleveland and raised the volcanic alert level and the aviation color code to Advisory/Yellow on December 24. Clouds obscured satellite views of Cleveland until December 28, when a clear view showed that the December 23 anomaly persisted.
From McGimsey and others (2014): "On January 2, 2009, a brief but explosive ash emission was detected in satellite images. The plume was visible in satellite images for several hours, rose to about 20,000 ft (6 km), and drifted east-southeast up to 240 km (150 mi) downwind dispersing harmlessly over the North Pacific. Flowage deposits draped the flanks with the two largest flows (about 100 m wide; 328 ft) extending down the northeastern and northwestern flanks for at least 2 km (1.2 mi). The eruption produced airwaves that registered on seismometers on adjacent Umnak and Unalaska Islands, as well as on a pressure sensor at Shishaldin Volcano on Unimak Island. Similar airwaves were observed from the November 3, 2008 eruption of Cleveland (M. Haney, AVO/USGS, written commun., 2009, AVO internal log entry).
"No further activity was noted until the end of January when satellite images showed evidence of recent eruptive activity visible around the summit of Cleveland. Retrspective analysis on January 23 of prior satellite data indicated that a short-lived, low-level ash emission may have occurred early on the morning of January 21."