This is a questionable event.
|Start:||September 12, 2010 ± 1 Days||Observed|
|Tephra plume: ||
|ColHeight: ||7620 m |
On August 26, 2010, citing a persistent thermal anomaly, AVO raised the level of concern color at Cleveland from UNASSIGNED to YELLOW, and the alert status from UNASSIGNED to ADVISORY. Because Cleveland lacks a real-time seismic network, AVO is unable to track local earthquake activity.
AVO continued to detect intermittent thermal anomalies (weather permitting) until September 4, 2010. Satellite views were then obscured by clouds until September 7 and 8, when clear-weather views of Cleveland showed no thermal anomaly. On September 10, 2010, AVO lowered the level of concern color code and alert status to UNASSIGNED.
On September 12, 2010, AVO again raised the level of concern color code to YELLOW and the alert status to ADVISORY, based on detection of thermal anomalies and the presence of a possible ash plume drifting east from the volcano. The estimated plume height was about 25,000 ft asl.
AVO continued to detect thermal anomalies on September 14, 15, 25, 26, and October 1. During the other days, clouds prevented satellite observation of Cleveland. Although the weather usually prevented observations of Cleveland, weak thermal anomalies were also detected on October 14, October 19, October 25, and October 29. Clouds completely obscured observations for the week of November 1- 6, but thermal anomalies were again detected on November 7. The weather then remained cloudy until November 16,17, 25, 28, and 30, when thermal anomalies were again visible.
The poor viewing weather continued during December, but thermal anomalies were recorded on December 6, 13, 14, 23, and 27.
Similar conditions continued in January, 2011. Weak thermal anomalies were visible on January 1, 11, and 16, and the weather remained cloudy for the remainder of the month.
In February, a weak thermal anomaly was observed on the first. On the 9th, a pilot overflew Cleveland and reported minor, repetetive steam emissions rising hundreds of feet above the summit. The snow on the flanks was pristine, with no indication of recent ash emissions. Steam emissions are common at Cleveland and do not indicate an increased level of unrest.
In March, a weak thermal anomaly was observed on March 2, 3, and 11. A cloud-free view of the volcano on March 23 showed no unusual activity. On March 31, 2011, AVO lowered the volcano alert to UNASSIGNED and the aviation color code to UNASSIGNED, on the basis of a lack of confirmed eruptive activity over the past several months.