|Start:||July 19, 2011 ± 7 Days||Observed|
|Stop:||January 2013 ± 1 Months||Observed|
|Lava dome: ||
|Tephra plume: ||
On July 20, 2011, AVO raised the volcano alert level/aviation color code at Cleveland from unassigned to advisory/yellow, based on the presence of persistent thermal anomalies seen in satellite data on July 19 and 20. Thermal anomalies continued to be detected (weather permitting) on July 22, 26, and 30th.
On August 2, 2011, AVO raised the volcano alert leve/aviation color code to watch/orange, in response to a July 29 observation of a small lava dome (about 40 meters in diameter) in the summit crater. The lava dome was extruded some time after July 7, when the last clear view of the summit area was acquired. A weak thermal anomaly persists at the summit and may indicate slow dome growth or dome cooling.
On August 30, 2011, AVO lowered the Aviation Color Code to YELLOW and the Alert Level to ADVISORY based on the lack of thermal anomalies in satellite data for the two weeks prior, suggesting that dome growth had paused or stopped. The lava dome at this time was 80 meters (262 feet) in diameter.
Persistent elevated surface temperatures were measured in satellite data on September 3, 2011. Observations on September 6 showed that the lava dome resumed growth and now filled the crater floor. The size of the lava dome on September 6 was approximately 120 m (394 feet) in diameter. In response, AVO raised the Aviation Color Code to ORANGE and the Alert Level to WATCH.
September 9 analysis of TerraSAR-X satellite radar images through September 9 indicate that the dome now occupies the entire crater floor (about 150 m or 494 feet in diameter), but is still lower than the crater rim.
September 15, 2011: Satellite data show that the dome continues to grow and is 155 m in the E-W direction, 30 m below the lowest point of the crater rim.
September 20, 2011: Satellite data show that the dome continues to grow and is 165 m in the E-W direction, and 20 m below the lowest point of the crater rim.
By the first week of October, satellite images showed the lava dome was within 10 m of the crater rim on the southwest and east-northeast sides of the crater. Weather conditions were cloudy for much of October. An October 23 TerraSAR-X satellite radar image of Cleveland showed no discernable growth in the lava dome in the several weeks prior to the new image. The October 23 image also showed deflation or collapse of the dome.
On November 3, 2011, citing lack of dome growth evident in satellite images, AVO lowered the Aviation Color Code at Cleveland to YELLOW and the Alert Level to ADVISORY. Throughout November, weather permitting, AVO continued to observe thermal anomalies and steam plumes in satellite imagery, consistent with cooling of the emplaced hot dome.
Observations in early December 2011 show continued deflation and cooling of the lava dome, which is about 1 million cubic meters (1.3 million cubic yards) in volume.
On December 29, 2011, AVO observed a detached, drifting ash cloud to approximatly 15,000 ft ASL in satellite imagery. The plume was approximately 50 miles (80 km) moving ESE from Cleveland. Ground-coupled airwaves from the explosion were also detected at the distant Okmok seismic netowork - placing the time of explosion at 13:12 UTC, December 29. Based on the presence of an ash cloud, AVO raised the aviation color code back to ORANGE and the alert level to WATCH.
On December 30, 2011, with no new explosive activity, AVO lowered the aviation color code to YELLOW and the alert level to ADVISORY. Subsequent satellite images showed that the December 25 (recognized in retrospective data analysis) and 29 explosions had largely removed the dome.
One month later, on January 30, 2012, satellite data showed another small dome within the summit crater. As of January 30, 2012, the new dome measured about 40 meters in diameter. On January 31, 2012 (date of AVO's receipt of the satellite information), AVO raised the aviation color code to ORANGE and the volcano alert level to WATCH.
By February 10, 2012, the lava dome's size was estimated at 50 m in diameter, and it had grown to 60 m by February 17.
On March 8, 10, and 13, 2012, there were three small, short-duration explosion at Cleveland; detected by distant infrasound and seismic sensors. These explosions likely expelled the dome that had been in the summit crater.
On March 23, 2012, citing no further explosions or dome growth, AVO lowered the aviation color code to YELLOW and the alert level to ADVISORY.
On March 28, AVO again raised the aviation color code to ORANGE and the alert level to WATCH, due to the presence of a new dome in the summit crater, as viewed in satellite imagery.
On April 4, 2012, this new dome, which had grown to about 70 m in diameter, was destroyed during a short explosive eruption. This eruption was detected by distant infrasound and seismic stations, and had an ash cloud height of about 4.5 km. This was the third lava dome at Cleveland to be erupted and destroyed at Cleveland since July 2011.
The week of April 13 saw several ash-poor short explosions at Cleveland, without evidence of renewed lava extrusion.
Another explosion occurred on April 19 that generated a small ash cloud to 4-6 km. Satellite images taken after the eruption show block and ash deposits extending up to 1 km down the south flank of the volcano. After this explosion, a fourth lava dome began growing within the summit crater; this dome was about 25 m diameter on April 27. This fourth dome was destroyed sometime prior to May 4, in an explosion too small to be detected by the distant infrasound and seismic statiosn. Following that explosion, a fifth dome began extruding, although it was very short lived, and destroyed by small explosions on May 4th or May 5th.
On May 30, 2012, AVO again lowered the aviation color code to YELLOW and the alert level to ADVISORY.
On June 6, Nikolski residents reported a strong sulfur smell, and a low-level plume (3.5 km ASL) was observed in web camera images. Satellite images from June 9 and 10 showed deposits of minor amounts of ash, extending as far as 5000 feet (1.5 km) from the summit.
At roughly 22:05 UTC (14:05 AKDT) on Tuesday June 19, a pilot report, web camera images, and distant infrasound data detected an explosive eruption at Cleveland Volcano. The pilot report estimated the plume height at 35,000 feet (10 km). Satellite data suggest that the plume contained a relatively small amount of ash and was similar to other plumes produced by Cleveland explosions in the past year. In response to this event and heightened likelihood for more explosions, AVO raised the the Aviation Color Code/Volcano Alert Level to ORANGE/WATCH. No further explosions have been detected, though thermal anomalies have been observed in satellite data and steam/gas plumes have been visible in web camera images later in the week.
A small (25 m diameter) lava dome was observed growing in the summit crater by June 26; and another small explosion was detected by distant infrasound and seismic sensors in the wee hours of June 26.
Satellite data from 10:12 PM, July 11, 2012 (ADT) showed a low altitude, weak ash cloud. Elevated surface temperatures continued through July.
On Saturday, August 4, 2012, at 8:38 AM (ADT), a small explosive event occurred at Cleveland. This event was detected by retrospective analysis of infrasound data. Satellite images showed a brief, faint steam plume about 4 hours before the event. Another small explosion occurred on Friday, August 17, 2012. Images from this day also show no lava dome in the summit crater. This explosion was detected via seismic and infrasound instruments on nearby volcanoes. No ash cloud was observed in satellite imagery. This explosion was the twentieth at Cleveland since December 25, 2011. Another small explosion, this one with low-level ash cloud, occurred at 6:55 AM ADT on August 19. The ash cloud tracked to the southeast and dispersed over several hours.
On September 5, 2012, AVO lowered the aviation color code to YELLOW and the volcano alert level to ADVISORY, based on lack of eruptive activity since August 20. Cleveland remained cloudy for much of the rest of September and October.
On October 20, 22, and 24, elevated surface temperatures were again observed at Cleveland. These thermal anomalies were also observed during the first week of November, 2012.
On Sunday, November 10, 2012, a small ash cloud from Cleveland was detected in satellite views. Satellite images from 11:47 AM AST through 6:43 PM AST show the ash cloud, which was last observed about 60 miles south of Dutch Harbor. In response to this explosion, AVO raised the volcano alert level to WATCH and the aviation color code to ORANGE. Retrospective analysis of infrasound data suggests this explosion occurred at 11:25 AM AST.
AVO lowered the volcano alert level to ADVISORY and the aviation color code to YELLOW on November 21, 2012, based on no further explosions since November 10, 2012, and no evidence of lava dome growth during that time. Elevated surface temperatures persisted during partly or mostly cloudy views through the end of November and the first half of December, 2012.
Elevated surface temperatures were again observed in mid-January, 2013. More consistent high temperatures returned in late January, 2013.
Satellite data obtained on January 30, 2013, indicated a lava dome had grown in the summit crater of Cleveland. On January 30, the dome was about 100 m in diameter. AVO raised the volcano alert level to WATCH and the aviation color code to ORANGE. The color code was lowered to YELLOW again on March 8, 2013, citing no change in the summit lava dome, and declining thermal anomalies.