According to the Alaska Volcano Observatory, the aviation color color code and the alert level of Cleveland Volcano was upgraded on Tuesday to "Orange" and "Watch" to reflect new satellite data indicating increased activity.
The east central Aleutian Chain volcano, which sits 45 miles west of the community of Nikolski, has spent much of the past year teasing that it would erupt, and its status has alternated between "Yellow/Advisory" and the more serious "Orange/Watch" four times since July 2011.
The AVO reports that the lava dome that had developed at Cleveland last year was mostly removed by a brief explosive episode at the end of December. But new satellite images indicate that a fresh lava dome, approximately 130 feet in diameter, has formed in the summit crater.
There have been no explosions or ash emissions detected during the current lava eruption, but the AVO notes that it remains possible for intermittent, sudden explosions of blocks and ash to occur at any time, and ash clouds exceeding 20,000 feet above sea level may develop.
Because Cleveland is not covered by real-time seismic sensors, such explosions and their associated ash clouds may go undetected in satellite imagery for hours.