The Alaska Volcano Observatory is again raising the threat level for a remote volcano near the Aleutian Islands. The observatory says seismicity at Pavlof Volcano increased Thursday. Web camera images Friday showed minor steam emissions. That observatory raised the aviation advisory color code from green to yellow, one step above normal volcanic activity. Pavlof is about 625 miles southwest of Anchorage. On March 27, the volcano sent an ash cloud to 37,000 feet, which led to canceled flights in interior and northern Alaska. The observatory says pauses in activity lasting for weeks to months have occurred during past eruptive episodes. Pavlof erupted intermittently for more than two years from April 1986 to August 1988. The volcano has erupted more than 40 times since record-keeping began in the late 1700s.