A plume of ash spews from the Cleveland Volcano in 2006.
updated 8/4/2011 6:01:54 PM ET 2011-08-04T22:01:54

A lava dome atop the massive Cleveland Volcano in Alaska's Aleutian Islands has gotten larger in the past week, and officials keeping an eye on the restive mountain have raised eruption threat levels.

The lava dome, a viscous mass of lava belched up from inside the mountain but too thick to flow down its sides, widened by 33 feet over five days, to 164 feet across.

On the fifth day, Aug. 2, the Alaska Volcano Observatory raised the volcano alert level to "watch" and aviation color code to orange, the second-highest levels in each four-level scale.

"The presence of the lava dome increases the possibility of an explosive eruption but does not necessarily indicate that one will occur," the latest report from the AVO stated.

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The agency added that it does not anticipate any threat to air traffic from ash plumes or other airborne debris should Cleveland erupt. "Lava flows onto the flanks of the volcano may develop but would not be hazardous to aviation," the report said.

The 5,676-foot-tall volcano, on the uninhabited island of Chuginadak, has erupted more than 20 times since 1828. The last eruption occurred over the course of a week in late July.

The mountain is part of the infamous Ring of Fire, a string of volcanoes strewn around the perimeter of the Pacific Ocean that produces some of the world's most dramatic and dangerous eruptions.

The Cleveland Volcano could put on quite a show in coming days.

"Short-lived explosions could produce an ash cloud that exceeds 20,000 feet above sea level," according to the AVO report. "These events can occur without warning and may go undetected in satellite imagery for hours."

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