02/19/2012 04:04 pm ET Updated Apr 20, 2012

Alaska's Aleutian Islands Volcano Could Erupt, Scientists Say

By Yereth Rosen

ANCHORAGE, Alaska Feb 19 (Reuters) - A volcano in Alaska's Aleutian Islands has rumbled to life and is at risk of a sudden explosion, scientists said on Sunday.

Kanaga Volcano, located 1,200 miles southwest of Anchorage near the port city of Adak, had a tremor Saturday morning followed by other seismic activity for about an hour, said the federal-state Alaska Volcano Observatory.

After that, satellite data detected what is believed to be a thin ash cloud emitted from Kanaga, the observatory said.

The activity prompted the observatory to issue a code-yellow advisory for air travelers and others in the region.

"This new unrest indicates a possibility for sudden explosions of ash to occur at any time, and ash clouds exceeding 20,000 feet above sea level may develop," the observatory said in its advisory.

The last eruptions from 4,288-foot Kanaga were in 1994 and 1995 , when the volcano sent up ash clouds, dusted the nearby community of Adak and disrupted air traffic, according to the observatory.

Adak is a former Navy station that has been converted into a service center for the North Pacific commercial fisheries fleet.

The town has about 330 residents, a state-owned airport left over from Navy operations, a seafood processing plant and numerous maritime-service operations.

Kanaga's new activity comes as another restless Aleutian volcano also has shown signs that it might explode and send ash clouds into the atmosphere.

Cleveland Volcano, located on an uninhabited island 940 miles southwest of Anchorage, had an ash-producing explosion in late December. It has been active since July, mostly oozing lava up through its summit crater, where the lava hardens into a dome.

That lava movement is continuing, according to satellite data monitored by the Alaska Volcano Observatory. A new lava dome, about 60 meters wide, now stands at the crater, replacing a bigger dome that was blasted away by the December explosion, according to the observatory.

Lava domes such as that atop 5,676-foot Cleveland Volcano could trap pressure and trigger explosions, observatory scientists have said.

The observatory has issued a code-orange watch for Cleveland Volcano site to alert aviators and others.

Though Cleveland and Kanaga are remote, ash-producing eruptions at either are consider potential aviation threats, as they lie along major aviation routes between North America and Asia. (Editing by Dan Whitcomb and Ellen Wulfhorst)