October 10, 2005
Monday

Two remote Aleutian Island volcanoes grumbled to life this week, one spitting an ash cloud almost three miles high and the other shaking its uninhabited island with a growing swarm of little earthquakes.

Both Cleveland and Tanaga volcanoes lurk beneath one of the world's major airline highways, connecting North America with Asia through dozens of flights per day. Volcanic ash from an eruption could damage or destroy jet engines.

Cleveland Volcano blasted a small amount of ash from its summit early Friday morning, producing a cloud detected by satellites as it drifted 90 miles east-southeast of Dutch Harbor.

The 5,676-foot volcano, about 940 miles southwest of Anchorage, was listed as code orange, meaning it could produce an eruption without warning.

The ash cloud had disappeared by late morning, the observatory said.

Tanaga Volcano, which began trembling with tiny earthquakes earlier in the week, suddenly shook harder and more frequently early Friday morning. The observatory boosted its status from "dormant" to a yellow "restless" warning level. The 5,925-foot volcano rises from an uninhabited island 1,230 miles southwest of Anchorage.

Meanwhile, Spurr Volcano continued a yearlong episode of unrest with wee quakes and hot gassing. The stunning 11,070-foot white massif on the horizon 80 miles due west of Anchorage produced more quakes this week but appeared no closer to an eruption, the observatory reported.

In a status report released Sunday afternoon, the observatory reported no significant changes at the three volcanoes, based on new satellite images, pilot reports and sensor readings at Tanaga and Spurr.

More than 40 volcanoes rimming Alaska's Pacific coast have erupted in historic times, including three volcanoes in Cook Inlet that have blown their tops since the 1980s. Spurr last dusted Anchorage with ash in 1992.

The observatory has so far installed seismic listening posts on 28 volcanoes to catch early warning of unrest, but Cleveland is not one of them. Scientists must monitor its activity using satellite images and reports from pilots.

Cleveland forms the rugged western half of uninhabited Chuginadak Island, about 45 miles west of the village of Nikolski. It has erupted or produced ash at least 22 times since 1774.

Four years ago, Cleveland exploded three times, sending ash clouds seven miles into the sky and floes of rubble and lava down its slopes. The mountain also produced small ash clouds in July.

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