Alaska's Redoubt volcano erupts

ANCHORAGE, Alaska (Reuters) - After several weeks of tremors and intermittent steaming, Alaska's Mount Redoubt volcano erupted with a burst of ash that rose more than 9 miles (15 km) with more eruptions expected.

The first blast occurred at 10:38 p.m. Pacific time on Sunday (5:38 a.m. British time Monday), the Alaska Volcano Observatory said, followed by four smaller eruptions.

The 10,197-foot (3,108-metre) volcano, located 106 miles (170 km) southwest of Anchorage, Alaska's largest city, had been showing signs of a pending eruption for about two months. So far Anchorage has been untouched by harmful volcanic ash.

"There were five explosive events," said Tina Neal, a geologist at the Alaska Volcano Observatory, each lasting about 10 to 20 minutes.

"Each event sent up an ash cloud as high as 50,000 (15,240 meters) and possibly 60,000 feet (18,288 meters)," Neal said.

The observatory issued a red aviation code, warning airlines to steer planes clear of the area.

The bulk of the ash was blown at the 30,000-foot level, and is not reaching well-populated areas, Neal said. It was blowing north-northeast and had been reported in the tiny community of Skwentna and possibly in Talkeetna.

"The volcano is still restless," she said. "We'll be watching it very closely. It is highly unstable still and further eruptions are likely."

The latest round of seismic activity at Redoubt started in January, prompting the Alaska Volcano Observatory to put it on an alert status and, at times, have staff on duty around the clock.

Residents of Anchorage and other communities in the region had prepared for an eruption by buying breathing masks for possible ash contamination and stocking up on some food and water.

The volcano last rumbled to life in December 1989, erupting multiple times over a period of weeks. The eruptions sent ash plumes almost 8 miles high and the first event nearly downed a KLM jetliner.

(Editing by Bill Rigby and Bill Trott)