It's been nearly 20 years since Alaska's Mount Redoubt erupted, but that time of tranquility might end.

Recent seismic activity could be a prelude to an eruption, "perhaps within hours to days," said geologists from the Alaska Volcano Observatory.

The 10,197-foot peak sits about 50 miles west of Kenai and 100 miles southwest of Anchorage. It last erupted during a five-month stretch beginning December, 1989.

Recent activity began around 1 a.m. Sunday, then it eased about five hours later.

It was still well above normal "background" tremor levels, said Dave Schneider, a volcanologist from the observatory.

An observatory crew flew over Redoubt, and it ruled there had been no eruption.

"There was steaming through pre-existing holes, but there were no new holes. ... and there was no ash on the snow cover," he said.

But during the flyover, crew members smelled sulfur, so observatory staff will be monitoring activity and satellite images that identify temperature changes round the clock, Schneider said.

Observers will also look to weather radar scanners near the Kenai airport for help. Those scanners send data in six-minute intervals.

These scanners will be able to detect an ash plume should one appear, Schneider said.

Twenty years ago, an eruption forced mud flows from Redoubt into the Drift River drainage. The flows also caused partial flooding of the Drift River Oil Terminal facility.

Additionally, the ash plume disrupted international air traffic and a thin ash layer coated Anchorage and surrounding communities.

Sunday's volcanic activity came on the heels of a magnitude 5.7 earthquake at the mouth of Cook Inlet.

However, Schneider said that does not necessarily mean the earthquake stirred the volcanic activity. With the two events being more than 100 miles apart, it's even more unlikely, he said.