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4.1 earthquake comes as scientists watch Alaska's Iliamna volcano

Ben Anderson

On Wednesday, the Alaska Volcano Observatory issued an alert that they were closely monitoring Iliamna Volcano, 130 miles from Anchorage on the lower west side of Cook Inlet, following a period of increased seismic activity. That was before a moderate earthquake struck the upper Cook Inlet region in the wee hours of Thursday morning that many residents of Alaska's largest city may have woken up to.

"Over the past three months, there have been several episodes of increased earthquake activity at Iliamna Volcano," the AVO said. "One of these episodes is currently ongoing, and is characterized by numerous small earthquakes. This increase in earthquake activity may be related to movement of magma at depth, and additional observations including an airborne gas sampling and observation flight are being planned."

Despite the warning, the alert level for the 10,016-foot volcano remained at "Green," meaning that no eruptive activity or potential for imminent eruption was evident. Iliamna has no record of eruptions, though it has gone through similar periods of increased seismicity in the past. The AVO notes that an incident in 1996-97 was similar, though it didn't result in an eruption. 

The alert was issued prior to a magnitude-4.1 earthquake Thursday morning that may have woken some Southcentral Alaska residents. It was located less than 40 miles from Kenai, Soldotna, and Anchorage.

That earthquake was a fairly comfortable distance from Iliamna volcano -- about 100 miles -- but was the second earthquake in the past few days that set Southcentral Alaskans on edge.  A magnitude 3.6 temblor took place Monday under Prince William Sound and a mere 16 miles from the ski resort town of Girdwood.

Elsewhere in Alaska -- Mount Cleveland, an active volcano in the Aleutian Islands that has been on-again, off-again when it comes to volcanic activity -- showed some signs of life of its own when remote seismic sensors detected a short explosion in the vicinity of the volcano. Located on an uninhabited island, there is no real-time monitoring set up at Cleveland volcano, so researchers weren't able to immediately determine if there had been any ash emission resulting from the explosion.

It's been an active couple of months for Alaska volcanoes: Cleveland rumbled back to life on Jan. 31, continuing an ongoing flirtation with eruption continuing from last year. Another Aleutian volcano, Kanaga, briefly came alive in mid-February before being downgraded in the early part of March.