© T. Keith, U.S. Geological Survey
Although Bogoslof Island is uninhabited, it is an important breeding ground for sea birds, seals and sea lions.
Seismic unrest continues at Bogoslof volcano. Scientists are watching the eruption around the clock — even though monitoring stations are far from the site.

Chris Waythomas, of the U.S. Geological Survey, is observing a particular indication of increased seismic activity: volcanic tremors.

"You can think of it as the sort of signal you might get if you were to seismically monitor an organ pipe," Waythomas said. "As air moves through the pipe, it resonates. When it impinges on the pipe, it produces motion and that's what we're kind of measuring."

Waythomas said the problem is there's a lot of wind and that can obscure the signal.

"It looked to us like there was increase in this tremor signal," Waythomas said. "We wanted to alert everyone it was possible this could be accompanied by a large steam or ash emission."

The Alaska Volcano Observatory also has access to satellites which they use to look for steam or ash plumes and thermal signals, but cloud cover is making it difficult to confirm.

Bogslof volcano began erupting last week.