First it was Alaska's Mount Cleveland that awoke and threatened to erupt. Now Kanaga, another Alaska volcano is growing restless.

This weekend, the Alaska Volcano Observatory raised the threat level to yellow on Kanaga, located on Kanaga Island, one of the most southerly of the central Aleutian Islands chain.

"Somewhat elevated seismicity continues at Kanaga Volcano," the observatory reported, adding that on Saturday a weak ash cloud may have been detected after a volcanic tremor.

Kanaga Volcano last erupted in 1994-1995. At least two significant ash plumes were recorded over the course of this eruption. The Aleutian community of Adak received a light dusting of ash and air traffic was disrupted due to continuing low-level activity and cloudy conditions, which prevented visual approaches to the Adak air field.

Mount Cleveland threat at orange

Meantime, scientists continue to monitor Mount Cleveland, which is located on Chuginadak Island, a remote and uninhabited island in the east central Aleutians.

Cleveland's current threat level is orange, with the observatory reporting a new 200-foot-diameter lava dome.

"There have been no observations of ash emissions or explosive activity during this current lava eruption," according to Alaska Volcano Observatory.

Seismic activity has occurred on and off for nearly 90 years at Cleveland, according to the observatory, though events have become more frequent over the last 20 years. Cleveland's become rather active over the last eight months, building lava domes and producing what volcanologists call "geothermal activity." That activity climaxed on Christmas Day 2011 and a few days later, when the volcano spit ash 15,000 feet into the air, threatening international travel.