ANCHORAGE — Diminished earthquake activity led authorities Thursday to reduce the warning levels at two volcanoes on an uninhabited island in Alaska’s Aleutian chain because of the decreased potential for eruptions.
The Alaska Volcano Observatory lowered the warning level to “Advisory” status from “Watch” for both Tanaga and Takawangha volcanoes on remote Tanaga Island, located about 1,250 miles southwest of Anchorage.
A swarm of earthquakes between March 9 and 11 signaled the increased chance of eruptions. However, since then, the rate and magnitude of quakes have decreased.
Several quakes per minute continue to be recorded under Tanaga Island, and the largest recorded in the last day was a magnitude 3.1 between the two volcanoes, separated by about 5 miles. During the peak, the quakes had magnitudes up to 4.0.
No other signs of unrest have been detected, a statement from the observatory said.
Tanaga is the middle of three volcanoes on the island, with Takawangha located to the east. A third volcano on the island, Sajaka, is about 2 miles to the west of Tanaga, and was not showing any sign of activity.
Since the island has no residents or structures, there was little chance of damage from the thick, viscous lava flows in an eruption. However, an ash cloud could pose threats to aircraft, potentially disrupting air travel between North America and Asia, and health problems for communities farther away.
The nearest community, Adak, is about 65 miles to the east, on a separate island.
The last known eruption for Tanaga was in 1914. It erupted twice in the late 1700s and again in 1829.
The observatory has said there are no known eruptions of Takawangha or Sajaka. However, field work has indicated that eruptions may have occurred from those volcanoes and misattributed to Tanaga.
