Swarms of earthquakes at two Alaskan volcanoes raise fears of a possible eruption

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How do volcanoes make “pellet hair”?

As Hawaii’s Mauna Loa volcano wakes up from a decades-long slumber, officials are warning residents of the area not only of falling ash and airborne gases, but also of the possible presence of volcanic fiberglass known as “pellet hair.”

On Friday, earthquakes rocked only one volcano on the same island in Alaska’s Aleutian chain, raising fears of a possible eruption.

High earthquake activity has been reported at both the Tanaga and Takawanga volcanoes on the uninhabited island of Tanaga, hundreds of miles (kilometers) from Anchorage.

“If an eruption does occur, it is uncertain at this point whether it will come from Takawanga or Tanaga,” officials with the Alaska Volcano Observatory said in a statement raising the alert level for the two volcanoes.

What is the latest?

Although the frequency of tremors diminished slightly on Friday, earthquake activity in the volcanoes was still occurring every minute or two.

Tanaga, November 2012. Photo courtesy of Roger Clifford.

“We still get earthquakes greater than magnitude 3 on a regular basis,” said John Bauer, a research geophysicist with the USGS stationed at the Alaska Volcano Observatory in Anchorage.

Seismic activity spiked earlier this week at Tanaga Volcano, the center of three volcanoes on Tanaga Island, located about 1,250 miles (2,012 kilometers) southwest of Anchorage, the state’s main population area.

Then in the middle of the week, earthquake activity began to intensify at Takawanga, a volcano about 5 miles (8 kilometers) east of Tanaga.

Read more: Century-dormant Alaskan volcano presents ominous warning signs: ‘major unrest’

“We’ve actually seen seismic activity gathering under and between both epicenters, which is causing us quite a bit of anxiety about what’s going on,” Bauer said. “It’s a very energetic sequence.”

The third volcano on the island, Sagaka, about 2 miles (3 kilometers) west of Tanaga, is showing no sign of activity.

What is the biggest threat?

Since the island is uninhabited, the thick, viscous lava that can flow out in an eruption will not cause any harm. The nearest community, Adak, is located about 65 miles (104 km) to the east, on a separate island.

However, the ash cloud can pose threats to aircraft, potentially disrupting air travel between North America and Asia, and health problems for faraway communities. Volcanic ash is angular and sharp and is used as an industrial abrasive. Rock powder can cause a jet engine to shut down.

The Interagency Volcanic Ash Response Plan, developed in 2011, outlines how state, federal, and local agencies should respond to a volcanic eruption in the region that could dump ash across the region. The Alaska Volcano Observatory is calling for taking the lead in confirming the eruption and notifying other agencies, which will alert pilots, sailors and local communities.

Where and how far any ashes will go will depend on many factors. Fine ash drifting into cities can cause respiratory problems for people and animals, interfere with electrical equipment and damage air filters and gasoline engines.

Does earthquake activity always mean imminent eruption?

The short answer is no.

Both the Takawanga and Tanaga volcanoes in 2005 had smaller seismic swarms that eventually died down without exploding—at least not something officials know about.

“We’ve seen some signs that it may have been very slight eruptive activity, but we’ve never been able to confirm that,” Bauer said.

Some of the active areas in 2005 are where scientists see a lot of seismic activity now. “Where and how this activity will end, whether or not it will lead to an eruption is an open question,” Bauer said.

How unusual is it for two active volcanoes to be so close to each other?

Having two volcanoes so close and both in turmoil is unusual for Alaska, Bauer said, although such incidents have occurred elsewhere in the world.

For example, Mauna Loa and Kilauea exploded around the same time last year on the Big Island of Hawaii.

“It is very unusual… that we are seeing earthquakes below both centers at the same time and in fact between the two centers, something that suggests to us that perhaps something larger is afoot here in the Earth’s interior and magma etc. under the volcanoes,” the authority said.

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