Anatahan acts up anew over weekend

Anatahan’s eruption intensified over the weekend, with ash and gas streaming continuously from the volcano into the atmosphere.

Volcanic activity started to step up on Friday, when seismic signals showed that larger and longer period of ash emissions were occurring.

The seismicity further increased on Saturday, approaching the highest level for this year, which happened in late April. Air Force Weather Advisory reported that its satellite could see Anatahan as a hot spot on that day, while EMO noted a plume of light ash trailing a few tens of kilometers downwind from the volcano at altitudes less than 10,000 feet.

EMO, however, said that the seismicity level decreased yesterday from its very high level on Saturday.

“The seismic signals indicate that the frequent individual explosions of a couple of days ago have decreased dramatically in size and number. Instead, ash and gas stream continuously into the atmosphere,” the agency said. “EMO personnel Joe Kaipat visited the island with personnel from Fish and Wildlife and reports an ash plume probably a few tens of kilometers long moving northeastward from the volcano.”

In an interview, EMO director Rudolfo Pua said the storm brewing at the eastern side of the Mariana islands chain was causing Anatahan’s increased activity.

But he told the public not to worry, as a big eruption is not likely to happen soon since the volcano is still able to vent pressure.

“What worries me is when the ventilation or the opening of the crater closes and pressure starts to build within. Then we will have an explosive eruption,” Pua said.

All travels to the island remain restricted, except for scientific expedition, EMO said. Aircraft are urged to pass upwind of Anatahan or farther than 30 km downwind from the island, and exercise due caution within 30 to 50 km of Anatahan.

“Although the volcano is not currently dangerous to most aircraft within the CNMI airspace, conditions may change rapidly,” EMO said.

Gov. Juan N. Babauta declared island “off-limits” just days after the volcano’s big eruption on May 10 last year. The volcanic activity eventually slowed down, but regained intensity last March 30.

According to EMO, a more energetic seismicity stage began on April 24, when a light ash cloud rose to a few thousand feet. Seismic activity peaked on April 28, then decreased slowly to about half that level in May.

In June, the seismicity level was higher, with more frequent small explosions every few tens of seconds, and a 100-km-long, light-colored plume of steam and ash occasionally visible. An active spatter cone has existed since at least June 10, from which continuous strombolian explosions were throwing material as high as 100 m every few tens of seconds to minutes. The spatter filled up the inner crater by about July 10, EMO said.