EMO surveys Anatahan eruptions

The restless rumblings of the volcano on Anatahan continues, with a joint report from the Emergency Management Office and the U.S. Geological Survey indicating that since Monday, the size of the explosions would plunge, surge, and plunge again.

The report showed that since Jan. 6, the magnitude of the explosion signals increased slowly and by midnight, had doubled, with explosions occurring every three to 10 seconds.

On Jan 10, the magnitude of the eruptions decreased before surging again at 6pm, doubling in strength and then decreasing by midnight.

EMO’s Juan Takai Camacho said yesterday that the trend remains and that the EMO would continue to work with the USGS in monitoring the volcano’s activity.

Camacho and others from EMO took part in an expedition flight over the island on Friday. They reported ash rising well above 5,000 feet.

“A dome is visible in the crater and [rocks] were observed [being thrown up] less than 2,000 feet,” a part of the report reads.

The third historical eruption of Anatahan began on Jan. 5, with occasional small long-period events noted as early as Jan. 2, followed by harmonic tremor on Jan. 4, which increased in strength through mid-day of Jan. 5. Harmonic tremor are continuous rhythmic earthquakes that can be detected by seimographs. Harmonic tremors often precede or accompany volcanic eruptions.

“The ash plumes likely extends 100km or more downwind at this time,” the report indicated. “This ongoing strombolian eruption is very similar in nature and size to the previous eruption of April-July 2004.

The island remains off limits since 2003, when Gov. Juan N. Babauta placed restriction on all travels to the island except for scientific expeditions, citing that although the volcano is not currently dangerous to most aircraft within CNMI airspace, conditions may change rapidly.

Aircrafts should pass upwind of the island or farther than 100km downwind and otherwise exercise due caution within 50km.

Also, the public is urged to be on the alert for any change of wind direction, which may result in ash and gas plumes affecting the southern islands.

Earlier, EMO director Rudolfo Pua said people should prevent water from being contaminated by the ash by covering water catchments containers and also urged individuals with respiratory problems to minimize outdoor activity and stay indoors.

Anatahan, an uninhabited island located 120km north of Saipan, had no historical eruptions prior to 2003.

On May 10, 2003, an eruption sent ash to over 30,000 feet and deposited about 10 million cubic meters of materials over the island and sea. A very small craggy dome extruded during late May and was destroyed during explosions on June 13 and 14, after which the eruption ceased.

A second eruption began on April 9, 2004 and ended on July 26.