Frequent explosions continue at Anatahan

Anatahan remains active and continues to erupt with frequent Strombolian explosions, according to the latest joint report from the Emergency Management Office and the U.S. Geological Survey.

Strombolian eruptions are discrete explosions of relatively fluid lava from a single vent. It is thought that they originate when large gas bubbles rising within the conduit burst at the partly solid surface of the magma column inside the vent.

In their report, the agencies indicate that shortly after 10pm Thursday, there was an unusually quiet 15-minute span featuring only one very small explosion.

Before the DSL service went down at EMO on Friday, however, seismic signals indicated that eruption level was about two-thirds of its previous peak.

Over the past several days, the volcano has sent ash as high as 15,000 feet and possibly up to 20,000 feet.

“Explosions are likely still occurring at a rate of several per minute,” the agencies reported.

Satellite imagery also shows ash trailing more than 100 nautical miles westward and vog—volcanic smog—more than 400 miles westward.

Anatahan’s third historical eruption began on Jan. 5. Several ash and haze advisories had been issued since then, whenever winds change direction and carry them across the southern islands.

The first historical eruption of Anatahan began on May 10, 2003, sending ash to over 30,000 feet and depositing about 10 million cubic meters of material over the island and sea. The eruption ceased on June 14 before erupting again on April 9, 2004. That eruption ended on July 26, 2004.

The island remains off limits, with the exception of scientific expeditions conducted by EMO and the USGS.

USGS geologist James Quick said the hazards posed by the eruption is limited to the island itself, as well as local aviation, but that the situation could change quickly.

Possible scenarios include larger explosions accompanied by pyroclastic flows. Very large explosions are unlikely, though, because pressure is currently being released.

He added the eruptions are also not likely to have a major impact on aviation or generate a tsunami that would have Marianas-wide effects.

Meanwhile, EMO and the National Weather Service on Guam maintain their high surf and small craft advisories for the Marianas.

“Strengthening trade winds are generating a large northeast swell which will produce hazardous surf for the islands into next week,” the agencies said. ”A high surf advisory remains in effect for the Mariana Islands.”

Coastal water forecast for Guam, Tinian, Rota, and Saipan feature surf of 9 to 11 feet. The hazardous surf is expected to continue building up, eventually peaking on Tuesday at 13 to 15 feet.

Due to the high risks of dangerous rip currents and high surf in the region, the public is advised to avoid venturing to exposed beaches and reef lines on north- and east-facing coasts, citing that the events are life threatening for anyone entering the water.