Anatahan eruptions decrease

The volcanic eruptions on Anatahan have somewhat decreased since peaking on Sunday but they remain frequent and strong, according to a joint report issued by the Emergency Management Office and the U.S. Geological Survey.

After subsiding in the past days, the eruption abruptly changed and intensified, peaking at about 7am Sunday morning, based on reports of airline pilots ash, who described ash clouds rising up to 10,000 to 15,000 feet.

Seismicity indicates that the explosions decreased but remain frequent and strong, EMO and USGS said.

The third historical eruption of Anatahan began on Jan. 5 preceded by two days of small long-period earthquakes and a day of harmonic tremor.

Pyrolastic rocks of 1 meter or more in diameter and ash were observed by EMO personnel during a recent overflight being thrown up hundreds of meters in the air and falling back down, creating a cinder cone about 120 meters in diameter.

The explosions peaked on Jan. 9, occurring every three to 10 seconds before stabilizing.

The eruption stopped twice between Jan. 15 and Jan. 19, ceasing for a few hours before swiftly resuming at higher intensity. Satelitte photos showed a plume of vog trailing about 60km downwind.

From Jan. 20 to early Jan. 22, the seismicity dropped abruptly, indicating that the explosions have ceased.

EMO and USGS indicated that the pause in seismicity, punctuated occasionally by an hour or two of low amplitude tremors, may be an indicator that the eruptive phase is winding down.

Anatahan, an uninhabited island 120 miles north of Saipan, remains off limits until further notice.

Anatahan had no historical eruptions prior to 2003. On May 10, 2003, an eruption sent ash to over 30,000 ft and deposited about 10 million cubic meters of material over the island and sea. The eruption ceased in June.

The second phase of eruptions began about April 9, 2004 and ended on July 26, although visitors to the island three months later could still see very small amounts of steam and ash rising 100-200 ft above the crater rim and could smell sulfur dioxide near the crater.

Meanwhile, the EMO, together with the National Weather Service on Guam, reminds the public that the high surf advisory on Saipan, Tinian, and Rota remains in effect.

EMO forecasted gentle to moderate winds and dry weather for the islands today but strong northeast trade-wind flow that passed the islands last week is still brining hazardous surf.

“Expect hazardous surf heights of 7 to 9 feet along…through Tuesday,” EMO said.

The public is urged to avoid venturing to exposed beaches and reef lines due to the high risk of rip currents and dangerous surf.