Anatahan volcano’s fury continues

Anatahan’s volcanic eruptions remained strong in the past few days, spewing out pyroclastic rocks and emitting volcanic smog hundreds of feet in the air.

The plume of smog extends to more than 370 nautical miles from the volcano and is below an altitude of 18,000 feet, according to the Emergency Management Office and the U.S. Geological Survey.

There was no report of any ashfall on Saipan, which is located about 120 kilometers south of Anatahan.

The EMO and the USGS said the eruptions have escalated in intensity but have become less frequent. The agencies recorded a few explosions per minute in the past days, less frequent than the occurrence of explosion every 3-10 seconds about a week ago.

“It is unlikely that ash is in the air more than a few kilometers from the island,” the agencies said.

An overflight conducted by the EMO more than a week ago saw ash plume rising to about 10,000 feet. The EMO’s overflight team observed pyroclastic rocks to have diameters of one meter or greater.

The volcano’s activity intensified beginning Jan. 4 after months of extremely low seismic activities, which followed the second batch of eruptions from April to June last year.

The volcano on Anatahan first erupted after centuries of dormancy on May 10, 2003, with ash plume rising to an altitude of over 30,000 feet that covered over 1-million-square kilometers of airspace above the Pacific Ocean and reached Philippine jurisdiction. That eruption, which ceased by mid-June that year, deposited about 10 million cubic meters of material over Anatahan island and the sea.

The second batch of eruptions began about April 9, 2004, after more than a week of increasing seismicity. The second eruption consisted of passive extrusion during mid-April, which later developed to strombolian explosions every minute or two on April 24, the agencies said. The strombolian explosions continued every minute or two through mid-July, often sending a thin plume of gas and ash upward a few thousand feet and 100 km downwind.

According to the agencies, the second eruption essentially 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.

Anatahan remains off-limits to the public, except for government and approved scientific missions, pursuant to a continuing emergency declaration by Gov. Juan N. Babauta.

Among the islands north of Saipan, Anatahan is the second closest, next to Farallon de Mendinilla. While the U.S. military has been using FDM for bombing practices, it had requested the Marianas Public Lands Authority to use a crater on Anatahan for military training, before the volcanic eruption happened in 2003.

Meanwhile, the Babauta administration pressed for federal funding for the installation of early warning devices and the implementation of volcano hazards assessment in the Northern Islands.

There are nine active volcanoes in the Northern Marianas, according to the USGS. In the seas off Maug island, the second northernmost island in the Northern Marianas, federal and local scientists who were part of the National Oceanic and Atmospheric Administration’s Oscar Elton Sette expedition sometime in September 2003 discovered a submerged volcanic crater that was showing signs of activity.

Although he allayed fears about the possible occurrence of tsunamis, EMO director Rudolfo Pua said the eruptions might result in such events if they become violent and send landslides to the sea. (With reports from Marconi Calindas)