Alaska volcano blasts ash

September 01, 2007

Courtesy of Far North Science
By Doug O'Harra

Pavlov Volcano, a 8,261-foot cone rising from the Alaska Peninsula southwest of Anchorage, blasted a plume sparkling with lightning almost four miles into the sky on Aug. 30, continuing an eruption that began in mid-August and could be building toward a colossal explosion.

Photo of steam plume and incandescent lava at Pavlof, on the night of August 28, 2007, as seen from Sand Point.
Credit: Bill Rison / AVO

Although weather satellites did not detect ash, scientists at the Alaska Volcano Observatory say the presence of lightning in the plume suggests it carried gobs of the abrasive particles so dangerous to aircraft and jet engines.

The evening dispatch from AVO:

National Weather Service observers in Cold Bay reported a substantial plume and associated lightning emanating from Pavlof Volcano up to 20,000 ft (6,000 m) above sea level. The plume was also visible in images from the Pavlof web camera located in Cold Bay.

The web cam - one of several the observatory trains on its misbehaving volcanoes - went active this week and can offer a startling, other-worldly glimpse of the Pacific Ring of Fire at work.

Pavlof Volcano - one of the most active cones in the world - awoke Aug. 15 and began sputtering ash into the air, dribbling molten lava down its flanks and producing huge floes of mud, water and rock.

Pavlof summit viewed from the south on Aug. 18
Credit: Cyrys Read, AVO/USGS

The AVO continued to rate the volcano’s aircraft hazard at the Orange level and issued this statement:

If activity continues to increase in intensity, larger ash clouds that could affect higher-flying aircraft may be produced. The most immediate ground hazard in the vicinity of the volcano includes light ash fall on nearby communities.

Previous historical eruptions from Pavlof caused only a few millimeters (about 1/10th of an inch) of ash to fall on King Cove, Nelson Lagoon, Cold Bay, and Sand Point. Mudflows in drainages from the flanks of the volcano, and lava flows and avalanching of hot debris on the upper reaches of the volcano are also of concern in the uninhabited areas around the volcano.

Satellite and seismic data and eyewitness observations suggest most of the surface lava activity is occurring on the southeast sector of the steep-sided volcano; this suggests that the Pacific Ocean side of the volcano is at most risk from avalanching hot debris.

By the morning of Aug. 31, the volcano had quieted. In its latest dispatch, the observatory reported that Pavlov continued to tremble, but ash had not fallen on the nearby villages

Pavlov, the most hyperactive volcano in Alaska, has exploded at least 42 times since 1762 (and possibly 45 times), according to a Pavlof event timeline compiled by AVO scientists. Its dramatic snow-covered cone rises amid a cluster of other sister volcanos lurking around the Emmons Lake Volcanic Center near the tip of the Alaska Peninsula. Check out this large PDF file showing the complex and hazards.

Pavlof Volcano, on the map, is part of a chain of volcanoes
running down the Alaska Peninsula and out the Aleutian Chain
Credit: Seth Snedigar, Janet Schaefer, AVO/ADGGS

Alaska perches along the edge of the colossal collision between immense tectonic plates, the geologic process that creates the Pacific Ring of Fire. As the Pacific plate grinds beneath the North American plate - getting squished deeper into the Earth’s mantle at about the same speed as fingernails grow - the forces and pressures generate the magma that vent to the surface in one of the world’s great chain of volcanoes.

More than 100 volcanoes in Alaska have erupted sometime within the past 100 years, with 40 cones logging in blasts, spurts and explosions in historic times. Almost all of the U.S. volcanoes loom over Alaska horizons, including about 8 percent of the active volcanoes on the planet.

Most of Far North Science is written and edited by Doug O'Harra, a writer and journalist based in Anchorage, Alaska.