Mount St. Helens, Wash. ? Mount St. Helens released a towering plume of ash Tuesday, its most significant emission in months but one that seismologists did not believe heralded any major eruption.

The volcano has vented ash and steam since last fall, when thousands of small earthquakes marked a seismic reawakening of the 8,364-foot mountain.

Eric Tolen and Bobbie Netling watch the eruption of steam and ash from Mount St. Helens Tuesday from a viewpoint in Rainier, Ore. Mount St. Helens released a towering plume of ash Tuesday, its most significant emission in months but one that seismologists did not believe heralded any major eruption.

Late afternoon television footage showed the plume billowing thousands of feet into the air, then drifting slowly to the northeast.

The ash explosion happened around 5:25 p.m., about an hour after a 2.0 magnitude quake rumbled on the east side of the mountain, said Bill Steele, coordinator of the Pacific Northwest Seismograph Network at the University of Washington.

Steele said he did not believe the explosion had increased the risk of a significant eruption and noted that recent flights over the volcano’s crater did not reveal high levels of gases.

Mount St. Helens rumbled back to life Sept. 23, with shuddering seismic activity that peaked above magnitude 3 as hot magma broke through rocks in its path. Molten rock reached the surface Oct. 11, marking resumption of dome-building activity that had stopped in 1986.