Sleeping giant wakes up 

10:35 PM PDT on Friday, October 1, 2004

From KING5.com Staff and Wire Reports

KING

MOUNT ST. HELENS, Wash. - After days of rumbling, Mount St. Helens unleashed a huge cloud of steam and ash – a spectacular sight that took many onlookers by surprise.

An explosion of steam and ground-up rock punctuated a week of small earthquakes at Mount St. Helens at noon Friday, but scientists said there could be more steam eruptions, possibly within hours.

Seismic readings within hours of Friday's steam blast on the volcano suggested that pressure is building up inside the mountain again.

The steam and dust cloud rose to almost 10,000 feet, but the explosion itself, which geologists characterized as "small" was almost anti-climactic from a distance, beginning as a small white cloud rising slowly from back side of the dome.

Closer views showed dark gray pulverized rock spraying into the air and blanketing the glacier behind the dome with a thick layer of ash.

Ashes settles as far away as Vancouver, Wash.

SkyKING also showed a 200- to 300-foot gash in the glacier behind the dome where the steam and rock came up.

Alaska Airlines canceled six flights scheduled to take off from or land at Portland International Airport and diverted three other flights headed to Seattle-Tacoma International Airport.

Before Friday's eruption, USGS Staff Geologist Jon Major said researchers discovered that the glacier on the south side of the dome where the explosion happened had developed some cracking, which scientists attribute to deformation happening underneath.

KING The steam explosion left a hole next to the dome inside the crater and blanketed a glacier there with ash.

The burst of steam began at 12:03 p.m. and lasted 24 minutes, according to USGS geologist Jon Major. Wind carried the plume to the west-southwest. Within a matter of hours, ash dust was reported in Vancouver, Wash. about 50 miles away.

Cynthia Gardner at the Cascades Volcano Observatory in Vancouver said it was the event scientists had been predicting because of earthquake swarms at the volcano.

Monitoring stations initially showed a drop off in seismic activity immediately after the eruption. Scientists said that if the seismic activity did not pick up again in a matter of hours, then activity at the volcano was probably over for a while. If activity picks up again, another eruption event is more likely.

One seismic monitoring station inside the dome was blown away by the explosion, according to University of Washington seismologist Tony Qamar.

FAA spokesman Mike Fergus said the FAA had sent out a notice to airmen to steer clear of the cloud, but that the cloud was not high enough to affect most air traffic.

Geologist Jon Major said there was a chance the eruption could just be the opening salvo and there could be more like it.

Major said the eruption was similar to the activity that was seen on the mountain between 1981 and 1985, but the eruption was not considered a dome-building event because there was no new magma deposited.

The May 18, 1980 eruption killed 57 people and blanketed much of the Northwest with ash. The most recent surge in activity on the mountain is now a week old.

The eruption comes after a week of tiny quakes that occurred Thursday and Friday at the rate of 3 or 4 a minute. Larger quakes with magnitudes of 3 to 3.3 occurred every 3 or 4 minutes.

The latest measurements showed the 975-foot lava dome in the volcano's crater had moved 2.5 inches to the north since Monday. Before the 1980 eruption, the north flank of the mountain swelled 5 to 7 feet per day.

The Geological Survey raised the mountain's eruption advisory from Level 2 to Level 3 out of a possible 4 on Wednesday, prompting officials to begin notifying various state and federal agencies of a possible eruption. The USGS also has asked the National Weather Service to be ready to track an ash plume with its radar.

The USGS has been monitoring St. Helens closely since Sept. 23, when swarms of tiny earthquakes were first recorded. On Sunday, scientists issued a notice of volcanic unrest, closing the crater and upper flanks of the volcano to hikers and climbers.

Scientists said they believe the seismic activity is being caused by pressure from a reservoir of molten rock a little more than a mile below the crater. That magma apparently rose from a depth of about six miles in 1998, but never reached the surface, Wynn said.

The mountain's eruption on May 18, 1980, blasted away its top 1,300 feet, spawned mudflows that choked the Columbia River shipping channel, leveled hundreds of square miles of forest and paralyzed towns and cities more than 250 miles to the east with volcanic ash.

Mount St. Helens timeline

1979: The mountain is a recreational haven. Half a million people a year visit the Spirit Lake area below the cone-shaped, 9,677-foot summit.

March 1980: The volcano begins to show signs of unrest. Earthquakes and steam eruptions continue for several weeks.

8:32 a.m., May 18, 1980: A 5.1-magnitude earthquake about a mile below the summit triggers a massive eruption and landslide, flattening 230 square miles of forest northwest of the summit and resulting in the deaths of 57 people. A plume of ash extends 15 miles into the sky and coats towns 250 miles away.

Summer 1980 - October 1986: Repeated minor eruptions build a 925-foot-tall dome of hardened lava inside the crater left by the eruption.

1982: Congress and President Reagan create the 110,000-acre National Volcanic Monument for research, recreation and education. Inside the monument, the environment is left to respond naturally to the disturbance.

AP Mount St. Helens belches ash and steam on Friday, Oct. 1, 2004, in this image from television more than a week after a flurry of earthquakes first warned an eruption was on the way.

1990: present: Steady progression in the variety and number of plants and animals returning to the blast zone.

1998: First major seismic activity since 1986, with earthquakes located as deep as 6 miles forcing magma to within about a mile of the dome, scientists believe.

2001: Another flurry of small earthquakes, but once again, no magma surfaces.

Sept. 23, 2004: The first of thousands of tiny, shallow earthquakes are recorded at St. Helens.

Sept. 26, 2004: The U.S. Geological Survey declares a notice of volcanic unrest, closing the crater and upper flanks of the volcano to hikers and climbers.

Sept. 29, 2004: Earthquakes increase to about four per minute, ranging in magnitude from 2.0-2.8. The USGS raises its warning system to the third of four levels and warns that a blast could send rocks and ash 3 miles from the summit.

Oct. 1, 2004: Mountain briefly belches out a plume of smoke and ash. Quakes subside.

Source: Mount St. Helens National Volcano Monument and the U.S. Geological Survey