Mount St. Helens timeline

1978 -- United States Geological Survey geologists Dwight Crandall and Donal Mullineaux warn that Mount St. Helens has been "more active and more explosive during the last 4,500 years than any other volcano in the contiguous United States."

March 15, 1980 -- After a five-year period in which the mountain had 44 earthquakes, Mount St. Helens enters a week in which more than 100 are recorded.

March 21 -- Seismologists suspect the mountain is about to have its first eruption since 1857 but are reluctant to say so publicly.

March 27 -- Earthquakes become more frequent. Hundreds of loggers, Forest Service employees and residents are evacuated from a 1.5-mile radius.

March 31 -- Cowlitz County Commissioners declare a state of emergency. Cabin owners start complaining about being kept from their retreats.

April 1 -- Explosive plumes of steam and ash reach 20,000 feet.

May 18, 8:32:20 a.m. -- A magnitude 5.1 earthquake takes place one mile beneath the volcano. Rock and ice slide into the crater.

8:32:21 -- The bulging north flank begins to ripple, churn and slide away in blocks. A giant debris avalanche approaches speeds of 180 mph.

8:32:45 -- A huge explosion blasts out from where the north face slid.

8:33 a.m. -- The volcano, which one geologist calls a superheated champagne bottle shaken for two months, is uncorked. A lateral blast of rock, ash and hot gases heads northward.

8:33:20 -- The blast increases to nearly supersonic speed and overtakes the debris avalanche. Within an eight-mile radius, virtually everything is obliterated or carried away.

8:34 a.m. -- Within a 15-mile radius, everything is flattened. Fifty-seven people die, mostly by suffocating on hot ash. They are the first recorded fatalities from volcanic activity in the continental United States.

8:35 a.m. -- Mudflows of volcanic debris and water begin on Pine Creek, Muddy River, Swift Creek, the Kalama River and the South Fork of the Toutle River.

8:47 a.m. -- A vertical column of ash and steam rises in a mushroom cloud 12 miles above the volcano. The cloud generates lightning.

10 a.m. -- Ash cloud has reached Yakima, Washington. Darkness-sensitive street lights turn on.

11:45 a.m. -- Ash cloud has reached Spokane, Washington, 250 miles to the east.

1 p.m. -- Mudflows begin in the North Fork of the Toutle River as water-saturated parts of the avalanche begin to slump and flow. More than 65 million cubic yards of sediment are sent toward the lower Cowlitz and Columbia rivers.

3 p.m. -- Toutle River crests at 21 feet above normal.

5:30 p.m. -- Eruption subsides after ejecting 540 million tons of ash.

May 19 -- Bathtub-ring mudlines across the region show mudflows were on average more than 60 feet deep. Ash cloud arrives in central United States.

June 1 -- After circling the globe many times, most ash settles out. Some of the smallest fragments remain suspended in the upper atmosphere for years.

June 12 -- After several weeks marked by occasional steam and a nighttime glow from its crater, the volcano erupts again and forms a dome of lava on the crater floor.

July 22 -- Several eruptions destroy most of the dome. The volcano continues to have periodic eruptions into 1984, with the dome rising more than 800 feet. At the current rate of growth, it will take a century for Mount St. Helens to reach its former height.

Source: The Seattle Times