Mount St. Helens Eruption Timeline

A refined estimate of $1.1 billion ($3.5 billion in 2024) in damages was determined in a study by the International Trade Commission conducted at the request of the U.S. government.

Eruption debris created a resulting river depth of 13 feet that temporarily closed the busy Columbia River channel to ocean-going freighters, costing Portland, Oregon an estimated $5 million, equivalent to about $15.9 million in 2024.

Hundreds of square miles were reduced to wasteland by the eruption, causing over $1 billion in damage, equivalent to roughly $3.5 billion in 2024 dollars.

Backpacks belonging to missing victims were found in July 1980, but a layer of ash deposited by the eruption may have hidden their bodies, also preventing animals from disturbing the remains.

At least 25% of the timber destroyed by the eruption was salvaged after September 1980, as logging companies worked to recover valuable downed trees from the devastated blast zone.

According to Melanson's brother, in October 1983 Cowlitz County officials told his family that Melanson 'is believed [...] a victim of the May 18, 1980, eruption,' and after years of searching the family decided 'he's buried in the ash.'

In 2024, a study was conducted that provided an explanation for the observed phenomenon of an increase in the duration of the Lamb waves generated by the 1980 eruption compared to what was expected.

Decades after the eruption, research such as the 2024 Lamb wave study continues to draw on the wealth of data from Mount St. Helens, cementing its status as one of the most scientifically important volcanic events in modern history.

Mount St. Helens had remained dormant from its last period of activity in the 1840s and 1850s until March 1980, when renewed signs of volcanic unrest marked the beginning of a dramatic new eruptive era for the Washington volcano.

The main eruption was preceded by a series of volcanic explosions beginning in March 1980, signaling that magma was rising within the mountain and warning scientists and residents that a major eruption might be imminent.

In the weeks before the climactic eruption, pyroclastic flows occurred at Mount St. Helens as part of the escalating precursory activity, foreshadowing the devastating flows that would accompany the May 18, 1980 eruption.

Phreatic blasts, caused by groundwater flashing to steam as it contacted hot rock and magma, began in March 1980 and formed part of the sequence of precursor events leading up to the catastrophic May 18 eruption.

Governor Dixy Lee Ray issued an executive order on April 30, 1980 creating a 'red zone' around Mount St. Helens; anyone caught inside without a pass faced a $500 fine or six months in jail as authorities tried to keep people out of harm's way.

Following the May 18 climax, Mount St. Helens produced an additional five explosive eruptions between May and October 1980, prolonging the volcanic crisis through the rest of the year.

The 1980 eruption of Mount St. Helens was the first to occur in the contiguous United States since the much smaller 1915 eruption of Lassen Peak in California, making it a landmark event for American volcanology.

The May 18, 1980 event was the most deadly and economically destructive volcanic eruption in the history of the contiguous United States, claiming lives and causing enormous damage across the region.

On May 18, 1980, at 8:32 a.m., Mount St. Helens erupted catastrophically in Washington State, producing a lateral blast, ash column, pyroclastic flows, and lahars that transformed the landscape.

The sector collapse of Mount St. Helens' north face on May 18, 1980 was the largest subaerial landslide in recorded history, removing the summit and northern flank of the volcano in moments.

An earthquake at 8:32:11 am PDT on May 18, 1980 caused the entire weakened north face of Mount St. Helens to slide away in a sector collapse, unleashing the eruption that followed.

An eruption occurred on May 25, 1980, at 2:30 a.m. that sent an ash column 9 miles (48,000 feet; 14 km) into the atmosphere, one of the significant follow-up eruptions after the main event.