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May 2020

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U.S. Census Bureau History: 1980 Mount St. Helens Eruption

Mount St. Helens

On May 18, 1980, Mount St. Helens, located in Skamania County, WA, erupted in one of the most explosive
volcanic eruptions in the United States during the 20th century. The blast laid waste to hundreds of square
miles of forest and killed dozens of people.

Mount St. Helens erupted as recently as 2008, and volcanic activity continues—including earthquakes and
an uplift of the ground as a result of a growing pool of magma beneath the mountain's surface. The U.S.
Geological Survey continually monitors and issues weekly updates about Mount St. Helens from the
Cascades Volcano Observatory.

Photo courtesy of the National Science Foundation.

On May 18, 1980, U.S. Geological Survey (USGS) geologist David A. Johnston radioed, "Vancouver! Vancouver! This is it!" from an observation post near the Mount St. Helens volcano. A massive eruption of Mount St. Helens had begun. The event would devastate hundreds of square miles in Skamania and Cowlitz Counties, WA; kill 57 people (including Johnston); destroy forests, lakes, highways, and homes; and spew an estimated 550 million tons of ash into Earth's atmosphere. Despite the passage of 40 years, the scarred landscape surrounding the volcano remains a testament to the power of the May 18 eruption.

Mount St. Helens lay dormant from the mid-19th century until March 15, 1980, when a series of small earthquakes signaled the volcano was reawakening. Steam eruptions created new craters on March 27 and 29. Scientists began recording tremors associated with magma movement on April 1, and Washington Governor Dixy Lee Ray declared a state of emergency on April 3 in response. Soon after, scientist detected that the mountain's northern face was bulging outward, raising 5 to 6 feet each day. This prompted Governor Ray to restrict movement within a "red zone" surrounding Mount St. Helens. By May 17, officials only permitted homeowners to retrieve belongings for a limited time as scientists recorded more than 10,000 earthquakes and witnessed regular eruptions of steam and ash.

On the morning of May 18, 1980, a magnitude 5.1 earthquake centered below Mount St. Helens' north slope triggered a landslide—the largest in recorded history—that sent the northern slope of the mountain sliding toward Spirit Lake and racing down North Fork Toutle River. That land mass had been acting as a cork containing magma, gas, and steam inside the volcano. The north slope landslide unleashed the high pressure gas and steam within the mountain, creating a pyroclastic flow of super-heated gas, steam, and rock that flattened 230 square miles of forest and created explosions of super-heated steam upon reaching Spirit Lake and North Fork Toutle River. Rapid melting of snow and glacial ice and the landslide's inundation of Spirit Lake created immense mudflows—known as "lahars"—that scoured the countryside, washing away roads, bridges, and vehicles. The lahar traveling down the Cowlitz River eventually clogged the Columbia River with nearly 4 million cubic yards of mud and debris and stranded ships going to and from Portland, OR.

Along with the landslide, lahars, and pyroclastic flows, Mount St. Helens sent a choking black column of ash more than 70,000 feet into the atmosphere. In just 9 hours, the volcano hurled more than 500 million tons of ash skyward. Within 90 minutes of the eruption, the ash cloud traveled 90 miles northeast to Yakima, WA, where it eventually blanketed the city in 5 inches of gray ash. By lunchtime, the ash traveled more than 350 miles to plunge Spokane, WA, into darkness. Ash fell on Jackson, WY, the night of May 18, and Denver, CO, the following day. Within days, a dusting of gray volcanic ash on fell on homes and cars in Rochester, NY, and Worcester, MA. In 2 weeks, the finest particles completely circled the Earth.

Fifty-seven people died as a result of the eruption on May 18, 1980. A memorial to them is located in a grove of trees on Johnston Ridge, at the site where USGS geologist David A. Johnston lost his life while observing the volcano during its 1980 eruption.

Mount St. Helens remains active, with minor volcanic earthquakes and eruptions of steam, gas, ash occurring as recently as 2008. You can learn more about volcanoes, Mount St. Helens, and the people and places its 1980 eruption affected using census data and records. For example:

Melted Pickup Dash

The explosive eruption of Mount St. Helens on May 18, 1980, took many victims by surprise because they believed they were outside the potential danger zone.
The U.S. Geological Survey photograph above shows the melted and ash encrusted dashboard from a truck that was nearly 9 miles away from Mount St. Helens
at the time of the eruption.

In the hours after Mount St. Helens erupted, the volcano hurled approximately 500 million tons of debris into the atmosphere, blocking sunlight hundreds
of miles away, and showering cities as far away as Boston, MA, and Augusta, ME, with gray ash. Finer particles of ash remained aloft for weeks, completely
circling the globe in 15 days.

Image courtesy of the U.S. Geological Survey

Active Volcanoes

The U.S. Geological Survey (USGS) reports that there are 169 potentially active volcanoes in the United States.

In addition to Mount St. Helens, the USGS monitors for volcanic activity at Yellowstone National Park, the Clearlake Volcanic Field near Kelseyville, CA; Mt. Rainer southeast of Seattle, WA; Great Sitkin overlooking Adak, AK; and Kilauea in the Pahoa-Kalapana Census County Division of Hawaii.

Willie Mays
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Did you know?

Fans may be unable cheer their favorite baseball teams due to the Covid-19 pandemic, but they can still learn study the sport using census data and records.

For example, did you know that baseball legend Babe Ruth hit his first Major League homerun 105 years ago this month; New York Yankee's "Iron Man" Lou Gehrig attended Columbia University on a football scholarship and studied engineering; or San Francisco Giants Hall-of-Famer Willie Mays played professional baseball before graduating from high school?

Learn more about baseball and many other topics using census data and records at the Census Bureau's History Website.

Geologists collecting lava
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A number of geology careers support the study of volcanoes. For example, volcanologist study volcanoes, lava, and magma; geophysicists use seismology (the study of earthquakes) to monitor volcanic activity; and geochemists study the chemical composition of volcanic rocks ash, and gases.

In June 2018, the Bureau of Labor Statistics reported that approximately 31,000 geoscientists worked in the United States. They earned a median annual salary of $91,130.

In addition to studying volcanic and seismic activity, geoscientists may also work as mining and geological engineers exploring for precious metals and petroleum products and oceanographers study underwater land masses.

Visit https://www.census.gov/history every month for the latest Census History Home Page!

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Source: U.S. Census Bureau | Census History Staff | Last Revised: February 16, 2023