FACTS ABOUT MOUNT ST. HELENS

8:32 a.m.

The eruption took place on May 18, 1980, at 8:32 a.m. PDT and was "the deadliest and most economically destructive volcanic event in the history of the United States," according to the National Oceanic and Atmospheric Administration.

57 people died

Autopsies showed that most of the people killed in the eruption likely died from asphyxiation after inhaling hot ash, according to the USGS. Fifty-seven people died including photojournalist Reid Blackburn, a USGS volcanologist named David Johnson and Harry Truman, an 84-year-old lodge owner who rose to fame after he refused to leave the mountain in the weeks preceding the eruption.

Two-month warning

The first sign that Mount St. Helens might erupt occurred on March 20, 1980, when a magnitude-4.2 earthquake caused snow avalanches to occur on parts of the volcano, according to the U.S. Geological Survey. Between then and May 18, there were more than 2,800 earthquakes recorded at the volcano and a bulge began to develop on the volcano's left side, PBS reported.

900,000 tons

Washington state worked to remove about 900,000 tons of ash from highways and roads, according to the USGS. The International Trade Commission determined the total cost of damage and rebuilding efforts from the eruption came to an estimated $1.1 billion.

230 square miles of damage

The eruption damaged roughly 230 square miles of land around the volcano, according to the USDA Forest Service. It destroyed 158 miles of highway, 200 homes and 15 miles or railways, the USGS reported.

About 7,000 big game animals lost

In addition to human lives lost, an estimated 7,000 big-game animals — such as deer, elk and bears — were killed. Birds and small mammals also died. The first animals to return to the eruption area were spiders and beetles. They were found at the site in late May 1980, according to the USGS.

110,000 acres

In 1982, the federal government set aside 110,000 acres of land impacted by the eruption known as the National Volcanic Monument. The land within the monument is protected and was allowed to naturally rejuvenate and restore itself.