In what year did the eruption of Mount St. Helens occur?

The eruption of Mount St. Helens occurred in 1980, which marked a significant geological event in the United States. This eruption was notable for its explosive nature and the large ash plume that resulted, dramatically affecting the surrounding landscape and ecosystem.

The 1980 eruption began on March 27 with a series of small earthquakes and steam-venting episodes, culminating in a major explosive eruption on May 18. The event had profound implications for volcanic research, environmental science, and emergency management, providing insights into volcanic activity and its effects on nearby communities.

This eruption has since been studied extensively, helping scientists understand volcanic processes and improve monitoring techniques for future volcanic activity. The other years listed—1975, 1985, and 1990—do not correspond with any significant or documented eruption of Mount St. Helens, reinforcing that 1980 is the accurate answer.