Mount St. Helens, in the Cascades Mountains in Washington State, erupted for 6 days beginning on May 18, 1980.
It immediately lost 1,314 feet (401 m) from its height and now stands at 8,363 feet (2,549 m).
The eruption was triggered by an earthquake (5.1 on the Richter scale) 1 mile (1.6 km) below the volcano.
Ash, lava, and debris from the eruption covered 231 square miles (601 sq km) of surrounding area, killing 57 people and more than 7,000 big-game animals such as deer, elk, and bear, not to mention countless fish, birds, and small mammals.
The trees it destroyed would have provided enough lumber to build 300,000 two-bedroom houses.
Now, more than 20 years later, plants have begun to return to the area, mostly because large numbers of elk and deer are once more passing through the area, depositing plant seeds brought from elsewhere.
In addition, trees are growing around Mount St. Helens again.
The U.S. Forest Service has planted 10 million trees on 14,000 acres (5,600 ha) of federal land in the area.
Over the next 25 years the renewal process will continue, and the slopes of Mount St. Helens will be green once more.