Mt. St. Helens is an active volcano located in the state of Washington, USA. It is part of the Cascade Range and is known for its explosive eruptions. The most famous eruption occurred on May 18, 1980, when a massive explosion reduced the elevation of the mountain and created a large crater. The eruption of Mt. St. Helens had significant environmental impacts, including the destruction of forests and wildlife habitats. The area around the volcano is now a protected site, known as the Mount St. Helens National Volcanic Monument, which allows scientists to study volcanic activity and the recovery of ecosystems.