During the spring of 1980, scientists sensed that something was brewing deep inside Mount St. Helens. The volcano, located in Washington State, had been dormant—or inactive—for more than a century. Now it seemed to be rumbling back to life. Then on May 18, 1980, the volcano finally woke up. An explosion of hot ash and gases burst from its side and rushed down its slopes, killing 57 people and flattening 600 square kilometers (230 square miles) of forest. No one had expected an eruption of this size—or this level of destruction.