【明報專訊】In 1980, a terrifying explosion blew the top off Mount St Helens (聖海倫火山) in the US state of Washington. Thousands of people might have been killed. Fortunately there were warning signs. People had time to leave their homes. Only 57 people died. But houses were ruined. Trees were reduced to piles of matchsticks. Lakes were filled with mud and rubble (碎石). Many wild animals died. And the landscape was changed forever.