Picture a cloud of superheated gas and rock racing down a mountainside faster than a speeding car. That is what hit the city of Saint-Pierre on May 8, 1902. Mount Pelee, a volcano on the Caribbean island of Martinique, had been showing warning signs for weeks. Steam rose from cracks in the ground. Small earthquakes shook the area. A lake inside the volcano's crater began to boil. Then on May 8, the volcano erupted with enormous force. Instead of flowing lava, it sent a deadly cloud of burning gas and ash called a pyroclastic flow. This cloud raced down the mountain at speeds over 100 miles per hour. The temperature inside the cloud reached more than 1,000 degrees. The entire city of Saint-Pierre was destroyed in under two minutes. About 30,000 people lost their lives. Only two people in the city survived. One was a prisoner locked deep in a stone jail cell. The thick walls protected him from the heat. The eruption of Mount Pelee taught scientists an important lesson. Not all volcanic eruptions produce rivers of lava. Some produce fast-moving clouds of gas that are far more destructive.