The Philippines' Mount Pinatubo is about to blow big. Is there enough time to evacuate the hundreds of thousands in its raging path? Stay with the scientists who remain behind- and see some astonishing footage of the world's largest volcanic eruption in 80 years. Local tribespeople were the first to see the signs. "There was a flash of light from the sky," said one. "I thought it was my time to die." The Philippines' Mount Pinatubo was acting restless- and the volcanologists at Clark Air Force Base were starting to sweat. An angry mountain is highly unpredictable. If they misread its fits and starts, a violent explosion could send pyroclastic flow- hot, dense avalanches- roaring down its sides at 100 miles per hour, burning everyone and everything in its path. But if they ordered an evacuation and nothing happened, these experts could lose their credibility for good. With a typhoon headed in their direction, the stakes are even higher. Torrential rains turn ash and rock into hot mud flows that can bury a town in minutes. Is it time to issue a Level 4 alert- ordering hundreds of thousands to flee their homes? Stay with the courageous scientists who remain behind- and see some astonishing footage as the world's biggest eruption in 80 years really starts to blow.