Clouds of deadly hot ash, rock fragments and volcanic gas surged down Mount Merapi's slopes Monday, as activity at the towering volcano intensified to its highest level yet. One of the eruptions sent an avalanche of debris and ash rolling almost four kilometers (2.5 miles) down the mountain's western flank, said Ratdomopurbo, the region's chief volcanologist. A string of other explosions throughout the day triggered other massive clouds. Many people who earlier refused to leave the danger zone fled in buses or trucks. Villages near the 3,000-meter (9,800-foot) peak resembled ghost towns, with only a few young men to be seen. Most houses, some dusted with ash, were deserted and shops closed.