Indonesia's most volatile volcano spewed ash and hot gas in a massive column as high as six kilometers into the sky. Mount Merapi's clouds of ash blanketed several villages on the main island of Java. A rumbling sound could be heard kilometers away. Villagers around were advised to stay three kilometers from the crater's mouth. The 2,968-meter-high mountain is the most active of Indonesia's 500 volcanoes. It has rumbled and generated dark hot clouds since last year. Its last major eruption in 2010 killed 353 people.