Pictures: Lava Lights the Clouds

Mount Merapi spews lava high above the Indonesian island of Java Tuesday. Magma in the volcano is rising from depths of 4 to 5 miles (6 to 8 kilometers), versus 1.2 miles (2 kilometers) during its last eruption, in 2006, officials from Indonesia's Volcano Mitigation and Geological Disaster Agency said Friday—not a good sign.

"This is the scenario I dislike the most, because the deepest magma is pushing up now," Surono, the agency's chief, told the Australian newspaper Friday. "The eruptions haven't stopped, the tremors are getting stronger, and one big explosion could be the result."

Earlier: National Geographic Pictures: Merapi Eruption