What causes Merapis eruptions to stop and start on a daily basis?
“You can compare a volcano to a can of spray paint in this case,” Wunderman said. “When it gets close to the end of the container, it doesn’t come out uniformly anymore, and that can be for a lot of reasons: If the nozzle gets clogged; maybe the upper part of the volcano has cooled enough, or has become congested.” Whether the clog gets unstuck depends on several factors, including whether or not there is enough pressure to push the material out and the volume of material there is to push out, Wunderman said. There’s also the distance that material has to travel. “The material has to travel 30 miles [48 km] to get to the surface; there has to be enough propellant force to push them all that way and out,” Wunderman said. The fact that Merapi is a stratovolcano also determines its rate of eruption, he added. “With many stratovolcanoes, there is a tendency to shove out stuff that isn’t that energetic, called a lava dome. The lava dome doesn’t flow, it just sits as an unstable blob on top,
