In late May 2006, an unusual disaster befell part of the Indonesian island of Java: out of the blue, the area was flooded by a mud volcano. Not a mudflow racing down your typical spits-fire-and-ash volcano, but a natural eruption of mud. It’s been erupting ever since. Almost 40,000 people have now been displaced by the flood of mud, and almost $3 billion in damages and associated costs (like levee construction to limit the flooded area).