Poorly executed geoexplorational drilling opened a surface vent erupting mud and steam near Sidoarjo east of Surabaya (East Java, Indonesia) in May 2006. The mud has since then been flowing uncontrollably and covered more than 10 sq kilometers, displacing more than 10,000 people.

The mud volcano is informally also known as "Lusi" mud volcano. It is believed that it was triggered by the release of pressure from permeable limestone at a depth of 2830 m, which escaped through a gas well to the surface. The vent has been erupting mud at a rate of up to 150,000 cubic metres per day, and until today (2008) covered around 15 sq kilometers of land, destroyed several villages and forced the displayment of more than 12,000 people.