Bleduk Kuwu is a crater of mud in Wirosari area in Grobogan Region, Purwodadi, Central Java. Every two or three minutes, the placid water of Bleduk Kuwu erupts in an explosion of mud, followed by a plume of white steam. For local people, “bledug” means explosion and “kuwu” or “kuwur” means to be scattered. The place has been a tourist destination for decades.
Located several minutes by car from Blok Cepu mining site, Bledug Kuwu is somehow identical to the mudflow in Sidoarjo, East Java. If Sidoarjo's mudflow has displaced nearby residents and brought misery to the people, Bledug Kuwu has helped local people earn money. People living near this site make money by selling salt to visitors. The salt is harvested from volcanic sediment that is dried in an open field.
Visitors can watch the geyser from a distance of between 10 meters and 20 meters. The eruptions of water and mud shift positions from time to time, but there are two spots where the geyser regularly erupts. The locals call the one in the east Mbah (Grandpa) Jokotua and the one in the west Mbah (Grandma) Rodenok.
Legend has it that the explosion comes from a tunnel that connects the site to the mystical "Laut Selatan" or Indian Ocean. The tunnel is a passage for a mystical knight, Joko Linglung, and allows him to move between Laut Selatan and the Medang Kamulan Kingdom, the area of which includes today's Grobogan.
The natural phenomenon is caused by the release of gas, usually methane, from inside the earth bed.