Bledug Kuwu mud volcano spouts salty water, local lore

Bambang M, Contributor, Grobogan, Central Java

Bledug Kuwu looks like just another muddy pond. But every one or two minutes, the placid water erupts in an explosion of mud, followed by a plume of white steam.

You can find this natural wonder near Kuwu village, 28 kilometers east of the town of Purwodadi. The pond is located just off the alternative road connecting Purwodadi and Cepu in Central Java, on a site measuring some 4.5 hectares. Bledug Kuwu has become a tourist attraction in the area.

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.

They have given the spots where the geyser erupts names as they believe that the place is sacred.

The geyser brings salty water up to the surface from the bowels of the earth. This water actually contains a higher level of salt than that of the sea.

Locals obtain salt from this water, and the visitor can watch the traditional process taking place. The salty, yellowish water that spouts from the earth is funneled along a bamboo channel to a teakwood container measuring four by four meters.

There are dozens of two-meter-long bamboo cuts joined together to form a channel of about 50 meters long. The water is then allowed to evaporate. Within one week, the water is all gone and all that is left is the salt.

"It's about 50 kilograms," said Suliyem, one of the salt workers, referring to the amount of salt she obtained weekly.

The salt produced this way is so tasty that it is said that the cooks from the old Surakarta Kingdom always used salt produced in this area.

Bledug Kuwu is a must-see spot though the area is almost devoid of tourist facilities. Despite the blistering heat, the pond is unique in the sense that it one of the biggest geysers in Java.

Jarot Setyowiyoto, a lecturer at Gadjah Mada University, said that there was also a pond in Djuwangi, Boyolali, which also was home to a geyser, although its eruptions were smaller. Larger eruptions also used to take place in Sangiran.

"Geologically, the phenomenon the you see in Bledug Kuwu is known as a mud volcano as it blows out mud from deep inside the earth," Jarot said.

He said that there were two possible explanations for the phenomenon.

First, a phenomenon known as a shale diapiric process, where the ground slowly sinks into the earth, thus producing eruptions.

Second, because gases from the earth or biogenic gases react and generate high pressure gas that has to find a way to escape to the surface.

The gas usually emerges where the soil is weak, such as in Bledug Kuwu.

"The gas build up under the mud. When the pressure is high enough, it pushes through the mud," he said.

And what about the salty water?

Jarot said that when the gas is seeking the way out, it passes through a layer of stone that geologically has trapped sea water underneath it for millions of years. The water is then pushed up to the surface by the pressure of the gas.

Such water usually has a high salt content. The water in Bledug Kuwu contains 8 ppm (parts per million) of salt, compared to the sea water which has a degree of 3 ppm.

Another interesting fact about the Bledug Kuwu geyser is that at the center of the eruptions, where the temperature is between 28 and 36 degrees Celsius, bacteria are found that are similar to one living in the depths of the ocean off Japan.

"The bacteria found there (in Bledug Kuwu) are extremely resistant. They are halotolerant, or capable of resisting high levels of salt," Endang S. Soetarto, a microbiologist from Gadjah Mada University, explained.

But the residents of Kuwu village know nothing about the bacteria or the scientific explanations for their geyser. If you ask them about the phenomenon, they will tell you about the legend of Aji Saka, the king of Medang Kamolan Kingdom, which stood close to Kuwu village.

It is said that the son of the king took the form of a snake, who was called Joko Linglung. Aji Saka was ashamed of his son. So he told Joko Linglung that he would only recognize the snake as his son if he killed his father's enemy, a white crocodile in the South Sea. The king also said that if Joko Linglung killed the crocodile, he should return home through an underground route.

Joko Linglung agreed and he finally managed to kill Dewata Cengkar, the white crocodile. He then crept home through an underground passage. Arriving in Bledug Kuwu, he emerged to the surface to take a rest and find out where exactly he was.

The locals believe that the hole from which he emerged is where the geyser now erupts, and the salty water is water from the South Sea which flows through Joko Linglung's underground passage.

Because the sound of the geyser erupting is like the explosion of a canon, the people called it Bledug, while Kuwu comes from the word pakuwon, which means "resting place".

Near Bledug Kuwu is the sacred grave of Mbak (Sister) Ro Dukun, or Raden Ayu Ngainah, the woman who took care of Joko Linglung when he was resting in the area.

The villagers believe that her spirit is still dwells in Bledug Kuwu.

"If the residents of Kuwu village want to hold a party, the must place offerings at Bledug Kuwu first. If they don't, then there will be problems," said Suliyem, a mother of two.

Whatever you think of this story, one thing for sure is that the salt produced at Bledug Kuwu is excellent.

"This salt can also cure stomachaches. Just put one teaspoon of salt in a glass of hot water and drink it," said Sukinan, Suliyem's husband.

Some villagers also sell the saltwater from Bledug Kuwu, which is said to also cure skin ailments. If you are skeptical, why not try for yourself at Bledug Kuwu.