Porong, Indonesia ? For nine months, a gaping hole in the ground has spit out a biblical torrent of hot, black mud, swallowing thousands of homes outside Indonesia’s second-largest city and attracting amazed geologists from around the world.

Most say the flow is unstoppable, but Indonesian experts refuse to listen, and they have recently began carrying out a scheme straight from a Hollywood movie: dropping nearly 1,500 concrete balls into the mouth of the mud volcano.

“We know lots of people think this is a crazy idea,” said professor Satria Bijaksana, one of three geologists behind the $130 million plan aimed at reducing the spew of the sludge by as much as 70 percent. “But we think it will work.”

Mud volcanos are fairly common along volatile tectonic belts and in areas rich in oil and natural gas like Indonesia.

But the eruption just outside the city of Surabaya is exceptional because of the sheer volume of mud that has been surging each day from the hole – enough to fill 50 Olympic-sized swimming pools. Twelve villages and 20 factories have been swallowed, with mud-caked roofs and the tops of lamp posts as the only reminders of what once was there.

Some scientists suggest the rupture was triggered by improper drilling at a nearby natural gas site. Other research points to a major earthquake two days before the mud first appeared in a rice field in May.

The ball-dropping operation, which began last month, follows several failed attempts to contain or stop the mud.

Engineers are using a pulley system to hoist the beach ball-sized concrete spheres over the crater before dropping them from a height of about two stories. The balls, each weighing about 150 pounds, are chained together in clusters of four.

So far, nearly 150 have been tossed into the abyss, too few to make a real impact. The government has given them another five weeks to make a difference, or walk away and let the volcano run its course.