Okay I don't know if its just me but I think this is one of those things that will later require a, What Were They thinking Forehead Slap.

------First the background information.------

Indonesia will drop clusters of concrete balls into the mouth of a "mud volcano" in an effort to stop a mud flow that has swallowed villages and left more than 10,000 people homeless since it erupted eight months ago.

The plan to slow the mud flow with the cement balls is untested and has been controversial since three geophysicists at the Badung Institute of Technology announced it a month ago.

Each of the 1.5-metre-long chains will be connected to two 20-centimetre-diameter and two 40-cm-diameter concrete balls. Each chain assembly will weigh approximately 300 kilograms, and a total of 375 chains with 1,500 concrete balls will eventually be lowered into the main source of the hot mud.
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I would think the plan would do little to slow the flow of mud and might could actually increase pressure at the source of the flow, leading to another bigger eruption, or help create another route from which the mud could escape. Basically its like holding your finger over the hose making the water flow out at a higher velocity, except in this case there is a greater chance of the worse case scenario occurring. A Halftime show featuring The Artist Formally Known as Prince.

I will leave the Badung Institute of Technology alone for now until I learn more about them and what there deal is. And when I do I will smash there heads on my tum-may!