If an earthquake was the cause, the eruption should have begun immediately, the scientists say.
Another unusual feature of the Indonesian eruption is that it involves a very thin, liquid mud, says Davies' colleague, Richard Swarbrick of Geopressure Technology Ltd.
That's unfortunate, because the thin mud could flow for long distances, increasing the devastation.
Also of concern is the fact that the mud is apparently being eroded out from deep underground, creating a cavern.
That means that the land around the volcano might collapse to form a crater, Swarbrick said.
The duration of the volcano's activity is also of concern.
Normally, mud volcanoes erupt quickly, then peter out to a slow ooze intermingled with the occasional major upwelling. But in Java the flow rate appears to have doubled since the eruption began, Swarbrick said.
At its center, the pancake-like deposit is already about 33 feet (10 meters) thick, Durham University's Davies added.
"It's carried on for a long time at a high rate, which suggests it's not going to stop tomorrow," he said.
Ultimately, the scientists say, they hope to learn more how to prevent such incidents from occurring in future oil and gas exploration.
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