Earth Changes
The 3,676-metre Mount Semeru burst into life shortly after midnight but officials said it posed no danger to people living in the area, 35 kilometres southeast of Lumajang.
'We recorded that it erupted after midnight on Friday but luckily we have had rains so the ash isn't causing serious respiration problems for the residents,' volcanologist Agus Budianto told AFP.
The United States Geological Survey reported on its website the tremor measured 4.7 on the Richter scale, about 96 kilometres from Melbourne, and Geoscience Australia says the tremor was centred near Korumburra.
There have been no reports of injury and police are urging people not to call 000 unless they have been injured or suffered property damage.
Victoria Police and the State Emergency Service also say there has been an earth tremor but said there are no reports of any damage so far.
The quake, measuring 3.1 on the Richter scale, occurred at 3:06 p.m., according to the US Geological Survey.
It was centered two miles north northeast of The Geysers, three miles west of Cobb and six miles northwest of Anderson Springs, the US Geological Survey reported. It occurred at a depth of three-tenths of a mile.
Residents of Cobb, Middletown and even distant Fresno reported to the US Geological Survey that they felt the quake.
"Signals like this sometimes precede eruptions on the scale of hours to days, sometimes weeks or longer. And then sometimes the volcano just goes back to sleep," he said. "So you have to be cautious and assume that it may erupt and it could do so quickly, so that's the basis for our treating it with caution and changing the color code. On the other hand it could represent a new physical state of the volcano in which case it could do something different and then go back to sleep."
Heating caves "might be a way to keep the bats alive for a while until we come up with a cure or a solution," says lead author Justin Boyles.

An adult male mountain lion weighing between 120 and 130 pounds, in a tree near Spooner, Wis. The Wisconsin Department of Natural Resources attempted to sedate the animal with tranquilizer darts, but it escaped.
The animal, an adult male weighing between 120 and 130 pounds, was first seen Tuesday by a homeowner about 15 miles northwest of Spooner in Burnett County. Dogs were used to track the animal and chase it up a tree.
After the DNR was notified, officals from the department joined in the search, and on both Wednesday and Thursday the mountain lion was chased up trees. Two attempts to sedate the animal with a tranquilizer dart failed, and the mountain lion was not captured.
New Zealand's Institute of Geological and Nuclear Sciences said the quake, occurred at 03:41 a.m. local time (1441 GMT Wednesday), was centered 20 km east of Sheffield at a focal depth of 33 km.
There were no reports of casualties or damages.
The first shook the Los Altos Hills approximately 14 miles west of San Jose City Hall at about 11:15 p.m., and was recorded with the preliminary magnitude of 2.3, according to the U.S. Geological Survey.
A second earthquake with the preliminary magnitude of 2.6 reportedly hit the same region at about 11:45 p.m., approximately 13 miles west of San Jose City Hall.
The quake was felt around 9.50am today and measured 3.5 on the Richter scale.
It is the second-largest quake in SA this year and follows a magnitude 4.5 event north-east of Peterborough on January 26.
Primary Industries and Resources SA seismologist David Love said quakes in the ranges were not uncommon.
"Last year, about 250 earthquakes were recorded in the state and 80 per cent of lose were located in the Flinders and North mount Lofty Ranges," he said.