SEBASTOPOL College students were given a history lesson of a different kind yesterday when a 138-year-old mine shaft opened on their school grounds.
The mine shaft - the Band of Hope and Albion Consols Company number three shaft - was sunk in 1865 and is 128 metres deep.
It was one of 11 Band of Hope and Albion Consols Company mine shafts.
Almost 41,000 ounces of gold were pulled from the shaft.
Yesterday the mine shaft, which ceased operation in 1876, opened near the school's tennis courts.
The move burst a water pipe and left a large crater in the ground.
The crater measured about six metres wide and two metres deep.
Sebastopol College principal Garry Taylor yesterday said the reopening of the mine shaft was a historic moment for both the school and Ballarat.
Mr Taylor said the hole had grown from about one metre wide on Monday to six metres yesterday.
The drought combined with recent rain was believed to have caused the collapse, he said.
"We've always known that there's been a mine shaft in the area," he said.
"In March last year there was a drop in the level of one of the tennis courts, so we assumed it was there. This is about 10 metres away from the original depression.
"It's quite interesting - a bit of old history has resurfaced here."
Mr Taylor said a safety fence had been erected around the mine shaft and representatives from the Education Department and Primary Industries Department had inspected the area.
Civil engineers would today examine the mine shaft to determine the next course of action, he said.
"The civil engineers will take a look at it tomorrow and we will rely on their advice," he said.
"It will most likely require filling in, but how best that is done, we'll just have to wait and see."
Ballarat Goldfields senior project geologist Peter D'Auvergne yesterday said mine shafts were known to open unexpectedly.
"Often if it's a timber deck, which was usually the case, with time that rots away and when that happens there's nothing there to stop the soil on top of the cap from falling in," Mr D'Auvergne said.
"It's not a frequent occurrence, but they are alive.
"Unfortunately, we don't know where a lot of them are until they do open up."
The mine shaft at Sebastopol College is the third to reopen in Ballarat in the past two years.
Last October, an undocumented mine shaft opened in Ford St. It was believed to be part of the Black Hill lead.
In August, 2001, a Golden Point resident discovered a mine shaft under his bedroom when galvanised pipes burst at his Barkly St home.