What caused the collapse?
It's not yet clear. Earlier this week, Chilean President Sebastian Pinera said the cause of the roof collapse, about 1,100 feet (350 meters) below the surface, is being investigated. The mine is owned by the Compania Minera San Esteban Primera, which along with the National Mining and Geology Service, has come under criticism since the accident. In 2007, an explosion in the San Jose mine is reported to have killed several workers. Prinera has said the mine should not have been reopened without an escape route, according to media reports.
What has hampered rescue efforts so far?
Two days after the roof of the mine collapsed and miners became trapped, rescue efforts hit a snag. Workers had been descending through a ventilation shaft toward a shelter, about 2,200 feet (670 meters) below the surface where the survivors were believed to be, when another cave-in blocked the shaft. The next day, Aug. 8, rescue workers began drilling bore holes, about 6 inches in diameter (15 centimeters), to locate survivors, according to Reuters.
On Aug. 22, more than two weeks after the initial collapse, the first bore hole reached the survivors, all 33 of them, who passed up a note, translated as: "The 33 of us in the shelter are well," according to Reuters. They received emergency rations and lights to stave off the darkness in the 540 square foot (50 square meter) room where they are living.
Why will it take so long to get the miners out?
To reach the miners, rescue workers will need to drill through a lot of rock. "It must be areas of fairly hard rock where the drill's going to have to drill through some pretty tough stuff," said Jeffery Kravitz, a U.S. Mine Health and Safety Administration technical expert.
Nevertheless, the drill will need to carve out a 26-inch- (66-centimeter)- diameter hole to pull the miners out. This task will be much more time-consuming than creating the bore holes, which were drilled to communicate with the miners and provide them with food and water.
How did 33 men survive 17 days trapped in the mine?
"The reason those guys stayed alive so long is they were extremely disciplined."
Once communication was established with the ground earlier this week, the miners reportedly explained they had rationed their supplies, limiting themselves to two spoons of tuna, sips of milk, a bite of crackers and a morsel of peaches, stretching supplies intended to last two days over more than two weeks with leftovers.
"That is a starvation diet," Gonzales said in a telephone interview. "What these guys were doing, they were just keeping their level of nutrition just above starvation, I am sure they all lost a lot of weight."
How is a gold and copper mine different from a coal mine?
Coal mines are typically a lot shallower than gold and copper mines. In the United States, gold and copper mines can go as deep as 8,000 to 9,000 feet (2,400 to 2,700 meters), while the deepest coal mines are only around 2,000 to 2,200 feet (609 to 670 meters) deep, Kravitz said.
Coal mines also usually run horizontal to the earth's surface, while gold and copper mines can run any which way.
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