Child Miners, 20th Century, United States

There are upwards of 560,000 abandoned mines on public and privately owned lands in the United States alone. Abandoned mines may be dangerous to anyone who attempts to explore them without proper knowledge and safety training. Old mines are often dangerous and can contain deadly gases. Standing water in mines from seepage or infiltration poses a significant hazard as the water can hide deep pits and trap gases below the water. Additionally, since weather may have eroded the earth and rock surrounding it, the entrance to an old mine in particular can be very dangerous. Old mine workings, caves, etc. are commonly hazardous simply due to the lack of oxygen in the air, a condition in mines known as blackdamp.
Records
As of 2008, the deepest mine in the world is TauTona in Carletonville, South Africa at 3.9 kilometers, replacing the neighboring Savuka Mine in the North West Province of South Africa at 3,774 meters. East Rand Mine in Boksburg, South Africa briefly held the record at 3,585 meters, and the first mine declared the deepest in the world was also TauTona when it was at 3,581 meters. The deepest mine in Europe is Bergwerk Saar in Saarland, Germany at 1,750 meters. The second deepest mine in Europe is Pyhäsalmi Mine in Pyhäjärvi, Finland at 1,444 meters. The third deepest mine in Europe is Boulby Mine England at 1,400 meters (shaft depth 1,100 meters).