Thousands of abandoned mines scattered across South Africa are increasingly being viewed as a major environmental and public safety threat, with experts warning that ageing underground workings, rising mine water levels and illegal mining activities could trigger sinkholes, land subsidence and seismic events.
Researchers and mining specialists say the risks are growing in several former mining regions, particularly in Gauteng and Mpumalanga, where decades of extraction have left extensive underground voids and deteriorating infrastructure.
The warnings come as concerns mount over the pace of rehabilitation efforts and the long-term consequences of neglected mining sites.
Acid mine water and collapsing underground structures
Mining analyst David van Wyk said abandoned mines present a complex and escalating challenge.
According to Van Wyk, many former mining operations stopped pumping groundwater after closure, allowing underground tunnels and shafts to fill with water. Over time, this water reacts with minerals such as pyrite and sulphides, creating highly acidic conditions.
The resulting acid mine drainage gradually erodes underground rock formations, including dolomitic structures that help support surface stability.
As these geological supports weaken, the likelihood of sinkholes and ground collapse increases.
Van Wyk also warned that rising water levels in interconnected mining basins across Gauteng could contribute to tremors and seismic activity. The combination of water pressure and weakening underground pillars may eventually trigger collapses beneath the surface.
Areas identified as particularly vulnerable include Merafong, Khutsong, Randfontein and parts of Soweto, as well as Springs, Benoni and Boksburg on the East Rand.
Illegal mining adds to geological risks
The Council for Geoscience has acknowledged the land stability challenges associated with legacy mining operations and says it is working on mitigation and rehabilitation strategies.
Spokesperson Mahlatse Mononela said studies are underway to assess groundwater recovery, seismic activity and sinkhole formation in affected regions.
Geologists have also pointed to the role of illegal mining in worsening underground instability.
Large numbers of illegal miners, commonly known as zama zamas, continue to operate in abandoned shafts across the country. Their activities often involve the removal of supporting rock structures and the use of explosives.
Geologist Xolane Mhlanga identified the Witwatersrand gold basin and parts of Mpumalanga, including Barberton and Pilgrim’s Rest, as areas vulnerable to mining-related seismic activity.
Mining and environmental geology researcher Confidence Muzerengi explained that while mining tremors are generally much smaller than major natural earthquakes, repeated blasting and structural damage underground can reactivate geological faults and increase instability.
Experts argue that solutions should include improved monitoring, controlled blasting, shaft sealing and large-scale rehabilitation programmes.
The challenge remains significant. According to legal and environmental experts, South Africa has an estimated 6,100 abandoned mines, including more than 400 abandoned coal mines.
Critics argue that inadequate rehabilitation over several decades has left communities exposed to environmental hazards, unsafe land conditions and polluted water systems.
With many former mining regions continuing to expand residential and commercial development, specialists warn that delayed action could increase the risks facing future generations.
Source: The Citizen, Council for Geoscience