Open-pit mining is a type of mineral or rock extraction that does not necessitate tunnelling into the earth. When a desired mineral or rock is near the surface, companies typically opt for open-pit mining due to its lower costs and increased efficiency. Open-pits are typically dug in tiers and with angled walls to cut-down the risk of collapse or falling rocks. These holes can be tens of miles wide and thousands of feet deep. Generally these pits increase in size until the desired minerals are thoroughly depleted or the cost of extraction becomes too great.
Pro: Easier Extraction
The biggest advantage of open pit mining is the relatively low cost-extraction ratio. Open-pit mines are chosen when deposits of valuable minerals are found beneath the surface and where there overburden (overlaying rock or earth) is relatively thin. This means that no extensive tunnel network is required and no costly structural supports. Furthermore, large trucks can enter an open-pit mine, allowing for a more efficient transition from extraction to processing.
Pro: Safer Working Conditions
As open-pit mining requires no underground infrastructure, injury rates among workers are significantly lower. Cave-ins are virtually eliminated as risks; and build-up of toxic gases, which can cause sudden explosions or contribute to chronic illnesses, does not occur.
Pro: Consumer Benefits
Open-pit mining is significantly less costly than underground mining. Infrastructure and labour savings are passed onto the buyer of mined materials, which eventually trickles down to the consumer.
Con: Environmental Contamination
As with all forms of large-scale mineral extraction, open-pit mining can have a negative impact on the surrounding environment and ecosystems. The removal of the overburden destroys the pre-existing landscape and contributes to erosion. Moreover, chemicals used to treat extracted minerals --- for instance, cyanide used to treat gold ore --- can sometimes leak into the surrounding soil and water systems. Open-pit mines also require numerous roads and an accompanying production or treatment infrastructure.
Con: Human Health Risks
Tailing ponds are large contained bodies of waste water left behind after mineral extraction and treatment. Contaminated water sits in these ponds, which are usually lined with an impermeable material, until the water evaporates and the solid contaminants can be removed. However, these tailing ponds cannot always contain this waste if improperly made or maintained. This can result in the contaminants leeching into the soil or local surface and groundwater systems. Exposure to many of the chemicals used in mining can cause both immediate and chronic health problems.