Open-pit mining which is also known as open-cast or open-cut mining and in larger contexts known as mega-mining is a surface mining technique of extracting rock or minerals from the earth from an open-air pit, sometimes known as a burrow or hole.
Open pit mining is different from extractive methods that are required to burrow a tunnel into the earth, such as long wall mining. These mines are used when deposits of commercially useful ore or rocks are found near the surface.
As we look at the environmental impacts of open-pit mining, let’s be aware that though open-pit mining is not practiced in all over the world, the impacts travel to places not even thought of though the immediate environment is adversely affected.
Table of Contents
What is Open-Pit Mining?
Open-pit mining, also known as open-cast mining is a surface mining method that extracts minerals from an open pit in the ground.
This is the most common method used throughout the world for mineral mining and does not require extractive methods or tunnels.
This surface mining technique is used when mineral or ore deposits are found relatively close to the surface of the earth.
Open pits are sometimes called ‘quarries’ when they produce building materials and dimension stones. Open pit methods have been utilized by Anglo America in its global operations.
For the open-pit mine to be created, the miners must determine the information of the ore that is underground and this can be done by drilling probe holes in the ground alongside plotting each hole’s location on a map.
The enlargement of these mines is done until either there is an increasing ratio of overburden to an ore which makes further mining uneconomic or the mineral product is exhausted.
When this occurs, the exhausted mines are sometimes converted to landfills for disposal as solid wastes.
However, some form of water control is usually required to keep the mine pit from becoming a lake, if the mine is situated in a climate of considerable precipitation or if any layers of the pit form the mine border between productive aquifers.
This mining has been considered to be one of the easiest and most beneficial techniques of mining by miners. Some of the benefits of Open-Pit mining include:
- It is cost-efficient
- It is easy to use for mass production
- It mines certain selected grades of ore
- It has a small crew size
- It helps in the elimination of safety hazards that comes with difficult underground mining operations
- It has easy drainage of subsurface water
- Any kind of machinery can be used both heavy and bulky machinery can be utilized
Places Where Open-Pit Mining Has Been Practiced
There places where huge open-pit mines have been located and practiced around the world all break different records and have been important in their respective country’s mining histories.
Here are some of the most impressive places where open pit mine has been practiced in the world.
- Escondida Mine in Chile
- Udachny in Russia
- Muruntau in Uzbekistan
- Fimiston Open Pit in Australia
- Kalgoorlie Mine in Australia
- Bingham Canyon in the United States of America
- Diavik Mine in Russia
- Betze-post pit in the United States of America
- Nanfen iron mine in China
- Aitik Mine in Sweden
- Grasberg in Indonesia
- Kimberly-Mine in South Africa
- Chuquicamata-Mines in Chile
1. Escondida Mine in Chile
Escondida is the third deepest open-pit operation in Chile. Escondida copper mine is located in the Atacama Desert. This mining operation is made up of two open-pit mines, namely Escondida Norte pit and Escondida pit. The Escondida pit is 3.9km by length, 2.7km by width, and 645m in depth. The Escondida Norte pit is 525m deep.
2. Udachny in Russia
Udachny diamond mine located in the Eastern-Siberian Region of Russia is currently the fourth deepest open pit mine in the world. The mining practiced at the Udachnaya kimberlite pipe has been going on since 1971. The mining pit is 630m deep.
3. Muruntau in Uzbekistan
Muruntau mine in Uzbekistan was discovered in 1958, it is the fifth deepest open pit. The mining operation at this site started in 1967. The Muruntau open pit is 3.5km long and 3km wide. The depth of the mine has reached just more than 600m.
4. Fimiston Open Pit in Australia
The Fimiston Open pit, located on the southeast edge of Kalgoorlie, Western Australia, is the sixth deepest open-pit mine in the world. The open pit mine is 3.8km long, 1.5km wide and up to 600m deep. It is also known as the Super Pit,
5. Kalgoorlie Mine in Australia
According to discovery, this is the second largest open pit gold mine in Australia, the Kalgoorlie Super Pit was built in 1989 after several underground mines were consolidated into one. The mine measures 3.5km long by 1.5km wide and is over 600 meters deep,
6. Bingham Canyon in the United States of America
The Bingham Canyon Mine, also known as the Kennecott Copper Mine. It is located southwest of Salt Lake City, Utah in the United States of America State. The mine was discovered by Mormon pioneers in the 1800s, it is the deepest open pit mine in the world at over 1.2km deep and covering an area of 7.7 square kilometers which can be seen from outer space.
7. Diavik Mine in Russia
The Diavik mine is located in the North Slave Region of the Northwest Territories Canada not as big as the Mirny Mine in Russia, this mine still produces 7 million carats of diamonds per year and employs roughly 1,000 people.
8. Betze-post pit in the United States of America
Betze-post pit is located on the Carlin Trend, Nevada, United State, and is the eighth deepest open pit mine in the world. The open pit is about 2.2km long and 1.5km wide. The depth of the pit is well above 500m.
9. Nanfen iron mine in China
Nanfen open pit iron mine is located in the Nanfen district of Liaoning province, China, and is approximately 500m deep. It is one of the largest open-pit metal mines in China.
10. Aitik Mine in Sweden
Aitik open pit mine is the largest copper mine in Sweden which is located about 60km north of the Arctic Circle in Northern Sweden and is currently 430m deep. The open pit is expected to reach a final depth of 600m. The mine also produces silver and gold. The mine was discovered in 1930.
11. Grasberg in Indonesia
Grasberg mine located in the Papua province of Indonesia currently ranks as the world’s seventh deepest open pit operation. The mine was set up by Ertsberg. It is 4,100 meters above sea-level
12. Kimberly-Mine in South Africa
Also known as ‘The Big Hole’, the South African diamond mine is the largest open pit mine that was dug by hand between 1871 and 1914 by 50,000 miners. With a depth of 240 meters and 463 meters wide.
13. Chuquicamata-Mines in Chile
The Chuquicamata Mine is one of the largest open pit copper mines in the world by volume and the second deepest open pit mine in the world at 850 meters. The site is located in the north of Chile. This mine has been in operation since 1910. It is also known as the Chuqui open pit, which is 4.3km long, 3km wide, and more than 850m deep.
Environmental Impacts of Open-pit Mining
Open-pit mining has been discovered to be one of the most dangerous surface mining techniques in the mining industrial world. It causes significant impacts on the environment, as well as damage to the health of miners. Below are the impacts of open-pit mining on the environment.
- Soil Erosion and Pollution
- Species Extinction
- Sinkhole Formation
- Habitat Destruction
- Noise and Light Pollution
- Deforestation and Vegetation Loss
- Water Pollution
- Air Pollution
1. Soil Erosion and Pollution
This is common to all types of surface mining techniques. To gain access to the mining area for excavating the minerals, the surface soil, rocks, and available vegetation. There is the disturbance of the topsoil which in turn causes soil erosion.
On the other hand, the rocks that were otherwise deeply buried get exposed to the atmosphere. After being broken and polished, these rocks eliminate harmful chemicals and radioactive substances. It highly affects the soil of that area and the nearby region
2. Species Extinction
Open-pit mining to a large extent has become more devastating to the environment by affecting our biodiversity. Most of the mining sites are densely populated areas for biological diverse species.
Which poses a serious threat to the existence and the sustainability of the species. While mining is vital for our economy, the effects of open-pit mining still raise questions about environmental conservation.
In mining activities, species go extinct as a result of huge land degradation and alteration. The pollutants produced during the process cause suffocation to the organisms present in that landmass.
Research has discovered that open-pit mining has influenced some endangered species substantially. And this is an important reason to consider imploring sustainable mining practices.
3. Sinkhole Formation
Sinkhole formation can be created during open-pit mining as a result of poor practices and this makes the environment vulnerable to damage. Sinkholes are the cavities formed after the deformation and displacement of the overlying strata. Some of the possible causes of sinkhole formation include weak earthquakes, overburden removal practices, geological disturbances, shallow depth extraction, rainfall, etc.
Sinkhole subsidence is one of the leading causes of surface structure (like buildings) damage. It can immensely affect the water flow. Other cavities can also affect vegetation and nearby habitats by releasing harmful chemicals.
4. Habitat Destruction
Habitats of diverse species in the environment are destroyed as a result of the processes involved in open pit mining.
Open-pit mines are excavated directly into mountain tops and as a result vegetation in that region is lost, the topsoil rocks are gone and the habitat is destroyed.
5. Noise and Light Pollution
Many open-pit mines take place seven days a week, and 24 hours per day this ensures the effective use of their expensive machinery and as such creates untold noise and light pollution which cause disturbance to humans and nearby wildlife.
6. Deforestation and Vegetation Loss
Alongside the removal of the topsoil rocks, vegetation is also lost on the other hand. Open pit mining’s environmental impact causes deforestation and vegetation loss causing an imbalance in the food chain and food webs.
Research shows that about 44% of mines are done in forest areas full of enormous biodiversity. And our work towards enriching the economy impacts the environment directly and indirectly. This further takes us to the leading cause of species fragmentation, threat, and habitat destruction.
7. Water Pollution
One of the most significant problems in open pit mining is also endemic to underground mining. An uncontrolled or unregulated mining activity leads to a heavy impact on our water bodies. The mining construction causes disturbance to the water body.
The mineral pyrite is often found in coal mines. It contains sulfur. When pyrite is exposed and sulfur reacts with air and water, it forms an acid. Acidic water as well as any rock-bound heavy metals that the acid has dissolved leach out of the mines and into nearby rivers, lakes, and streams, killing aquatic life and making the water unusable.
8. Air Pollution
Heavy clouds of dust form during mining operations. Blasting alone in the mining process is an enormous piece of the problem. The explosives used in blasting release fumes rich in smog and acid rain-producing gases like highly toxic nitrogen dioxide.
Some minerals in mining cause more damage to the environment than others. And one such devastating effect on the environment of open pit mining is air pollution. The production of minerals from ores after mining generates a large amount of harmful waste which, when it comes in contact with the atmospheric air causes air pollution.
Furthermore, respirable particulate matters and suspended particulate matters are pollutant products through open-pit mining. Which are more harmful than fumes from automobiles.
These are some of the impacts of open-pit mining on the environment. Mining activities are unsustainable not only because they exploit non-renewable resources, but also because they leave behind their destruction of the environment and society.
Unregulated mining processes leave behind the environmental dangerous effect which there is a very important reason for it to be addressed as this goes a long way to affect environmental sustainability.
As a result of the impacts envisaged in mining activities, there is a need for strict control measures to be put in place at all stages, from prospection, and exploitation to transportation, processing, and consumption.
After the excavation of mines, the miners should ensure mines are properly closed; and the land is properly rehabilitated and handed over to the land owners. Then they can start to earn their livelihood by cultivating their land.
Environmental quality is advised to be must be sustained in areas affected by mining. Therefore the designing and developing of environmentally sensitive strategies for extraction and land reclamation should be put into ardent consideration. This demands a more rigorous control of environmental impact assessment and more attention to ensuring productive and sustainable land restoration.
Furthermore, the government and other authorities should enact policies, and regulations and vehemently implement them to reduce the drastic influence of mining on our environment.
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Ahamefula Ascension is a Real Estate Consultant, Data Analyst, and Content writer. He is the founder of Hope Ablaze Foundation and a Graduate of Environmental Management in one of the prestigious colleges in the country. He is obsessed with Reading, Research and Writing.