Open-pit mining

People dig big holes in the ground.

They do this to find rocks and metals. These are found near the top of the earth.

Miners drill small holes to find the best spots. They use big machines to move the rocks.

The holes have wide steps on the sides. These steps help keep the walls safe. The big holes can even become lakes later.

It is a very big job.

Open-pit mining is a way to get rocks and metals from the earth.

This happens when useful ore is found near the surface. Ore is a type of rock that contains valuable minerals.

Miners often drill test holes to find these spots. They want to know how much ore is there.

To stay safe, the walls of the pit have wide steps. These steps are called benches. They help stop rocks from falling all the way down.

Large trucks use ramps to drive between these levels.

Mining can be hard on nature. It can cause dust in the air. This can hurt people's lungs. It can also lead to deforestation, which is when forests are cleared away.

When a mine closes, workers try to fix the land. This is called rehabilitation. They might cover waste with clay and soil. Then, they plant new green plants.

Some old mines even fill with water to become lakes.

Open-pit mining is a way to get minerals and rocks from the surface of the Earth.

This method is used when useful ore is found near the surface. Ore is a rock that contains valuable materials like gold or coal.

If the minerals are too deep, miners must use underground mining instead. Open-pit mines are often called open-cast or open-cut mines. Sometimes, people call very large mines mega-mining. These mines are very important for getting the materials our world uses every day.

To start, miners drill test holes to find where the ore is.

These holes help them see how much ore is there. They dig the mine in steps called benches.

These benches are usually 12 to 15 metres thick. They are also about 20 to 40 metres wide. This width allows large machines to work on each level. Miners use ramps to drive trucks between these different levels. The walls are often built at an angle to keep them safe. This helps prevent rocks from falling on workers.

Many different types of mining have been used over time. In the 1930s and 2000s, people used a method called untopping in Wales. This was done at Welsh slate workings. It helped miners reach minerals that were trapped under old underground mines. This made the old mines profitable again using new machines. Today, large mines can move almost one million tons of rock every single day. Small mines might only move a couple thousand tons in a day.

Mining can be very hard on the environment and on people.

It can create a lot of dust in the air. This dust can hurt the lungs of people living nearby. Mining can also cause deforestation, which is when forests are cleared. In 2024, nickel mining was a main cause of deforestation in Indonesia. Cobalt mining has also caused habitat loss in the Democratic Republic of Congo. Some mining waste, called tailings, is a liquid slurry. This waste is kept in special dams to protect the area.

When a mine is finished, workers try to fix the land.

This is called land rehabilitation. They might cover waste with clay and soil to stop acid from forming. Then, they plant grass and other plants to make it green again. Some old mines are even turned into artificial lakes. You can find these in the Lusatian Lake District in Germany. These lakes can become beautiful places for people to visit after the mining is done.

Open-pit mining is a surface mining technique used to extract minerals or rocks from the Earth.

This method, also called open-cast or open-cut mining, is chosen when valuable ore is found near the surface. In these cases, the overburden—the layer of soil and rock sitting above the ore—is relatively thin. If the mineral deposits are located much deeper, companies must use underground mining instead. When these operations reach a massive scale, they are sometimes referred to as mega-mining.

The process begins with careful exploration to locate the ore body. Miners typically drill a series of test holes into the ground. By analyzing these extracted samples, they can determine the extent of the ore and its commercial value. This helps them map out the specific location of ore veins or benches. Once the site is ready, the mining follows a structured mechanical process. This involves four main operations: drilling, blasting, loading, and hauling.

To maintain safety and access, open-cast mines are dug in a stepped pattern. These vertical levels are known as benches. Generally, large mine benches are between 12 and 15 metres thick. The width of each bench is determined by the size of the machinery, usually ranging from 20 to 40 metres.

Miners use a system of ramps to travel between these different levels. The walls of the pit are usually mined at an angle rather than being perfectly vertical. This angled section is called the batter, while the flat part of the step is called the bench or berm. These steps help prevent rock falls from traveling down the entire face of the wall. In some cases, workers use rock bolts, cable bolts, or shotcrete to provide extra ground support.

Managing water and pressure is a critical part of keeping a mine stable. If a mine is in an area with heavy groundwater, it may face issues like the bursting of the mine floor due to uplift pressure. Engineers use de-watering bores or horizontal drains to relieve this water pressure. This process is called depressurization. By removing tension from different areas, depressurization makes the mine more secure. This technique can actually extend the life of a mine by 10 to 15 years. Another technique used is annealing, which is the slow heating and cooling of a material to relieve internal stress.

Open-pit mining is a massive industrial undertaking with huge numbers involved. The largest mines can move almost one million tons of ore and waste rock in a single day. In contrast, small mines might only move a couple thousand tons daily. However, this scale brings significant environmental and health challenges. The process creates air pollutants from drilling, blasting, and transporting minerals. Inhaling these pollutants can cause lung issues and increase mortality rates. Furthermore, mining can lead to deforestation. For example, in 2024, nickel mining was a primary cause of deforestation in Indonesia. Cobalt mining has also caused habitat destruction in the Democratic Republic of Congo.

Waste management is another major concern for the industry. Waste rock is hauled to a dump, while leftover material from processing is called tailings. Tailings are usually a liquid slurry that is pumped into a tailings dam or settling pond. These dams can be toxic because they may contain unextracted sulfide minerals or cyanide, which is used to treat gold ore. When a mine is finished, companies may attempt land rehabilitation. They might contour waste dumps to flatten them and cover ore containing sulfides with clay. This prevents rain and oxygen from creating sulfuric acid through a process called acid mine drainage.

After a mine is closed, the land can be used in several ways. Some pits are converted into landfills for solid waste. Other sites are turned into artificial lakes, such as those in the Lusatian Lake District or the Central German Lake District. In some instances, a method called untopping is used. This involves removing the overburden from an old underground mine to reach minerals that were previously trapped. This technique was used in Welsh slate workings during the 1930s and 2000s to make old mines profitable again. While rehabilitation helps, it can take hundreds or even thousands of years for waste dumps to stop leaching acid into the environment.