Name: ______Date: ______Period:_____
Unit 2: Earth’s Land Resources
Section 4: Mining
Essential Questions: What processes form minerals? How are mineral resources extracted and what environmental impacts result from that extraction?
The ground beneath is in obviously useful for farming and ranching, but what other resources does the land provide? Believe it or not rocks, minerals, and the materials that can be removed from them are valuable resources. But they can be hard to find because most of these resources are hidden beneath the surface of the ground.
I. Minerals and Rocks
a. What are Minerals
All minerals are naturally occurring (1) inorganic (2) solids (3) that have an orderly crystalline structure (4) and definite chemical composition (5). They are used to make products as simple as the graphite in a pencil or as complex as a computer chip. Over 4000 minerals have been identified and many new ones are identified each year, but only about 1% are common in Earth’s crust.
To be a mineral, a substance must be formed by processes within Earth, on the surface of the Earth, or within organisms. Manufactured materials such as synthetic gems are not minerals. Minerals cannot have carbon-carbon or carbon-hydrogen bonds, which organic substances have as their base. (Coal is not a mineral because it was formed from once living material and contains these bonds.)
b. Mineral Formation
Minerals can form in a variety of ways in a variety of places.
1. Crystallization from magma or lava – As magma or lava cools, crystallization occurs and minerals can form. Molten rock that cools slowly forms large crystals and rock that cools quickly forms smaller crystals.
2. Precipitation – Elements and compounds that form minerals can be found in solutions. Minerals form from precipitation when the liquid in a solution evaporates and the remaining solids crystallize. For example, when water evaporates from shallow pools of ocean water, salt crystals can form.
3. Pressure and Temperature – When a mineral is subjected to great changes in temperature or pressure, its atoms may rearrange, causing it to become a different type of mineral. Carbon crystallizes into graphite, but under enough pressure and temperature (like in the mantle of the Earth) it can form diamonds.
4. Produced by Organisms – Some organisms form inorganic minerals to produce hard structures that provide protection and support. Examples are calcium carbonate in mollusk shells and calcium phosphate in the bones of fish and other vertebrates. When these organisms die, the remains of these organisms become sediments.
c. Rocks
A rock is a solid mass of minerals and mineral-like material that occurs naturally. Rocks can be made of one type of mineral or of many different types of minerals and other materials. Although rocks can seem unchanging, rocks do undergo dramatic transformations.
Convection currents in Earth’s outer core and the movement of tectonic plates cause rocks to sink deep below the Earth’s surface and rise again. During a very slow process called the rock cycle, rocks are heated, melted, cooled, weathered, and eroded as they slowly change between the three different types of rock – igneous, sedimentary, and metamorphic.
1. Igneous Rock – Rock that forms as magma or lava cools and solidifies.
2. Sedimentary Rock – Particles of rock that are blown by the wind or washed away by water eventually settle as layers of sediment. As layers of sediment build up over time, the weight on the earliest layers increases and compacts them. Over time, minerals crystallize, and like glue, bind sediment particles together forming solid rock.
3. Metamorphic Rock – When rock is exposed to great heat and pressure but not so high as to actually reach its melting point, changes occur in the crystals. Reshaping the crystals results in a change in its appearance and physical properties.
II. Mining
a. What is Mined?
Mining involves breaking into the ground to gain access to minerals, fossil fuel resources, or water, and extracting the resources. These resources are used in building materials, wiring, appliances, clothing, fertilizers, and an endless list of other goods. Without these resources, civilization as we know it would not exist. Although Earth has an immense supply of resources, they are not all accessible. Some minerals, such as silver, are widespread throughout the crust, but in such low concentrations in many places that mining it is not economically practical. One of the goals of mining is locating concentrated sources.
1. Metallic Minerals – A mineral or grouping of minerals that is mined so that a metal can be removed from it is called ore. Most ores are a mixture of the desired materials and rocky material having no value, which is discarded. Examples of ores include: gold, lead, iron, silver, and aluminum.
2. Nonmetallic Minerals – Many types of minerals are mined because the mineral as a whole has valuable properties. For example, sand and gravel may contain metals, but they are mined because they are valuable construction materials, not for the metal itself. About 44% of the sand and gravel mined in the United States in 2008 was used to make concrete. Gemstones are also considered nonmetallic minerals and can be extremely valuable.
3. Fuel and Water – Substances used for fuel sources are also mined. These include uranium, coal, petroleum, natural gas, oil sands, and methane hydrates. Most people don’t consider water to be mined, but whenever a well is drilled into the ground, that is exactly what you are doing!
b. Mining Methods
Complete this section of notes by using the links listed on the course resource website and the worksheet provided by your teacher. Below is a flow chart representing the process of mining.
c. Processing Minerals and Metals
Removing ores from the ground is just the first step in gaining access to the metals they contain. After mining, ores and other extracted materials are processed to separate the desired materials, combine them with other materials, or alter their properties. Once separation is complete, two products remain – the concentrated mineral and a waste product called tailings.
III. Mining Impacts and Regulation
The price we pay from an environmental perspective for the modern-day technologies and goods produced from mined resources is high. Destroyed habitats, air and water pollution, human health problems, and conflicts over limited resources are just a few examples of a long list of negative impacts mining has had on the environment and on the lives of many people.
a. Negative Impacts of Mining
1. Increased Erosion – When people disturb a large area of land, erosion occurs much faster than it would naturally. Soil is left bare and vulnerable to flash flooding, mudslides, and nutrient depletion.
2. Sediment and Debris – Some forms of mining result in a large amount of sediment and debris, which get displaced into valleys and streams nearby. This clogs waterways and results in damaged ecosystems.
3. Water Pollution – When certain rocks are exposed to oxygen, they react to form sulfuric acid. Acid drainage occurs as the acid and the metals it leaches from rock seep into groundwater or enter streams and lakes as runoff.
4. Air Pollution – Surface mining can cause air pollution as metal particles are released into the atmosphere. In dry areas of the world, tailings can be whipped up by the wind and carried far away. In subsurface mines, workers inhale toxic fumes and coal dust.
5. Possible Impacts of Undersea Mining – More mining companies are turning to the seas as land resources become scarce. Some scientists believe that excessive disruption of the sea floor will destroy habitats and organisms that have not been studied yet. Disruption of the sea floor may also cause toxic metals to enter the marine food chain.
6. Social Impacts – Many places in the world rely on the mining industry for jobs and revenue. But mining can have many negative effects on people living in surrounding communities including damage to infrastructure like roads and housing developments. Another huge problem is the conflict that is created between agricultural and mining communities. Violent conflicts can arise over the rights to lands that hold valuable minerals and how the wealth they generate should be shared, if at all.
b. Mining Regulation
Many people became rich almost overnight when large deposits of valuable metals were discovered throughout the United States in the mid-nineteenth century. Prospectors moved from area to area looking for the next big deposit of minerals such as silver and gold. Laws governing mining were limited in scope at this time. The mining industry continued to grow and the technology became more powerful and destructive to the environment. Eventually, laws became necessary to control who had access to these resources, the effects on the environment, and the safety of miners. Most federal laws governing mining are set up as guidelines for states to follow as they enact their own laws.
1. General Mining Law of 1872 – This law was enacted partly in response to the chaos of the California Gold Rush of 1849. It created some rules to manage mining activities, but it was also designed to promote mining. Miners must establish a claim to land and pay the government to lease it, but not any part of the profit. This law has changed very little since the time it was created except for the addition of use of public land for mining. However, many amendments have been suggested recently because of the increasing value of land and the resources it provides.
2. Mineral Leasing Act of 1920 – Because of the high value of fossil fuels, they are no longer considered to be under the same rules as other mined materials. Landowners must pay the government a leasing fee and royalties on the products they extract.
3. Surface Mining Control and Reclamation Act of 1977 – Because of the negative environmental effects of strip mining, the U.S. government now requires that coal mining companies “reclaim” or restore the land after mining is complete in the area. Companies who wish to mine must set aside funds for reclamation before they begin a new dig by buying bonds, which the government holds. If the company fails to restore the land, the government keeps the money and uses it to fix the land.
4. Mining Safety – Protecting miners from the hazards of their job has been an ever-expanding role of the federal government. It started with laws that prevented children under 12 from working in a mine and that mines must have proper ventilation. Over the course of United States history, thousands of miners have died, but the number gets smaller every year because of the increase in safety regulations. For example, 273 miners died in 1977 and that dropped to 53 in 2008. However, it is still considered to be one of the most dangerous jobs to have.
c. Responsible Mineral Use
Because minerals are a nonrenewable resource, we need to be concerned about finite supplies and ways to use them more responsibly, such as reusing and recycling. Like fossil fuels, at some point, there will be no more mineral deposits left to mine.
Many factors influence how long the reserves of a particular mineral will last. New technologies may make some minerals more in demand and others less in demand. Reducing, reusing, and recycling minerals addresses both the environmental impacts of mining and the limited supply of minerals. For example, roughly half the aluminum in use today is recycled which saves energy and money. Also, recycling some metals, such as mercury, means fewer of these toxic metals will end up in landfills.
Section 4 Review Questions
1. What are the 5 characteristics of a mineral?
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2. What two types of bonds are not in minerals (because they are organic)?
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3. How is the rate at which magma cools related to the size of the crystals in a mineral?
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4. Describe the process of precipitation of solids from solution. ______
5. Give two examples of how organisms use minerals for structure or support.
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6. True or False: The rock cycle is a relatively slow process. ______
7. What are the three types of rock?
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8. Place the corresponding letter of the source of each rock to its name above.
a. volcanic activity b. high pressure & temperature c. compaction of sediment
9. Describe how a rock can go through the entire rock cycle. Begin with a volcanic eruption.
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10. Complete the following sentence. Mining involves…______
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11. The first goal of mining is what? ______
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12. Why are minerals such as sand and gravel mined even though they have relatively low value? ______
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13. True or False: Not all of the steps of the mining process produce waste or tailings. ______
14. List the 6 overall negative impact of mining.
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15. Describe why creating mining laws became necessary over time.
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16. The first law established by the government required what 2 things? ______
17. Which law mentioned in your notes deals with the added requirements placed on fossil fuel mining? ______
18. In your own words, explain why the reducing, reusing, and recycling of metals and other mined resources is so important. ______
Section 4 Vocabulary
acid drainage – when acid and the metals it leaches from rock seep into groundwater or enter streams and lakes as runoff.
mineral – a naturally occurring, inorganic, solid that has an orderly crystalline structure and a definite chemical composition.
ore – A mineral or grouping of minerals that is mined so that a metal or metals can be removed from it.
rock – a solid mass of minerals and mineral-like material that occurs naturally.
rock cycle – an ongoing natural process where rocks are heated, melted, cooled, weathered, and eroded as they slowly change between three different types of rock.
strip mining – when layers of surface soil and rock are removed from large areas to expose the resource.
tailings – what is left of the land (soil, rock, organic matter, etc) after the resource is removed.
Unit 2, Section 4, Page 1