Earth and Its Resources
Can you imagine a world without air? With no land? With no water?
Of course not! People couldn’t live without air to breathe, water to drink, and land to walk on. Those three things are some of our planet’s most important resources. Resources refer to all of the natural materials that help people live on our Earth.
In this lesson, we will find out more about the Earth’s resources and how we can use them wisely. Some resources can only be used once, such as oil, coal, and gas. People must learn to conserve those items. To conserve resources means that we should not waste them and use them sparingly.
Other materials such as iron, glass, and aluminum can be recycled. To recycle resources means to use them more than once. Both conserving and recycling are necessary if we wish to save our resources for the future.
Resources can be 1 of 3 groups
Reusable (use over and over) water, air
Renewable (can be made new again) plants, animals, sunlight
Non-renewable (only can be used once) oil, coal, natural gas, soil
Reusable Resources
First, some resources, such as water and air, are used again and again. They are reusable. The water that we drink and use for cooking and washing has fallen to the earth as rain many times in the past. And the air we breathe right now has been breathed by other people and animals before, and it will be used again in the future.
Renewable Resources
The second kind of resources is renewable resources. That means they can be “made new again”. They can be replaced. For instance, we eat plants and animals. We make clothes from cotton plants, and we can use cowhide to make leather shoes. But we can grow more cotton plants and raise more animals for leather. They are renewable resources. Sunlight is another renewable resource. Although we cannot produce sunlight, we can never use up the energy and light produced by the sun.
Nonrenewable Resources
The third kind of resource is nonrenewable resources. These resources can only be used once and then they are gone. Although the earth can make more of most of them, that process takes thousands or millions of years in many cases. Oil, coal, and natural gas are nonrenewable resources. Once we burn coal, it cannot be recovered or used again.
Soil is a nonrenewable resource. If we are careless with soil and let it wash from our fields into streams when it rains, we cannot bring it back. The soil settles on the river bottoms or eventually carried to the sea where it is lost to us. We call this soil loss erosion. Although new soil is formed when rocks are broken down into tiny pieces and mixed with dead plants and decaying animal matter, the natural process of creating new soil takes hundreds of years. If we are careful, however, we can keep our soil in fields and yards and use it for a long time.
Now let’s look more closely at some of these resources to see how we can use them wisely. Let’s look at two reusable resources first: air and water.
Air—A Reusable Resource
What is air? It is a mixture of gases. Gases are not solid or liquid. If we look at the air around us, we cannot see anything. The air is clear and colorless. But it does not mean that nothing is there. The molecules of the compounds that make up our air are moving very fast and are more spread out than in solids and liquids.
The air surrounding the earth is called the atmosphere. It is made up mainly of two gases, and there are tiny amounts of other gases present as well. We will study three of the most important gases in the air.
Nitrogen makes up 78% of the atmosphere. Oxygen makes up 21 % of the atmosphere. Carbon dioxide makes up less than 1% of the atmosphere. We can see that there is more nitrogen than anything in the atmosphere. People do not need nitrogen to breathe, but plants cannot grow without it.
We see that there is lots of oxygen in the air. People and animals need oxygen to live. Every time we inhale (breathe in), the air that enters our bodies contains oxygen. Our lungs capture the oxygen and move it through our bloodstream to the cells in our bodies.
When we exhale (breathe out), we release carbon dioxide into the air. Plants need carbon dioxide to live. The plants take carbon dioxide in through their leaves and release oxygen into the air in exchange.
As we look at these three gases even more closely, we see that plants, animals, and human beings use them in a balanced way. That is, there are cycles in nature through which these gases are renewed, so people never have to worry about running out of them. A cycle refers to something that occurs over and over in the same way.
Nitrogen Cycle
First, let’s look at the nitrogen cycle. Nitrogen moves from the air to the soil, where it is taken up by the roots of the plants and used for food. After the plants have died, the nitrogen is slowly released and returned to the air again. This cycle repeats itself all of the time. Nitrogen joins air when there is lightening during a storm. These nitrogen compounds are then carried to earth when it rains. Once in the soil, these nitrogen compounds are changed by bacteria into a form of nitrogen that plants use for growing. Bacteria are very tiny organisms that are too small to see without a microscope. The bacteria live all around us: in the air, in the water, and in the soil. When plants die, the nitrogen is separated from the dead plants by bacteria that eat the decaying plants. Then the nitrogen turns into gas and goes back to the atmosphere. We cannot see nitrogen, oxygen, or carbon dioxide, but the nitrogen cycle is going on around us all of the time.
The Carbon Dioxide and Oxygen Cycle
Now let’s look at another cycle. People and animal inhale oxygen and exhale carbon dioxide. Oxygen is needed by our bodies to help cells use the food we eat and turn it into energy for our cells. Carbon dioxide is left over in our bodies as a “waste product” that our bodies have to get rid of. On the other hand, plants need carbon dioxide to make their own food. They give off oxygen as a waste product.
We can see that oxygen and carbon dioxide are recycled or reused in a very natural way. Plants, animals, and people are all important in the process. Since nitrogen, oxygen, and carbon dioxide are so important, we need to be careful that we do not poison the atmosphere with other gases that could be dangerous to life. During the last 200 years, factories have been built to manufacture steel, chemicals, glass, and other products. Some factories require hot furnaces or ovens to make their products. Coal is burned as a fuel to provide much of the heat and energy these factories require. For instance, coal is burned in the steel factories to melt iron ore.
When coal is burned in older plants, smoke, water, and other gases are released into the air. One of these gases is carbon dioxide. If we release too much carbon dioxide into the air, we could upset the balance of the atmosphere.
The Greenhouse Effect
You may have heard of the greenhouse effect in the news. This has to do with the balance of the gases in the atmosphere. A greenhouse is a building with a glass roof and glass walls that trap the heat from the sun. The heat comes in, but it can’t escape due to the thermal properties of the glass and the heat capacity of the air. This keeps the inside of the greenhouse warm enough to grow certain kinds of plants and vegetables during cooler months for people and animals to eat.
In many ways the earth acts like a greenhouse. The gases in the atmosphere are like the glass building, trapping the sun’s heat near the surface of the earth. The greenhouse effect helps keep earth at a temperature that is warm enough for plants, animals, and people to live.
Several greenhouse gases, including ozone are carbon dioxide, act like a glass building trapping the heat. With too little of these gases, the earth would get cold. For example, the Year Without a Summer in 1816 or the beginning of the Little Ice Age. With too much of these gases, the earth would get hot.
Link: http://en.wikipedia.org/wiki/Little_Ice_Age
Link: http://en.wikipedia.org/wiki/Year_Without_a_Summer
When we burn coal, oil and natural gases, we are releasing more carbon dioxide into the air, and we are changing the balance of gases. The more carbon dioxide there is in the air, the more heat the atmosphere traps, and the warmer the earth stays.
How does coal, for instance, happen to have carbon dioxide in it that is released when coal is burned? That question has to do with how coal was made in the earth millions of years ago. Long before people lived on the earth, during the Triassic and Cretaceous periods (200 million years ago) there were larger plants than there are now. These first flowering plants grew to enormous size during the Triassic and Cretaceous Periods due to the warm global temperatures, the extremely high concentrations of carbon dioxide in the air for the previous 4.3 billion years of volcanic activity, and the abundance of more free water due to the higher temperature. Much of the land was still swampy. This means the ground was soft and wet. As the plants died, they fell into then swampy land and were covered with layers of sediment. Bacteria couldn’t make the plants decay underwater, and the plants were slowly covered with layers of more mud and sediment. After thousands of years, layers of sedimentary rock began to form over the dead plants, and slowly the water was squeezed out. The plants hardened into the hard, dark material, which we call coal.
Link: http://en.wikipedia.org/wiki/Evolutionary_history_of_plants
But the energy from the sun, which plants store for making food, was never released from the coal because the plants never decayed. Coal still has the energy stored in it. When coal is burned, (mixed with oxygen), the energy is released. Gases and other materials are released into the air. We call these gases pollutants. When the air is filled with pollutants, we say that there is air pollution.
Some of these gas pollutants combine with water vapor and rain to form acid. The gas molecules are combined with water vapor in the atmosphere to produce weak acids in the atmosphere. The acid falls with the rain and can damage buildings and plants. Then we have a problem with acid rain. In fact trees in some parts of the world are dying because of acid rain.
Courtesy of Mount Mitchell, NC Dept of Forestry
Car exhaust is also full of gases that change our atmosphere. As we drive more cars, build more factories, and create more pollutants, we are creating problems for ourselves. We have to keep our air clean so we can breathe it and so the plants can grow without harm.
Water—A Reusable Resource
Another resource we use over and over is water. When you think of all things we need water for, you might be amazed. We drink water and wash with it. We clean clothes and dishes. We water gardens and trees. Water is used for cooking. Water is used to produce medicines, clothes, machines, and even electricity. Water in a car radiator keeps the engine cool. In factories, huge amounts of water cool machinery. If we could not reuse water, we would soon run out.
Air and water are both reusable resources. We do not have to worry about running out of them, but we do have to try to keep the air and the water clean for future use. However many areas are experiencing drought due to the interruption of normal rainfall. The atmosphere undergoes normal periods of wet and dry. Depending upon the change in the climate, the weather patterns delivering water may also change.
Plants and Animals—Renewable Resources
Plants and animals both reproduce. That is they make more of themselves. Plants make seeds that grow into new plants, and animals raise young animals to take their place when they die. As long as people do not destroy of kill too many plants or animals of one kind, there will always be more of them.
However, renewable resources do need some protection. People have nearly killed all of the buffalo that used to live in the country. When the Native Americans were alone in North America, they were careful never to kill too many of any kind of plant or animal. The Native Americans only took what they needed to feed themselves. The Native Americans respected the balance of nature and lived in harmony with nature.
Today we need to respect and care for the plants and animals around us like the Native Americans did. For that reason, we have set aside national parks and forests where trees can grow without being cut down and where animals are not hunted. We also have laws to protect some animals whose populations are so low that they are in danger of dying out completely. We call these kinds of animals, endangered species. It is not legal for people to hunt or capture such animals. What are some endangered species? Eagles, certain kinds of whales, and buffalo are examples of animals that are protected by these laws.
Land or Soil—A Nonrenewable Resource
Soil is a nonrenewable resource. That is, it cannot be replaced if it is washed away by the rain, because it takes the earth a long time to make new soil. How is soil made? Over millions of years, rocks are slowly broken down into tiny pieces of sand. Dead plants (such as tree leaves, old corn stalks, or grass) and dead animals decaying on the ground are part of the soil.