The earth has four layers. The center of the earth, or core, is made of very hot metal, mostly iron and some nickel. It has two layers. The outer core is liquid and the inner core is solid. The thick mantle comes next. It is made of rock--some of which has melted into magma. The rocky outer coating of the earth, called the crust, rests on top of the mantle. The crust doesn't cover the earth like a skin on an orange. It is separated into huge plates that are constantly moving.
Here's The Dirt
Over 70 percent of the earth's surface is covered by water. Most of the rest of the earth is covered by soil. Soil is made up of minerals from bits of rock, and decayed material from dead plants and animals. Most soil has two layers. The upper layer is called topsoil and this is the fertile layer where plant life grows. The bottom layer is called subsoil and is made mostly of weathered rock bits. Both layers of soil rest on hard bedrock which is part of the earth's crust.
Soil is one of the most important gifts of the earth. Soil supplies nourishment for plants. Who depends on plants for food? We do! And animals do too!
Plants, animals and humans need the minerals that are found in the soil.
Plants receive minerals through the soil. People get minerals from the plants they eat.
We also get minerals by eating meat, eggs and dairy products that are made from plant-eating animals. Minerals are an important part of a healthy diet.
Rocks Are Not Just For Eating
Minerals from rocks are needed for good health, but we use rocks in other ways too. Rocks provide us with strong building materials. Rocks are used in the construction of streets, homes, schools and other buildings in our communities. Common building stones are granite, limestone, slate and marble.
| FUN FACT: What's a rock? Some rocks are made of minerals. Salt is a rock made from a mineral called halite. Granite is a type of rock made from three minerals: quartz, mica and feldspar. Other rocks, like coal, are made from the remains of plants and animals that lived millions of years ago. |
Buried Treasures
Metal is a treasure that comes from the earth. Metals are mined, quarried, or dredged from lakes and rivers. Then they are made into products like furniture, keys, bikes, cars, tools and more. Precious metals like platinum, gold and silver are very valuable and important to businesses all over the world.
Glass comes from rocks and minerals too. Glass is made by heating sand and limestone together until they melt. When this mixture cools, it becomes glass. Look around the room you are in. What do you see that is glass? Mirrors? Windows? Your computer screen? It's amazing to think of all of the earth's gifts.
Hooray for Clay!
Clay comes directly from the earth and is made up of many small particles of rock. Water surrounds each particle and forms a moldable material that can be formed into shapes for different uses. When the clay dries, the water evaporates and the clay hardens. Not long ago, people had to make their own dishes and tools from clay. Today many people still enjoy creating their own clay kitchenware and ornaments. In addition, artists often use clay for sculpting and in paint-making.
If you'd like to make your own clay sculptures, check out Geo's EcoRama Cool Project. Go to Geo's Place at www.ecopals.com. Click on his Cool Projects icon, then the EcoRama icon.
An Art Box Down Under
Have you created works of art using materials from the earth? Many famous artists have. Each of these masterpieces were made using natural materials.
Ancient people used mixtures of earth and charcoal from their fire embers to do artwork on cave walls. Later, people made paint by mixing crushed rocks and animal fats. Today, artists still use clay, marble and other rocks for their sculptures. Many of their paints are made from minerals and talc found in the soil.
A Picture Is Worth A Thousand Words.
Long before pens and paper, people carved or painted pictures on rocks to tell stories about their lives. Have you ever "written" a message using only pictures and no words? This is exactly what ancient artists did on the walls of caves, the faces of rock cliffs and on huge boulders.
Rock carvings are called petroglyphs. Petroglyphs were created by grinding, scratching or pecking the rock's surface. Rock paintings are called pictographs. Powdered minerals, ground plants, charcoal and animal blood were used to "paint" pictographs. The pictographs that have survived until today are most often found in caves and other places protected from the weather. They have been discovered in North and South America, as well as other countries throughout the world.
The artwork of petroglyphs and pictographs can be seen at rock art sites and museums. If you would like to find out where these sites can be found in the United States, write to:
Petroglyph National Monument
123 Fourth Street, S.W., Room 101
Albuquerque, New Mexico 87102.
Rock art help us learn more about ancient times and cultures. You can create your own pictographs. The next time you want to share a message, try drawing a picture. Or, play Geo's Story Stone Game! It's at www.ecopals.com under the Games & Fun Page.
Other Earthly Wonders
Many of the world's wonders were created from rocks including the pyramids, Mount Rushmore and Stonehenge. The precious gems and stones that are used for rings and jewelry are also taken from the earth. These mineral treasures are valuable because they are hard to find and beautiful to look at. Gems like diamonds, rubies, emeralds and opals are known for their outstanding color and shine.
Hey! There's A Dinosaur In Your Gas Tank!
Fossil fuels are the decayed remains of animals and plants that lived in prehistoric times. Fossil fuels like coal, petroleum or natural gas were created about 300 million years ago because of the heat and pressure in the earth's crust. They are impossible for us to replace. This is why we call them nonrenewable energy sources. If we continue to use fossil fuels as quickly as we are, these limited energy sources will eventually run out.
You can learn more about fossil fuels and precious resources by visiting Geo's Special Feature. You can find a link to it on the first page of Geo's EcoInfo section in the interactive table of contents.
Cyber-Rock
Even your computer is made from the earth! Products from the soil, such as silicon, are used to create computer chips. Silicon is one of the most abundant elements in the earth. Your computer's plastic casing is made from oil which is taken from the ground. Your CD-ROM's have earth elements in them, too. The cables and wires have metallic material from the soil. Don't forget the other metals and your glass monitor. Even your modem line may be fiber optic and that's from the earth as well!
The Story Is in the Rocks
Geologists are scientists that study the rocks in the crust of the earth. They do this because they can learn about the earth's history. Rocks can tell a story that's millions of years old! Rocks let us know that once upon a time our continents were in different places, that land was frozen in ice, that volcanoes erupted, that certain mountaintops and deserts were once seas, that roaming dinosaurs turned to stone and that ancient people left us messages about their lives.
Related Books and Websites:
Would you like to learn more about dirt and the earth? Here are some books and websites that really rock!
Books:
James, Ian and Andrew Farmer. Planet Earth, (Great Britain: Dempsey Parr, 1998).
Symes, R. F. et al., Rocks and Minerals, (New York: Alfred A Knopf Inc., 1988).
Websites:
Visit the Kentucky Geological Survey site at:
http://www.uky.edu/KGS/coal/webrokmn/rocksmin.html
See the Smithsonian Museum's gems and jewels at:
http://www.bsu.edu/teachers/academy/gems/welcome.html