Universe Cycle - Geography (4)
Pre Lab 

  • Exploring the importance of soil on the Earth.
  • Comparing different types of soil.
  • erosion
  • laterite
  • pedalfer
  • pedocal
  • soil
  • temperate

Students use the internet to locate soil types.

New Jersey



Puerto Rico

Students have compared the difference between the Moon and the Earth. A major difference between the surface is the presence of soil on the Earth. Soil is a mixture of organic material and very small mineral and rock particles that can support rooted plant life.

The formation of soils is complex. Weathering of rock at the Earth’s surface breaks down rocks into pieces, and chemically dissolves them into different components. These weathering products form the inorganic ingredients of soil. The organic ingredients of soil, such as plant debris and animal waste, accumulate on the Earth’s surface.

Inorganic and organic components of soil mixed together in a variety of ways. As water sinks through the ground, it transports decayed organic material downward, where it mixes with weathered rock. Animals, like earthworms and moles, help to mix these materials as they dig tunnels.

Soils are a unique consequence of life on Earth. Other planets, particularly Mars, may have layers of weathered rock at their surfaces, but only the Earth has soils. Soils are present everywhere on the Earth where life is present or was present in the past. The specific type of soil that forms in a given area depends on three main factors. These include: 1) the type of rock available to be weathered, 2) the types of life in the area, and 3) the climate (temperature and rainfall).

Soil can be described and classified into different groups by soil scientists. Some classification are based on soil structure, color, organic content, and climate setting. We use a very simplified classification based on precipitation, to help students quickly identify and then plot the information. We use only three basic groups including pedalfers, pedocals, and laterites.

PEDALFERS - These soils are usually found in temperate areas that receive more than 60 centimeters of rain each year. They are very fertile, containing an abundance of aluminum and iron, and are a brown-black color. Pedalfers are present in much of the eastern half of the United States and most of Canada.

PEDOCALS - These soils are usually found in dry, warm climates such as those of the western United States, that get less than 60 centimeters of rain per year. The contain abundant calcium carbonate and many sulfate minerals. They are characteristically a light gray-brown color.

LATERITES - Laterites occur in warm, tropical areas that get more than 120 centimeters of rain per year. They have a distinctive deep red color, and contain much aluminum oxide and iron oxide. Oxidized iron gives laterite its red color.

Different color represent different typed of rocks.


This activity will have students discuss soil and how we can plot the type of soil on a map to see if there are any reasons for the pattern

  1. Ask the students to define soil. Many of them will just say "dirt." Give them an accurate explanation of what soil is, and how it forms. Make sure they realize that soil is a unique consequence of life and rock on the Earth, and that it is present throughout the world.
  2. Have the students locate themselves on the U.S. Placemats. Explain that there are different rocks throughout the United States. You may wish to point out areas of metamorphic, igneous, and sedimentary rock. Impress on the students that since there are many rocks on the surface of the United States (and the world) that there will be many different soils as well.

    Consult the following website for more information on rock types throughout the United States.  

  3. Define pedalfer, pedocal, and laterite soils for the students. Use the simplified definition in the background information.
  4. Use the following website to show students the different types of soil throughout the United States. You can look at the soils that are characteristic to each state.
  5. Here are some other websites on soil for more information.

    A cartoon based site at USDA, which introduces the basics of soil science. Very good for children.

    The "Soils of Canada" website. Good pictures of soils in cross-section. Very detailed technical information.

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