Weathering and Soils: The Nature and Properties of Soils

Classifying Soils

Whether you stand on Peruvian soil, Norwegian soil, Kenyan soil, Australian soil, Pakistani soil, American soil, or soil from any other nation makes a big difference in the properties present in the soil. Soils from all over the world are divided into twelve general categories, called soil orders cluetip icon . Soil orders are based on the main characterizing features of a soil, and they vary widely from dark, red, well-developed soils in the tropics to shallow, sandy soils of the deserts to frozen soils of the arctic tundra. The table shows the features of each soil order. After reviewing the table, view the world soil map to see where these soils are most prominent.

Please click on the Soil Orders Vocabulary link to share your way of remembering soil orders with your classmates. The discussion that you post on the whiteboard will not be graded. This discussion board is for your reference and will be a great resource to return to as you study for your quizzes and unit exam

Alfisols	Type of soil that forms under forests. They are usually fertile and have enough nutrients for good crop production.
Andisols	Young soils formed from volcanic ash. They are usually very fertile.
Aridisols	Desert soils that form in dry climates. They have very little organic matter.
Entisols	Young soils that are basically unaltered from their parent material.
Gelisols	Soils of very cold climates that are often frozen.
Histosols	Soils formed almost completely of organic materials. They are often mucky and moist.
Inceptisols	Soils that are slightly older than entisols but still highly resemble the parent material.
Mollisols	Soils that form under grassland. They have deep organic-rich surfaces and are important for agriculture because they have many nutrients.
Oxisols	Soils that form under tropical rainforests. They are reddish or yellowish and lack nutrients because the frequent rain washes all the nutrients out.
Spodosols	A type of soil that is usually sandy, light colored, and lacks many nutrients.
Ultisols	Type of soil usually found in warm humid subtropical areas.
Vertisols	Type of soil that has a high content of clay. Clay can shrink and swell, causing frequent churning and turning of these soils.

Why do you think entisols and aridisols are so common in northern Africa?

Entisols are very young and weakly developed soils. Because of the dry climate in northern Africa, there is little chemical weathering and little vegetation to aid soil development. Aridisols are the soils of dry climates, and again this area is largely a desert, so aridisols are common there.

What soil order is most common near the equator? How has this climate influenced soil development?

Soils near the equator are mostly oxisols. These are highly developed soils because of the high degree of weathering in the warm humid climate. Because of high rainfall, the soils are leached of many of their nutrients.