Lesson plan
andisol
In USDA soil taxonomy, andisols are soils formed in volcanic ash and defined as soils containing high proportions of glass and amorphous colloidal materials, including allophane, imogolite and ferrihydrite. In the World Reference Base for Soil Resources (WRB), andisols are known as Andosols. Because they are generally quite young, andisols typically are very fertile except in cases where phosphorus is easily fixed (this sometimes occurs in the tropics). They can usually support intensive cropping, with areas used for wet rice in Java supporting some of the densest populations in the world. Other andisol areas support crops of fruit, maize, tea, coffee, or tobacco. In the Pacific Northwest US, andisols support very productive forests. Andisols occupy about 1% of the global ice-free land area. Most occur around the Pacific Ring of Fire, with the largest areas found in central Chile, Ecuador, Colombia, Mexico, the Pacific Northwest US, Japan, Java and New Zealand's North Island. Other areas occur in the Great Rift Valley, Kenya, Italy, Iceland and Hawai i. Fossil andisols are known from areas far from present-day volcanic activity and have in some cases been dated as far back as the Mesoproterozoic 1.5 billion years ago.
Article summary
In USDA soil taxonomy, andisols are soils formed in volcanic ash and defined as soils containing high proportions of glass and amorphous colloidal materials, including allophane, imogolite and ferrihydrite. In the World Reference Base for Soil Resources (WRB), andisols are known as Andosols. Because they are generally quite young, andisols typically are very fertile except in cases where phosphorus is easily fixed (this sometimes occurs in the tropics). They can usually support intensive cropping, with areas used for wet rice in Java supporting some of the densest populations in the world. Other andisol areas support crops of fruit, maize, tea, coffee, or tobacco. In the Pacific Northwest US, andisols support very productive forests. Andisols occupy about 1% of the global ice-free land area. Most occur around the Pacific Ring of Fire, with the largest areas found in central Chile, Ecuador, Colombia, Mexico, the Pacific Northwest US, Japan, Java and New Zealand's North Island. Other areas occur in the Great Rift Valley, Kenya, Italy, Iceland and Hawai i. Fossil andisols are known from areas far from present-day volcanic activity and have in some cases been dated as far back as the Mesoproterozoic 1.5 billion years ago.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
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