Re: Does erosion cause laterite soil, and if so, can it occur in any soil type?

I am guessing from the form of your question that this is a homework question so I don't plan on "answering" it. I will give you some links.

I knew this question sounded familiar. (see: http://www.madsci.org/posts/ archives/dec97/877222328.Ot.r.html). I did find some additional stuff with my favorite search engine, AltaVista using +laterite +soil +composition as the search string. The copy of my earlier answer is kind of mangled so I cleaned it up:

From one website on tropical rainforests:

*       Nutrient poor soil 
*       nutrients locked in trees 
*       laterite = red soil 
*       brick-like if baked in sun"

"Most tropical forest soils are very poor and infertile. Millions of years of weathering and torrential rains have washed most of the nutrients out of the soil. More recent volcanic soils, however, can be very fertile. Tropical rain forest soils contain less organic matter than temperate forests and most of the available nutrients are found in the living plant and animal material.

Nutrient Recycling

Constant warmth and moisture promote rapid decay of organic matter. When a tree dies in the rainforest, living organisms quickly absorb the nutrients before they have a chance to be washed away. When tropical forests are cut and burned, heavy rains can quickly wash the released nutrients away, leaving the soil even more impoverished. ------end of quoted material.-----

Did you know that you can search the MadSci Archives?

Biochemistry of laterites described
Nice page on Central American Rainforests
Text from this website

Soils are products of weathering of rocks and other natural processes. Laterite soils form in specific conditions.

Soil and soil types

Soil: is any layer of weathered unconsolidated material on top of bedrock which may or may not support plant growth depending on the amount of leaching which has taken place. Soils are broken into soil horizons which are layers of soil distinguishable by characteristic physical and chemical products (including organic matter content). Character of the soil depends on the parent rock.

A typical soil profile will contain the following horizons:

Horizon A: Also called the zone of leaching is the darkest of the three zones due to the organic material called humus. It is a zone of intense biological activity, populated by everything from worms and insects to gophers, plant roots, and abundant microorganisms. Over time the soil gets thick and is void of any soluble minerals, leaving behind only clays and quartz.

Horizon B: Also called the zone of accumulation is the intermediate zone, the layers are characterized by accumulation on material leached downward from A. The soils contain little organic material but soluble minerals and iron oxides are present.

Horizon C: This is the lowest/deepest zone of the soil layers consisting of slightly altered bedrock which is broken and decayed then mixed with clays.

Soil types vary from region to region. In the eastern one half of the United States and Canada the region is considered as humid and retains a profile typical of a soil type called pedalfer. The soils are rich in quartz, clay minerals and iron oxide alteration products and are void of calcium carbonate. In the western one half of the United States where the climate is drier the typical soil type is called pedocal. Calcium carbonate is an important constituent of the soil as well as clays and unaltered silicate minerals. These soils tend to be less fertile. If this type of soil profile is found in a more humid area a subproduct called hardpan is associated with this horizon. Hardpan is a clayey layer of cemented soil. If this type of soil profile is found in a dry region then a subproduct called caliche (lime) forms on top from the movement of groundwater upward through the capillary openings due to evaporation at the surface. In tropical areas this type of profile would be consistent with a subproduct called laterite. It is generally found in the deep red soils of the tropics in which all silicates are completely altered leaving mostly al and fe oxides. Calcium carbonate and quartz have been leached, leaving only the most insoluble minerals. This is not a very fertile horizon for a long period of time, it is only good for a few years. If enough aluminum and iron are present bauxite will form. When laterite is exposed to the sun, it forms a bricklike texture and can be used as building material.

Regards,
David Winsemius